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MARCH 2013 ISSUE ▶ Eight Tips for
• Lifting Titan’s Veil Starting Right
• Predicting Auroras in Astronomy
• Remembering
Patrick Moore ▶ Binocular Basics
▶ Astro Product
March Audio Videos with
Sky Tour Image by Steve Yerby Dennis di Cicco
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 GREAT COMET IN MARCH? p. 50
T H E E S S E N T I A L G U I D E TO A S T R O N O M Y

Northern Exposure:
Take Amazing
Aurora Photos
p. 70

Titan’s Rain
Mystery p. 26
MARCH 2013

COSMIC
EXTREMES
The fastest planet & other oddities p. 18

Cosmic Jets in Your The Brightest Galaxy

Backyard Scope p. 36 You’ve Never Seen p. 60

Club Meetings
of the Future p. 32
Visit SkyandTelescope.com
Tele Vue Telescopes...
® Delighting Owners for over

Thirty Years – Fabian Neyer

“My first steps into astrophotography
were in 2002. I moved on to a full

“Heart and Soul” image taken with Tele Vue-NP101is and SBIG STL11000 CCD camera by Fabian Neyer. See full frame image and details at TeleVue.com
format CCD camera for deeper
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problem now was insufficient color
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In 2011 I finally bought my
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 March 2013 VOL. 125, NO. 3

On the cover: O B S E RV I N G M A R C H
Exoplanet HD 43 In This Section
80606b (whimsi-
cally depicted) 44 March’s Sky at a Glance
whips around its
host star 529,000 45 Binocular Highlight
miles per hour at By Gary Seronik
closest approach.
46 Planetary Almanac
S&T: LEAH TISCIONE
There’s more to find online @
47 Northern Hemisphere’s Sky
F E AT U R E S By Fred Schaaf SkyandTelescope.com
18 Cosmic Extremes
The universe is faster, colder, 48 Sun, Moon & Planets
COVER By Fred Schaaf FIND PRODUCTS & SERVICES
STORY and wackier than anything we Our easy-to-use directory will
can possibly comprehend. 50 Celestial Calendar help you find what you need.
By Bryan Gaensler By Alan MacRobert SkyandTelescope.com/directory

26 Where Goes the Rain? 54 Exploring the Solar System

By Thomas Dobbins
Saturn’s moon Titan has a
mysterious weather cycle. 56 Deep-Sky Wonders
By Donald F. Robertson By Sue French

60 Going Deep
32 Revitalize Your Club Meetings By Steve Gottlieb
Webinars can add variety and depth
GEMINI
to your club gatherings — without
S &T T E S T R E P O R T
breaking the budget.
By Tom Field 62 S&T Test Report
By Dennis di Cicco
36 My Hunt for Cosmic Jets
ALSO IN THIS ISSUE
A crucial phenomenon throughout
6 Spectrum
the universe is visible in amateur
scopes, but just barely.
By Robert Naeye SKY AKIRA FUJII
WEEK
By Dave Tosteson 8 Letters

9 75, 50 & 25 Years Ago SKYWEEK

70 Northern Exposure Watch our weekly PBS segment
Follow these simple suggestions to By Roger W. Sinnott
on what’s currently up in the sky.
take stunning aurora photographs. 10 News Notes skyweek.com
By Babak A. Tafreshi
40 New Product Showcase
MONTHLY SKY PODCAST
Special Report: Page 16 67 Telescope Workshop Listen as we guide you through
By Gary Seronik this month’s celestial sights.
We Remember
Sir Patrick Moore 76 Gallery SkyandTelescope.com/podcasts
Patrick Moore was the
face of astronomy for
86 Focal Point TIPS FOR BEGINNERS
many in Britain —
By Steve Lewis
and around the world. New to astronomy?
By Timothy A. Lyster Here’s everything you
need to jump into the fun.
SkyandTelescope.com/letsgo
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Robert Naeye
Spectrum Founded in 1941
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The Essential Guide

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EDITORIAL

Eclipses Past & Future

Hed.GillSans.30
Editor in Chief Robert Naeye
Senior Editors Dennis di Cicco, Alan M. MacRobert
Associate Editor Tony Flanders
Imaging Editor Sean Walker
Assistant Editor Camille M. Carlisle
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Editor Emeritus Richard Tresch Fienberg
Senior Contributing Editors J. Kelly Beatty, Roger W. Sinnott
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Contributing Photographers P. K. Chen, Akira Fujii, Robert Gendler,
Babak Tafreshi
ART & DESIGN
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I write these words in early December, shortly after returning Illustrator Leah Tiscione
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Editor in Chief
6 March 2013 sky & telescope
 Letters
Write to Letters to the Editor, Sky & Telescope,
90 Sherman St., Cambridge, MA 02140-3264,
or send e-mail to letters@SkyandTelescope.com.
Please limit your comments to 250 words.
Astronomical Feast hear a pin drop while they watch. They
The picture of Per Collinder and col- especially liked the “sea goat” broadcast
leagues in the December issue’s “Explor- from last October. I learn something new multiverse that astrophysicists are try-
ing Those Odd-Named Star Clusters” every Monday when we watch the latest ing to detect the same one that quantum
(page 39) in fact shows not a lobster episode together. computer theorists exploit? If it is, are these
dinner but a traditional Swedish crayfish Dwight Wells other universes considered to be far away,
party (Astacus astacus, now unfortunately Shanahan Middle School or right next to us, perhaps even interwo-
at a high risk of extinction in the wild). Lewis Center, Ohio ven with ours?
The crayfish party is traditionally held At age 61, I hope I live long enough to
in mid-August, shortly after the legal Editor’s Note: We’re tickled pink to think of see some kind of resolution to the multiple
opening of the harvesting season. On the Tony as a rock star. Around here he’s more universe issue, but I suspect that the true
table sit the dish of crayfish, the beer, and often seen as the man who rides his scooter nature of the universe is always going to
conical aquavit glasses. Judging from the down the hall. prove slightly more elusive than we think.
stern faces, the picture was taken early in Tom Sales
the evening. Multiple Universes Somerset, New Jersey
I hope you do not take my note as more I really enjoyed Camille Carlisle’s multi-
serious than I mean it to be — just a note verse article (December issue, page 20). Author’s Note: No, the quantum multiverse
about a quaint Swedish tradition. It seems like whenever I read articles that and the cosmological one are not the same.
Nils Olof Carlin expand my knowledge of a subject, I have Several different developments in theoretical
Skövde, Sweden trouble understanding them and tend to physics have raised the multiverse issue, but
fall asleep — but Carlisle’s article, in spite each theory envisions the multiverse in distinct
SkyWeek Celebrity of the complexity of the subject, was very ways. (Apparently, there are multiple ways to
I just wanted to drop you a line on behalf understandable. It amazes me that just invoke multiple universes.) For example, in
of my eighth-grade earth science class a few hundred years ago we considered some versions of the “many worlds” interpreta-
and say thank you for your website, and the solar system to be the universe. Later tion of quantum mechanics, every time an
especially the weekly SkyWeek webcast it was our galaxy, then the Big Bang uni- experiment is run and we see one result before
featuring associate editor Tony Flanders. verse, and now the multiverse. us, another reality splits off from ours in which
Tony has rock-star status with my kids and Darryl Davis a different result occurred. It’s unclear where
has inspired many of them to download Albany, Oregon that reality would “exist” — concepts such as
apps so that they can interpret the sky at “next door” or “far away” don’t really apply.
night. I started showing the videos last I was taught that an indication of the On the other hand, the pocket universes of
year and all the kids love them — you can weakness of the Ptolemaic system of the cosmological multiverse I discussed are
astronomy was the addition of a few distinct patches of spacetime that came into
epicycles to make the theory fit the data. being independent of one another. From our
Now, however, it seems we can have 10500 perspective inside our bubble universe, these
additional universes to allow string theory other bubbles are infinitely far away. One
to be correct. Now that is inflation! way to think of the difference between the two
Andrew Smith frameworks might be to compare a bubble
Delamere, United Kingdom bath and a branching tree. I recommend
Brian Greene’s book The Hidden Reality for
I didn’t understand the multiverse before more information: he looks at several multi-
(and frankly still don’t), but you clarified for verse theories and talks about their differences.
me how astrophysicists view the concept.
I haven’t read an article this interesting I loved Camille Carlisle’s article “Cosmic
since the 1980s, when Scientific American Collisions.” She did an exemplary job of
did a piece on how the concept of multiple putting abstruse material into laypersons’
universes lay behind advances in quan- terms. At one point, though, she wrote
tum computers. In that case, a multiverse that “The universe . . . [grew] to be at least
would be the connection between quantum 1,000 times bigger than the universe we
mechanics’ probabilistic weirdness and can actually observe.” How can the uni-
S&T: LEAH TISCIONE our concrete, one-result experience. Is the verse be bigger than what we can observe

8 March 2013 sky & telescope

if we are now able to observe (almost) back like the world has an edge, but that’s because
to the Big Bang? you can only see the light that reaches you.
Joel Marks The same thing goes for the “surface” of the
New Haven, Connecticut CMB: it’s an edge in the sense of being a hori-
zon. The physical radius of this horizon is

QSI • SBIG • SKY-WATCHER USA • SOFTWARE BISQUE • STARLIGHT FOCUSER • STARLIGHT XPRESS
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Author’s Note: Basically, we don’t observe not 13.7 billion light-years, but about 45 bil-
the real edge of the universe, we only observe lion light-years. However, inflation requires
our horizon. There are two points. First, the that the observable universe is a tiny patch of STi
cosmic microwave background isn’t a real a larger region of spacetime. How large that
edge: it’s a glow suff using the whole universe, region is, we don’t know.
coming at us from all directions. Second,
light has only had about 13.7 billion years to For the Record
travel, so we can only see parts of the universe ✹ The Byurakan Observatory mentioned on
from which photons have been able to reach page 38 in the December issue is in Armenia,
us in that time. A loose analogy would be not Georgia as stated.
standing on Earth’s surface, where you only ✹ Asteroid 6 Hebe occulted a star, not the
see what’s within your horizon. It might look other way around (December issue, page 29).
LX850

75, 50 & 25 Years Ago Roger W. Sinnott

Rich View
March 1938 “During the next few years, the pair will SolarMax II
Old-Fashioned Winters continue to widen. Even with large telescopes,
“The Leander McCormick excellent seeing and first-class optics are
Observatory [in Charlottes- required to show the elusive Sirius B.”
ville, Virginia] . . . is a U.S. This note in the “Observer’s Page” is also apt
Weather Bureau Station. now: Sirius B’s period is 50.09 years, and it has
The director himself makes returned to the same point in its elongated orbit
CGE Pro 1400 HD
CG
the weather observations as it was when this note appeared in 1963.
each day. . . .
“The sage of [nearby] Monticello, Thomas March 1988
Jefferson, was himself an indefatigable weather Phantom in M31 “At the
observer . . . [and wrote in an 1804 publication]: ‘A Central Bureau for Astro-
nomical Telegrams we are

SS • TAKAHASHI • TELE VUE • THE IMAGING SOURCE • VIXEN PLANEWAVE

change in our climate is taking place very surely.
Both heat and cold are becoming more moderate responsible for announcing
within the memory of even the middle-aged, and to the world discoveries of
snows are less frequent and less deep.’ . . . transient astronomical phe- Veloce RH 200
“For Charlottesville, both the summer and nomena. . . . Let me share Now available!
the winter records show unmistakable signs with you the events of last 8" f/3.0 astrographh
that the temperatures are on the average now November 24th, a day I call . . . Black Tuesday.
warmer than they used to be in 1900. . . . As “[My] colleague Dan Green shows me a telex
far as one can see off-hand, there is no reason claiming the discovery three days earlier of an
whatever for this continuous increase.” 11th-magnitude supernova in M31, the Androm-
Samuel Alfred Mitchell, an expert on stellar eda galaxy, by Crimean astronomer Nataliya
parallaxes, directed McCormick Observatory from Metlova. . . . The rumor spreads like wildfire, Drive Master
1913 to 1945. and soon astronomers everywhere appear to be
gearing up to observe the supernova. . . .
March 1963 “It occurs to me that more astronomers
Sirius B “[T]he faint must have wasted more time on Black Tuesday
companion of Sirius has
receded far enough from its
than on any other single day — all because one
erroneous report was ‘leaked’ to the scientific Telescopes.net
dazzlingly bright primary to community before it was confirmed. I worry that
become visible in moderate- today’s instant communications and wide- 5348 Topanga Canyon Blvd.
size telescopes. F. Holden, spread use of computer information networks
Woodland Hills, CA 91364
of Lowell Observatory, could easily lead to many similar fiascos.” Mon-Sat: 9am-6pm (PST)
reports . . . he could see Brian G. Marsden’s worry came true many Toll Free: (888) 427-8766
Sirius B faintly but steadily with a 6-inch aperture times in his long career at the telegram bureau.
Local: (818) 347-2270
Fax: (818) 992-4486
stop on the 24-inch Clark refractor, at 330×. He died in 2010.
 News Notes To get astronomy news as it breaks,
visit skypub.com/newsblog.

LUNAR I Gravity Probes “See” Moon’s Interior

micron per second — “one twenty-thou-
sandth the velocity that a snail moves,” says
principal investigator Maria Zuber (MIT).
Three immediate findings:
• The upper lunar crust is full of gaps
and spaces, like a rock pile. On average
Hertzsprung this pulverized outer layer (excluding the
maria) has a porosity of 12%. The porosity
NASA / GSFC / SCIENCE VISUALIZATION STUDIO

is even greater (up to 20%) around fresher

Orientale
mega-impacts, such as the farside’s Orien-
South Pole-
tale and Moscoviense basins.
Aitken
• The Moon’s crust is only two-thirds
as thick as post-Apollo measurements
pegged it to be: about 27 miles (43 km)
thick at most, and far less in many spots.
Free-air gravity map Bouguer gravity map This thinner skin implies a composition
Gravitational field deviations caused by both the Moon’s bumpy surface and its lumpy interior (left) in keeping with a “big splat” lunar origin.
look quite different from a map with topographic effects removed to reveal density variations under- • Narrow veins of solidified magma lie
neath the surface (right). These views show the lunar farside, centered on 120° west. buried all over the globe. To explain these
veins, the lunar interior must have started
NASA’s twin Gravity Recovery And Launched in September 2011, GRAIL out cooler than the exterior, then later
Interior Laboratory (GRAIL) spacecraft mapped in detail the Moon’s gravity field heated after the crust solidified. This
have revealed unexpected details about by measuring tiny changes in the gravita- outside-in heating scenario would have
the Moon’s interior, scientists announced tional attraction the Moon exerted on the occurred if the Moon built itself up from
December 5th at the American Geophysical two spacecraft as they orbited. The craft collisional debris.
Union meeting. The lunar crust has been measured their separation five times per NASA crashed GRAIL into the Moon in
pulverized so violently that it’s a jumble of second to extreme precision, detecting December after the fuel supply ran out.
rubble at least to a few miles down. orbital velocity changes as small as 0.05 ■ J. KELLY BEATTY

IRON PLANET I Mercury’s Polar Ice Confirmed

NASA’s Messenger mission has finally ice indirectly by counting the neutrons
confirmed that water ice hides in perma- reaching it from Mercury. These neutrons
Kandinsky
nently shadowed craters near the poles are released when high-energy cosmic rays
of blazing Mercury, scientists reported strike the planet’s surface. Hydrogen atoms
Prokofiev
online November 29th in Science. gobble up slow-moving neutrons, so a
In 1991, astronomers mapping Mercury drop-off in the neutrons over certain areas
with radar echoes first detected some- implied plentiful hydrogen — presumably Superposed on images of Mercury’s north pole,
thing that lit up the planet’s north pole in H2O — near the planet’s surface. radar data (yellow) reveal areas of high reflectivity.
like a beacon (S&T: January 1992, page 35). Second, laser pulses from the craft’s All large deposits sit on the floors of craters.
NASA / JHU APL / CARNEGIE INST. OF WASHINGTON
Water ice was the most likely compound to altimeter revealed bright bits of surface that
create such a strong echo. Over the years, match water ice’s reflectivity. Third, ther- Laboratory) says the layer of ice is at least
support for this notion of snowballs in hell mal modeling shows that the floors and 20 inches (50 cm) deep. All told, Mercury’s
grew stronger (S&T: April 2012, page 26). inner walls of many shadowed polar craters polar regions might hold 100 billion to a
Messenger finally gave scientists the never get warmer than –370°F (50 K). trillion tons of ice — somewhere between
tools to prove it using three lines of evi- Team member David Lawrence (Johns a Lake Tahoe and a Lake Erie’s worth.
dence. First, the spacecraft detected water Hopkins University Applied Physics ■ J. KELLY BEATTY

10 March 2013 sky & telescope

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 News Notes

IN BRIEF GALAXIES I Hubble Finds Faraway Galaxies

NASA’s recently launched Van Allen
Probes, formerly known as the Radiation
Belt Space Probes (December issue, page 11.9
8.8
12), have detected dramatic changes in
the Van Allen belts around Earth despite a
relatively quiet Sun, scientists announced
at the American Geophysical Union. As

NASA / ESA / RICHARD ELLIS (CALTECH) AND UDF 2012 TEAM

8.6
part of their two-year mission, the probes
are mapping the altitudes above Earth’s
atmosphere where energetic particles
fly and how these particles are acceler-
ated. Surprising variations have shown
up in the height of the outer Van Allen
electron belt. These changes could affect 9.5
8.8
GPS satellites, which spend considerable 9.5
8.6
amounts of time in that environment. The
mission aims to decipher the connection
between the solar wind and belt activity. Hiding in this Hubble Ultra Deep Field image are seven galaxies seen as they appeared only a
■ MONICA YOUNG few hundred million years after the Big Bang. The numbers refer to the estimated redshifts.

NASA has announced plans for an Astronomers have used the Hubble Space lion years after the Big Bang) to 9.5 (520
extended Mars program, including a sec- Telescope to take a census of the universe’s million years). One outlier is potentially at
ond science rover modeled after Curiosity. first galaxies. The results, reported in the redshift 11.9. That source, UDF j-39546284,
The program also includes supporting the Astrophysical Journal Letters, confirm that was first reported at redshift 10.3 in 2009
currently active Curiosity and Opportunity galaxies started forming gradually in the using HUDF photometry. But the new 11.9
rovers, a 2013 launch for the atmosphere- early universe and not in a dramatic spurt. measurement, which would put the galaxy
studying MAVEN orbiter, the interior- The team used four near-infrared filters 380 million years after the Big Bang, is not
exploring Insight mission slated for 2016 on Hubble’s Wide Field Camera 3 to search airtight. The astronomers only detected the
(December issue, page 16), and participa- for star-forming galaxies about 400 to 600 galaxy in one filter, and there’s a chance
tion in the European Space Agency’s 2016 million years after the Big Bang. The scope that it’s some exotic foreground source,
and 2018 ExoMars missions. The new stared for 100 hours at a square of sky in says study leader Richard Ellis (Caltech).
rover would launch in 2020, its mission Fornax about one-tenth the diameter of the He says that the ultimate test will be a
as-yet undetermined. These plans assume Moon, known as the Hubble Ultra Deep true infrared spectrum, which he hopes to
no budget hiccups. Field (HUDF). The team then combined obtain using one of the Keck telescopes.
■ CAMILLE M. CARLISLE these observations with 2009 HUDF work The census provides a crucial look
to produce the new results. deep into the reionization era. During
Even little failed stars can form planets, Cosmic expansion shifts distant this epoch, ultraviolet radiation from the
a study in the December 20th Astrophysi- galaxies’ light to longer wavelengths, and first post-Big-Bang light sources knocked
cal Journal Letters suggests. Using part highly redshifted galaxies are visible only electrons from the neutral hydrogen atoms
of the growing Atacama Large Millimeter/ at infrared wavelengths. Judging by the filling space. These sources started the
submillimeter Array, Luca Ricci (Caltech) galaxies’ visibility with different Hubble synthesis of heavy elements. The new
filters, the astronomers calculated the study is basically “the deepest archaeologi-
and his colleagues observed the brown
galaxies’ photometric redshifts — estimates cal dig that we have” into this part of cos-
dwarf Rho Ophiuchi 102, which hosts
of how much space has expanded since the mic history, says Abraham Loeb (Harvard-
a thin dusty disk of gas. Rho Oph 102’s
galaxies shone as we see them. Smithsonian Center for Astrophysics).
small mass, 60 Jupiters, had suggested
Photometric redshifts are less accurate When compared with lower redshift
that its disk would be too puny to form
than spectroscopic ones, which measure studies, the new results show that the num-
planets. But the ALMA study reveals par-
narrow spectral lines. But the broad-brush ber of galaxies grew steadily as the universe
ticles have already grown to millimeter approach requires less exposure time. aged. If the transition was smooth, reion-
size, meaning grains might one day stick Using this method, the team found ization was probably gradual, extending
together enough to make rocky planets. seven galaxies that fit the target time range. over several hundred million years.
■ JOHN BOCHANSKI The redshifts range from 8.6 (590 mil- ■ CAMILLE M. CARLISLE

12 March 2013 sky & telescope

 Lagoon Nebula Region in HĮ
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 News Notes

MISSIONS I Voyager’s On-ramp to Interstellar Space

After 35 years in space, NASA’s long-dis- like a plasma swamp. But midway through Mission scientists think the helio-
tance interplanetary probe Voyager 1 finds 2012, Voyager 1’s instruments detected a spheric and interstellar magnetic fields
itself on the cusp of leaving the Sun’s precipitous drop in the number of solar- have somehow become linked, allowing
magnetic bubble. wind particles recorded per second. It charged particles to flow freely inward
After their grand tours of the outer simultaneously noted a surge in cosmic and outward. The link is kind of like a
planets in the 1970s and ’80s, Voyagers 1 rays arriving from interstellar space. This “magnetic highway” to and from interstel-
and 2 headed outward. Mission scientists two-way flow soon became the new normal. lar space.
dreamed that one or both probes would “Things have changed dramatically,” Stone thinks this unexpected zone
keep working long enough to report when says Stamatios Krimigis (Johns Hopkins will prove narrow and that Voyager 1 will
they crossed the outer limit of the helio- University Applied Physics Laboratory), punch through it in a few months to a
sphere, the Sun’s magnetospheric bubble, principal investigator for Voyager’s Low- couple of years. He expects the spacecraft
and entered true interstellar space. But Energy Charged Particle (LECP) instru- to still be operating when that happens.
no one knew how large the heliosphere ment. “The [solar-wind] particles are a Four instruments are still taking data, and
would be. thousand times less than what we had the remaining handful of mission engi-
Now more than 120 astronomical units before. We can hardly measure them.” neers at NASA’s Jet Propulsion laboratory
from the Sun, Voyager 1 is still inside the Ordinarily, scientists would read this figures there will be enough electricity to
heliosphere — but apparently not for long. sudden shift as a clear signal that the run them until about 2020.
Project scientist Edward Stone (Caltech) craft had entered the domain of interstel- About 100 a.u. from the Sun, Voyager
and his colleagues announced December lar space. But although the surrounding 2 has seen similar changes in its mag-
3rd that Voyager 1 has entered a new and magnetic field intensified dramatically, its netospheric environment, but nothing
unexpected zone that puts it on the door- orientation remained rock-steady, aligned like those experienced by its more distant
step of interstellar space. east-west roughly along the ecliptic. (In twin. The second probe appears to have
Since late 2004 Voyager 1 has been contrast, scientists expect the orienta- some distance yet to go before reaching
immersed in a stagnant region of slow- tion of the interstellar field to be roughly this on-ramp to interstellar space.
moving solar-wind particles, something north-south.) ■ J. KELLY BEATTY

IN BRIEF eye on events in the universe, the way observ-

ing new wavelengths beyond visible light did
principle, this five-fold deuterium enrichment
can be used to figure out just much water the
Scientists might be closer than they thought during the 20th century. Red Planet has lost.
to directly detecting gravitational waves in ■ CAMILLE M. CARLISLE ■ J. KELLY BEATTY
spacetime, a key prediction of Einstein’s the-
ory of gravity. Weak gravitational-wave ripples NASA’s Curiosity rover has detected water Simulations by an American and Finnish
should be created by any accelerating mass. vapor and simple organic molecules in sam- team suggest that widely separated binary
Astronomers have only indirect evidence of ples of Martian sand, scientists announced stars formed not as twins but as triplets. Most
their existence so far, because it takes a large, at the December 3rd American Geophysical binaries are tight enough that they could have
dense mass accelerating rapidly to make Union meeting. The organic molecules are formed in the same interstellar cloud core,
strong gravitational waves. But new work sug- almost certainly byproducts of the testing but some are far too wide for that. Reported
gests they’re on the horizon. Sean McWilliams process, created when the rover’s tiny ovens December 13th in Nature, the new simula-
(Princeton) and his colleagues and Alberto released different compounds from heated tions followed the evolution of newborn triple
Sesana (Max Planck Institute for Gravitational grains. But the water vapor is natural to Mars systems. More than 90% of systems were
Physics, Germany) suggest that careful tim- and shows five times as much deuterium disrupted; those that survived as triplets
ings of pulsar blips from all around the sky — to hydrogen as Earth’s seawater. That’s as ended up with two stars closely orbiting each
nature’s most precise clocks — could reveal expected: scientists think that, over the eons, other and the third flung to a far distance, like
errant beats caused by spacetime ripples in ultraviolet sunlight has steadily broken down the red dwarf Proxima Centauri that drifts
the next few years. McWilliams’ team con- water molecules at the top of Mars’s atmo- far from the Alpha Centauri AB pair. From far
cludes that such signals might even be detect- sphere, and the lighter hydrogen atoms pref- away, some of these systems would look like
able in current data. If measured well enough, erentially escaped to space while the heavier wide binaries, the authors suggest. ✦
gravitational waves could open a whole new deuterium atoms more often stayed put. In ■ CAMILLE M. CARLISLE

14 March 2013 sky & telescope

 Volunteer for Dark Skies
The U.S. National Park Service is seeking volunteers with
amateur astronomy and outreach experience
to help share and protect dark night skies
Commitments of 4 weeks are preferred in one of
several parks around the country

Teresa_Jiles@partner.nps.gov
www.nature.nps.gov/night/volunteer.cfm

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Sk yandTelescope.com March 2013 15

In Memoriam
Timothy A. Lyster

Alas, No Moore
Patrick Moore was the face of astronomy for
many in Britain — and around the world.

Sir Patrick Moore died December 9th at his

home in southern England; he was 89. Best known as the
colorful host of the BBC’s The Sky at Night, the longest-
running program in television history with the same
presenter, he missed just one of the show’s 721 monthly
episodes (having been hospitalized with a near-fatal dose
of food poisoning in July 2004). Moore was the instantly
recognizable face of amateur astronomy for millions of
Britons, the quintessentially eccentric Englishman — and
mad scientist — with machine-gun delivery, bushy eye-
brows, outsized suits, and his trademark monocle lodged
firmly over his right eye.
Patrick Alfred Caldwell-Moore was born March 4, 1923,
in Middlesex, England. His interest piqued as a child, he
used a newly acquired 3-inch Broadhurst Clarkson refrac-
tor to observe the Moon and published his first scientific

S&T PHOTO ARCHIVE

paper, “Small Craterlets in the Mare Crisium,” at age 13,
in the Journal of the British Astronomical Association. Thus
began a lifelong fascination with Earth’s satellite.
After serving as a navigator in Bomber Command
during World War II, Moore returned to civilian life to was the greatest popularizer of science that ever lived.”
teach and resume his observations of the night sky. From Another longtime friend, Terry Moseley, former
his home observatory, he mapped lunar features through President of the Irish Astronomical Association, recalled
a 12½-inch reflector, and his resulting descriptions were the time when Moore was the director of the Armagh
used by NASA and the Soviet Union during the early Planetarium in Northern Ireland from 1965–68. “He trod
years of the space race. his own path and really enjoyed a good astronomical —
Following his appearance in a televised debate about and at times, political — debate.”
UFOs, he was asked to host three pilot episodes of The Despite being an almost universally beloved figure,
Sky at Night in 1957. Over the next 55 years, Moore’s Moore could occasionally court controversy, as when he
unique personality and natural ability to communicate referred to immigrants as “parasites,” and stated that the
complex subjects in layman’s terms kindled the interest of BBC was being “ruined by women.” As he said of himself:
countless numbers of future astronomers, and turned his “I may be accused of being a dinosaur, but I would remind
show into a cult hit. As presenter, he was witness to the you that dinosaurs ruled the Earth for a very long time.”
chief astronomical events of the era, from the first man in Of his many contributions to the field, the Caldwell
space to Curiosity on Mars, and he interviewed many of Catalog may be familiar to many readers (S&T: December
the leading lights of astronomy and space exploration. 1995, page 38), a collection of 109 deep-sky objects that
John Mason, past president of the British Astronomical Moore assembled as an adjunct to Messier’s list. It now
Association, knew Moore for 44 years and often accompa- stands as a fitting tribute to a man who spent his life
nied him on trips. “He was the most incredible company, bringing the wonders of the night sky to the public. ✦
with a wicked sense of humor,” he said. “Patrick made
astronomy accessible. Millions around the world picked Former S&T managing editor Timothy A. Lyster worked with
up a book by him that sparked their interest. I believe he Patrick Moore on the British periodical Astronomy Now.

16 March 2013 sky & telescope

Backyard Astronomers: Get Ready for

COMET PANSTARRS

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Comet Photo Credit: Sebastian Voltmer

 Universal Records

Cosmic
Extremes
The universe is faster,
colder, and wackier
than anything we can
possibly comprehend.

18 March 2013 sky & telescope

 Bryan Gaensler
The universe extends far beyond our everyday experience in
every imaginable way. But at the same time, it’s truly remark-
able that we can actually measure some of the universe’s
properties. What’s more, we think we understand what most
of these objects are, how they formed, and why they have their
incredible characteristics.
Below I run through some of the concepts we experience on
a daily basis: speed, temperature, gravity, density, and size.
For each example there are extremes in our own experience:
we all feel blazing heat and bitter cold, we see a jet plane speed
overhead, and we watch a snail creep through a garden. But
what are the absolute extremes that the cosmos can offer?

Fastest Spinning Star

Neutron stars are generally born spinning 30 to 50 times per
second. But powerful magnetic fields gradually brake their
rotation speeds as they age. Millions of years after its birth, a
neutron star might spin only once every 5 to 10 seconds. This
is still ridiculously rapid compared to most stars and planets,
but it’s glacially slow for a neutron star.
Bizarrely, some neutron stars can reverse their gradual
spin-down. Despite now being hundreds of millions or even
billions of years old, these stars spin more rapidly than at any
previous point in their lives. The current record holder is a
neutron star in Sagittarius named PSR J1748–2446ad, which
is spinning 716 times per second! And what’s more, this and
dozens of other rapid rotators are not only spinning unusu-
ally fast, they are barely slowing down at all. A billion years
from now, PSR J1748 will probably still be spinning more
than 500 times per second — faster than a kitchen blender.
Such neutron stars were originally in a binary system
with a normal star. If the orbit is sufficiently small, the neu-
tron star’s extreme gravity will strip gas off its companion’s
surface and drag it down toward its own surface. As this gas
swirls downward to the neutron star and impacts its sur-
face, it gradually adds its angular momentum, making the
neutron star spin faster and faster. Given enough time, it can
reach rotation rates of hundreds of times per second.

WHIRLING DERVISH This illustration depicts a pulsar that is

siphoning material from a companion star. The gas forms a disk
around the pulsar and eventually spirals in, gradually spinning up its
rotation rate. A pulsar named PSR J1748–2446ad is the fastest-spin-
ning star known; it rotates an incredible 716 times per second, near
the theoretical maximum rate it can spin without breaking apart.

Reprinted from Extreme Cosmos by Bryan Gaensler, Ph.D., by

arrangement with Perigee, a member of Penguin Group (USA) Inc.
NASA

Copyright (c) 2011 by Bryan Gaensler.

Sk yandTelescope.com March 2013 19

 Universal Records

SHAMI CHATTERJEE / JAMES CORDES (CORNELL UNIVERSITY) / PALOMAR OBSERVATORY

Fastest Known Star:

Neutron stars also hold the record for the fastest-
moving stars. If a supernova explosion were per-
fectly spherical and symmetric, debris would shoot
out evenly in all directions, and the newly produced
neutron star would sit stationary at the center.
But for reasons that we’re still struggling to
understand, these detonations are often asymmet-
ric — material is blasted outward in some direc-
tions faster than others. Even if the asymmetries
are minor, the explosion’s energy is so large that
if material is blasted away at higher speed in one
direction, it can kick the newborn neutron star in
the opposite direction at an extreme speed
The fastest known neutron star, and indeed the
fastest known star of any kind, is PSR B2224+65,
an estimated 6,000 light-years away in Cepheus.
PSR B2224+65 rotates at the comparatively sedate
rate of 1.5 times per second. But what it lacks in
spin it makes up for in sheer speed. If the distance Fastest Known Object Other Than Light:
estimate is accurate, the pulsar is racing through Trillions of cosmic rays crash into Earth every second. Cosmic rays
space at an incredible 3.6 million miles per hour. are not actually “rays” per se; they are subatomic particles and atomic
This is 4,700 times the speed of sound in Earth’s nuclei that typically travel at around 99% of the speed of light. This is
atmosphere, 50 times faster than Earth’s orbital faster than almost anything else in the universe, but it’s still almost 7
speed around the Sun, and about twice as fast as million miles (11 million kilometers) per hour slower than light itself.
the recently discovered population of hypervelocity But a tiny fraction of cosmic rays makes 99% of light-speed seem
stars that have been ejected from the Milky Way downright sluggish. This rare population of ultrahigh-energy cosmic
by a close encounter with the central supermassive rays approaches the fastest speeds possible under the laws of physics.
black hole. PSR B2224+65 travels the distance from The definitive record for the fastest speed ever measured in the
New York to Los Angeles every 2.5 seconds, and the universe, except for light itself, was set at 1:34:16 a.m. local time on
Earth-Moon distance every 4 minutes. Tuesday, October 15, 1991, at the High Resolution Fly’s Eye Cosmic
Ray Detector near Dugway, Utah. A cosmic ray slammed into Earth’s
GUITAR NEBULA Top of page: The pulsar PSR B2224+65
races through space at an estimated 3.6 million miles per atmosphere, detonating into a spectacular shower of secondary par-
hour, making it the fastest known star. As it plows through ticles. Using the pattern and extent of this debris, scientists recon-
interstellar gas, it produces a bow-shock nebula resembling structed the speed at which this proton or atomic nucleus must have
a guitar. This image was taken through a hydrogen-alpha
filter by the 200-inch Hale Telescope on Palomar Mountain.

20 March 2013 sky & telescope

BLAZING SPEED An artist depicts a cosmic ray shower. A high-speed Largest Object:
particle or atomic nucleus smashes into Earth’s upper atmosphere at The largest known struc-
near-light speed and disintegrates, but not before its kinetic energy trig- ture in the universe is
gers a cascade of secondary particles that reach the surface. By using a colossal filament of
particle detectors to measure the debris, scientists can reconstruct the thousands of galaxies
energy (and thus the speed) of the original particle. A cosmic ray that hit
known as the Sloan Great
the atmosphere over Utah on October 15, 1991, was traveling so fast that it
Wall, discovered in 2003.
carried the energy of a baseball thrown at 60 miles per hour.
The Sloan Great Wall is
approximately 1.4 billion
light-years across, and runs
behind the constellations
of Hydra, Sextans, Leo, and
Virgo, stretching across
almost a quarter of the
sky. It’s not a single linear
thread; instead, it writhes Sloan Great Wall
and twists, even split-
ting up into two separate
tendrils for a few hundred
million light-years, which
then rejoin farther along.
THE 2DF GALAXY REDSHIFT SURVEY TEAM

ASPERA / NOVAPIX / L. BRET

hit our planet, and the result was astonishing: it was moving at
99.9999999999999999999996% of the speed of light! Put another
way, suppose this particle raced a light ray over a length of a mil- Fastest Orbiting Planet:
lion light-years. The light ray would beat the proton to the finish
The record for the fastest known orbital motion
line by only about 1.5 inches (4 cm). Talk about a photo finish! of any planet goes to HD 80606b. A few times
The cosmic ray seen in October 1991 earned its own moniker: more massive than Jupiter, HD 80606b traces
the “Oh-My-God Particle.” This particle’s energy was staggering: out a highly elongated, cometary-style orbit,
more than 12 calories of energy when it arrived at Earth. To put completing its path around its parent star every
this in perspective, consider the Large Hadron Collider (LHC) — 16 weeks. For part of its orbit, HD 80606b moves
the most powerful particle accelerator ever constructed. The LHC relatively slowly, and sits about as far from its
can boost subatomic particles up to a maximum energy of only star as Venus does from the Sun. But for a brief
around 0.0000002 calorie. Some unknown natural process in the interval in every orbit, it swings inward, ventur-
cosmos can accelerate a tiny particle to an energy 50 million times ing 13 times closer to its star than Mercury’s
greater than we humans can achieve. Such particles carry the distance from the Sun. At closest passage, HD
S&T: LEAH TISCIONE

same energy as a baseball thrown at 60 miles per hour. 80606b hits a top speed of 529,000 miles per
hour, or almost 150 miles every second.

Sk yandTelescope.com March 2013 21

 Universal Records

Deepest Known Note:

The deepest note in space yet identified belongs to the galaxy thus which note is playing. Fabian and his colleagues reached the
cluster Abell 426, often nicknamed the Perseus Cluster conclusion that Abell 426 is humming in B flat.
because of its location in that constellation. Abell 426 is about But this B flat is unlike any note you’ve heard. The sound
250 million light-years away. waves have an oscillation rate of once every 9 million years, which
Although we can never directly hear Abell 426’s tune, we is 57 octaves below the B flat that’s above middle C, or about
can see the pressure waves it generates. The gas that perme- 6,000 trillion times deeper than the lowest note that the human
ates the cluster, is incredibly hot, with a temperature exceeding ear can hear. You would need to add another 635 keys to the left
50,000,000°°F. At this extreme heat, this gas becomes incandes- end of a piano keyboard to play a note this low!
cent, and radiates extremely energetic and copious X rays.
In 2002 Andrew Fabian (University of Cambridge, U.K.)
used NASA’s Chandra X-ray Observatory to make a detailed
image of the X-rays produced by Abell 426’s hot gas. These
observations surprisingly revealed a series of concentric
ripples like those we see around a stone thrown into a pond.
Fabian and his colleagues showed that these ripples corre-
spond to places in the cluster where the gas density is slightly
higher than the average. In the gaps between the ripples,
they found that the gas density is slightly lower than average.
Since a higher density means a higher pressure (and a lower
density means a lower pressure), these ripples are oscillations
in pressure, a giant sound wave that thrums throughout this
vast cluster.
The origin of this racket is a supermassive black hole at
the cluster’s center. This black hole blasts out two oppositely
directed high-speed jets of material that travel outward over
millions of light-years at nearly the speed of light. These twin

S
NASA / CXC / M. WEIS
jets must force their way through the cluster’s hot gas. Like a
garden hose running underwater, the jets’ collision with the
cluster’s gas generates a series of bubbles that inflate under
the jets’ power, and then break off and drift outward. As these
bubbles expand, they shove the surrounding gas outward, set-
AN ULTRADEEP B FLAT The main image, from NASA’s Chandra X-ray
ting up the pressure oscillations that ring through the cluster.
Observatory, shows how a giant black hole in galaxy NGC 1275 is affect-
Determining the pitch of the corresponding note is rela- ing the entire galaxy cluster Abell 426. The black hole shoots out two
tively easy. The speed of sound in this 50,000,000°F gas is powerful jets (not seen in this picture), which blow through the hot, X-ray-
about 2.6 million miles per hour, and the spacing between emitting intergalactic gas, creating bubbles that push aside surrounding
each ripple is about 36,000 light-years. We simply need to gas. This energetic interaction generates sound waves that oscillate
divide the speed of the wave by the spacing of the ripples to through the cluster and create ripples (inset). In musical terms, the spac-
determine the rate at which the pressure wave oscillates, and ing of the ripples is a B flat 57 octaves below the B flat above middle C.

NASA / CXC / IOA / J. SANDERS, ET AL.

Strongest Electrical Current: NASA / ESA / S. BAUM / C. O’DEA / R. PERLEY / W. COTTON /

Abell 426’s jets produce the gas vibrations associ-

ated with a deep note. But the jets from many other
HUBBLE HERITAGE TEAM (STSCI / AURA), ET AL

supermassive black holes travel unimpeded for a

million light-years. Full of charged particles flying
outward at high speeds, these jets carry the highest
observed currents in the universe, typically at the
level of 1 million trillion amps. Their power output is
so large that in a single millisecond, one of these jets
could provide enough electricity to cover humanity’s Hercules A
energy needs for the next 20 trillion years.

22 March 2013 sky & telescope

Lowest Density
For centuries, laboratory scientists found clever ways
to push to increasingly lower densities, creating ever
more rarefied environments. The current state of the art,
involving experiments that take several months, results in
a gas density of just 500 to 1,000 atoms per cubic centi-
meter. By all reasonable measures, a gas in this state is
a near-perfect vacuum. But the universe can effortlessly
deliver far lower densities than this.
Galaxies are not scattered uniformly throughout the
universe, but are arranged into a spectacular web of
sheets, filaments, and shells. The walls of these inter-
galactic soap bubbles are busy agglomerations of stars

NASA / ESA / HUBBLE HERITAGE TEAM (STSCI / AURA) / JOHN BIRETTA

and galaxies. But the bubble interiors are unimaginably,
frighteningly empty. In these vast wastelands, often
stretching across space for more than 100 million light-
years, there is often nothing more than the occasional
lone atom of hydrogen.
The density of a typical void is an incredibly desolate
0.00000002 atom per cubic centimeter. This is so sparse COSMIC FREEZER Several Hubble Space Telescope visible-light
that even in a volume the size of a large room, you would images taken through polarization filters were combined to produce
be lucky to find a single atom. Put another way, if you this false-color image of the Boomerang Nebula. The central star is
were to grind a bowling ball into its individual constituent casting off its outer layers, which expand and cool to just 2°F (1°C)
above absolute zero. Each lobe is about a light-year long.
atoms, you would have to spread them over a volume 4 mil-
lion miles across to achieve the same density as in a cosmic
void. The massive surveys of the universe that astronomers
have undertaken over the last 20 years have now revealed Coldest Known Place
that these voids occupy around 90% of the volume of the The coldest temperature allowed by the laws of physics is abso-
universe, with everything else in the margins. lute zero, at –459.67°°F (–273.15°C). Laboratory experiments have
reached temperatures within a billionth of a degree of absolute
zero, but to reach these unbelievably frigid depths requires compli-
cated and expensive equipment. The natural universe has no such
equipment at its disposal, so how cold can it get?
The usual answer is the cosmic microwave background (CMB),
the afterglow radiation from the Big Bang. The CMB has a tem-
perature of –454.76°F, just 2.73°C above absolute zero, so it heats
up space to a few degrees above the minimum possible tempera-
ture. But the Boomerang Nebula is even colder.
The Boomerang is a protoplanetary nebula, the result of layers
of gas being shed by a star nearing the end of its life. The dying
star that created this nebula had an extremely strong wind. For
the last 1,500 years of its life, the star has been blasting this wind
material into space at almost 370,000 miles (590,000 km) per hour.
The star sheds about 70,000,000,000,000,000 tons of material
through this wind every second. Besides its high speed, the stellar
wind also expands rapidly as it flows outward. This rapid expan-
sion causes a dramatic drop in temperature — essentially the
SLOAN DIGITAL SKY SURVEY COLLABORATION

reverse of the effect you experience when your bicycle pump heats
up as you squeeze air into a tire.
AVOID THE VOIDS Maps of cosmic large-scale struc-
The result is that the Boomerang Nebula’s gas is at a bone-chill-
ture, such as these slices from the Sloan Digital Sky Survey, ing –457.8°F (–272.1°C), even colder than the CMB. Although the
reveal that matter is clumped in sheets and filaments that central star powering the Boomerang Nebula is very hot, the combi-
surround vast regions (dark areas) of virtually empty space. nation of a high-speed wind and rapid expansion has produced the
Such voids have only an occasional atom per cubic meter. coldest natural place we know of in the universe, with a tempera-
ture even lower than the extreme chill of the surrounding space.

Sk yandTelescope.com March 2013 23

 Universal Records

Weakest Gravity:
Black holes exert powerful gravitational forces,
but what lies at the other end of the spectrum?
How weak can gravity get? Or to rephrase the
question more carefully, what is the gentlest pull
that any object in the universe exerts, and yet is
still able to force another body to orbit it?
Many small galaxies have correspondingly
weak gravity. But if two low-mass galaxies can
somehow come together in an isolated region
of space such that they can move without being
affected by larger galaxies, they can reach out
with their feeble gravity and take up a fragile
orbit around each other.
Of the many binary pairs of small galaxies
we know of, the pair that is bound together
most weakly is an obscure duo known as
SDSS J113342.7+482004.9 and SDSS
J113403.9+482837.4, or as I like to call them,
Napoleon and Josephine. These two galaxies
are 139 million light-years from Earth in Ursa
Major. Napoleon and Josephine are 40,000 times
too faint to see with the naked eye and, even
through a telescope, they make a rather unim-
pressive couple. Each galaxy is about a thousand
times less massive than the Milky Way, and both
appear as unremarkable smudges in deep astro-
nomical images.
But what’s surprising about these two galaxies
is the weakness of the gravity with which they
hold each other together in their orbit. The larger
of the two, Napoleon, reaches across 370,000

SLOAN DIGITAL SKY SURVEY COLLABORATION

light-years to its companion with a gravitational HEADING FOR DIVORCE The two circled gal-
attraction 900 trillion times lower than an apple axies that the author has nicknamed Josephine
(top) and Napoleon appear as faint smudges in
experiences when it falls from a tree. If you hov-
this Sloan Digital Sky Survey image. The galaxies
ered at the position of Napoleon and dropped an
are just barely bound to each other gravitation-
apple toward Josephine, you would have to watch ally. Other points of light in this field are either
the apple for 50,000 years for it to accelerate up foreground stars or background galaxies.
to a speed of about an inch per second, slightly
faster than a garden snail. Wait another 4 million
years or so, and it would move up to around walk-
ing speed. Extreme Cosmos
Not surprisingly, with this incredibly weak The numbers that measure cosmic extremities can at first seem difficult to
gravity between them, these galaxies take an comprehend. But on closer inspection, the universe’s extremes become not
eternity to orbit around each other. In fact, in the only comprehensible, but turn out to be the vital keys needed to unlock the
billions of years since these two galaxies formed, true wonder and elegance of the heavens. Despite the seemingly hopeless mis-
they have probably passed through barely one- match between our limited human imaginations and the size and complexity
fifth of their first orbit. And it’s unlikely they will of the universe, it’s astonishing that we understand so much of what we see.
ever complete that orbit. The gravitational attrac- As baffled and cowed as we often find ourselves when confronted by the cos-
tion between Napoleon and Josephine is so weak mos, it’s perhaps humanity’s ultimate accomplishment that we nevertheless
that it’s merely a matter of time before some can explain and appreciate the grandeur we observe in the night sky. ✦
wandering galaxy interloper passes through their
neighborhood and uses its stronger gravity either Bryan Gaensler is an Australian Laureate Fellow at the University of Sydney and
to capture these two into its own orbit, or to scat- is the Director of the Australian Research Council Centre of Excellence for All-sky
ter this delicate pairing to the winds. Astrophysics. Follow him on Twitter at @SciBry.

24 March 2013 sky & telescope

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 Titan’s Soggy Enigma

Where Goes
the Rain?
Donald F. Robertson

It is raining. A stream emerges from a wide If it does rain methane on Titan, the compound must
canyon cut through low hills. It meanders across a fine- return to the sky through evaporation so that it can fall
grained beach and runs gently down to a calm sea. as new rain. Scientists have had a hard time finding that
At first glance, the scene looks remarkably like Earth. return path and closing Titan’s weather cycle. But recent
Look closer, though, and this rain is fantastically strange. studies have uncovered strong evidence of evaporation —
The raindrops are half again the size of drops on our and potentially from an unexpected source.
planet. They fall with dreamlike slowness in the low grav-
ity beneath a hazy, orange sky. This rain is not made of Mysterious Methane
water: it’s methane (CH4). Scientists think Titan’s rain is methane because this com-
This vision of Saturn’s giant moon Titan is not pure pound is both abundant in the atmosphere (it accounts
fiction. Since the paired NASA Cassini spacecraft and ESA for 5% of the atmosphere at the surface, around the same
Huygens probe first arrived in the system in 2004 (S&T: amount as water vapor on Earth) and exists on Titan near
January 2005, page 20), scientists have discovered indirect its triple point. A triple point is the combination of pres-
but strong evidence for rain on Titan. Cassini has observed sure and temperature that allows a compound to be stable
temporary discoloration of desert sands in the wake of as a solid, liquid, or gas. On Earth, conditions match
cumulus clouds, and radar images show canyons and den- water’s triple point, and water’s rapid dance between
dritic channels, which imply drainage from precipitation. states, absorbing and releasing solar energy at every step,
Some of these channels may be active riverbeds empty- drives the immense complexity of our weather.
ing into dark areas near the poles. These areas can be the In addition to methane, Titan has a second climate
size of North American Great Lakes. Specular reflections actor: ethane (C2H6), which is produced when methane
— like sparkles on a lake at sunset — and other evidence interacts with sunlight. Ethane is not quite at its triple
imply that the dark features are liquid-filled seas. If so, point, but it’s not so far off that it lies frozen as an inactive
they are mirror-flat. The moon’s weak surface winds are solid. Cassini observations have identified ethane as one
typically predicted to blow below the threshold necessary of the principal constituents in the lakes. Like a godfather
to make waves, but they might kick up occasional ones up figure pulling hidden strings behind the scenes, ethane
to a half meter (less than 2 feet) tall during summer, says is probably active just enough to be important in Titan’s
planetary scientist Alex Hayes (Cornell University). long-term climate cycle.
Flat, lake-like features, dendritic channels, river deltas, If all it did was rain on Titan, the clouds and methane
and discolored sands — it all adds up to strong, albeit would soon disappear from the atmosphere. The poles
circumstantial, evidence for rainfall. appear to receive annual rainfall, whereas some equatorial

26 March 2013 sky & telescope

Saturn’s moon Titan has a
mysterious weather cycle.
Illustration by Casey Reed

NASA / JPL-CALTECH /
SPACE SCIENCE INST.
regions might wait 100 or even 1,000 years for a torrential
storm — the morphology of streambeds suggest that
clouds could dump tens of centimeters or even meters
of rain. However rare, these storms and the polar rains
should deplete the atmospheric methane much faster HAZY MOON Larger than the planet Mercury, Titan hides a
than typical geologic processes can restore it. fascinating landscape beneath its orange haze, visible here in a
That brings up a second issue, one acting on a far lon- natural-color composite from NASA’s Cassini spacecraft.
ger timescale. Methane is unstable over geologic times,
because solar radiation destroys atmospheric methane. remain unclear, says Hayes. If the removal of liquid is to
Calculations suggest the moon must generate some 50 blame, the hydrocarbons could have either seeped into the
million tons of methane each year just to keep its atmo- ground or directly evaporated into the atmosphere. Last
sphere enriched to present-day levels. There must be year, researchers discovered potential oases or mudflats
some source of methane seeping out of Titan itself, but it near the desert-like equator, patches of sand that might
remains unclear what that source is. be dampened by liquid only a few inches deep welling up
Although scientists still don’t have the answer to the from the ground (October issue, page 12). Careful study of
geologic side of Titan’s methane mystery, they’re much Ontario Lacus, a large lake near the south pole, also sug-
closer to understanding methane on the seasonal time- gests it might be a depression that drains and fi lls from
scales relevant to weather. below, implying some sort of “groundwater” (in this case,
ground methane).
Alien Fog However, the river-like channels indicate that rain does
Titan’s extraordinarily deep atmosphere prevents the Cas- fall and drain into lakes. And even if the lakes primarily
sini orbiter from flying closer to the moon’s surface than fill from a subsurface reservoir instead of the atmosphere,
about 900 kilometers. Because of that great distance and evaporation must still play a role, Hayes explains. “The
the perpetual haze, Cassini’s images have resolutions of methane needs to return to the atmosphere somehow,” he
hundreds of meters (compared with some orbital images says. “The only difference is whether the liquid inter-
of Mars, where we can distinguish person-size objects). acts with the subsurface (either by flowing in a porous
While Cassini has observed changes in south polar medium or by wetting water-ice) before evaporating, or
lakes using both its Imaging Science Subsystem (ISS) evaporates directly from the pooled liquid.”
cameras and its radar — including the disappearance of Earlier in the Cassini mission, Michael Brown
some small lakes — the exact reasons behind the changes (Caltech) and his colleagues found evidence for direct

Sk yandTelescope.com March 2013 27

 Titan’s Soggy Enigma

Surface filter Lower troposphere filter Troposphere filter

FOG RISING Fog-

like features appear
in shots of Titan’s
surface (near right)
and also in the
lower troposphere
(center), but are
not as pronounced
higher up.
MICHAEL E. BROWN ET AL. /
ASTROPHYSICAL JOURNAL

evaporation, in the form of two different kinds of conden- looked for temporary features visible near the surface, but
sation. The first is lake-effect clouds near the large north not visible higher in the atmosphere.
polar seas. Lake-effect clouds form as colder air flows After carefully reviewing some 9,000 images by eye,
over a relatively warm lake, picking up vapor which then the team found four low-lying wisps near Ontario Lacus.
condenses over land. One terrestrial example is the heavy Their spectra were unlike that of any nearby surface, but
snowfall that blows off Lake Michigan and onto residents they were similar to the spectra of methane clouds seen
of Chicago. (But Titan is too warm for methane snow.) higher in the troposphere. The best fit to the data were
The second type of direct evaporation from the surface clouds of vapor just 750 meters above the ground — fog.
is fog. Any fog must lie close to the ground, a long way Finding fog and lake-effect clouds does not explain
from prying orbital eyes. In a clever and elegant experi- how they got there. Fog generally forms when a com-
ment, Brown’s team used an artificial filter to split exist- pound (such as water on Earth) condenses from nearly
ing images from Cassini’s Visible and Infrared Mapping saturated air. The only reasonable explanation for such
Spectrometer (VIMS) into four wavelength ranges. Each high methane humidity on Titan is that the hydrocar-
range penetrated to a different altitude. The scientists bon evaporates from the moon’s surface. Brown and his
colleagues suggested that nearly pure evaporating liquid
methane would be the best explanation for their results:
the fog-like features were made of large particles, such as
those found in methane clouds in the troposphere, mean-
ing they probably formed from the condensation of an
abundant compound. Methane is the only major surface
constituent that could evaporate in the conditions present.
Fog also needs cooled air to persist. Terrestrial fog
forms when air temperatures cool to within a couple of
degrees of the dew point, the temperature at a given pres-
sure where water condenses. Titan’s atmosphere is too
NASA / JPL / UNIVERSITY OF ARIZONA / DLR

dense to cool much on short timescales, even during the

world’s Earth-day-long evenings. But pools of evaporat-
ing liquid methane could drain heat from overlying air,
ALIEN LAKE Cassini caught this flash of sunlight off a
lake’s surface in 2009. This glint, called a specular reflec-
explaining how temperatures could drop to fog-sustaining
tion, confirmed the presence of liquid in the moon’s conditions, the scientists concluded.
northern hemisphere. Although pure methane could evaporate on Titan, the
compound would disappear far too quickly to explain the
seas, which are stable on a seasonal timescale. Ethane
lies at the other end of the scale. Ethane does not eas-
S U B S U RFAC E O C E AN? ily evaporate, and its presence in large concentrations
Deep below Titan’s icy surface could lie a liquid water- actually inhibits the effective evaporation of methane.
ammonia ocean. Analyses of Cassini observations Scientists think that the lakes are primarily ethane with
suggest that an ocean starts somewhere between 50 and a bit of methane mixed in, which would make the lakes
stable long enough to explain their growth in summer
200 km below the crust and is possibly 300 km thick.
and waning in winter. Titan’s year lasts 29½ Earth years,
so that stability has to last several Earth years.

28 March 2013 sky & telescope

 A Foreign Atmosphere
Still, the lakes cover only 20% or less of the polar Saturn’s moon Titan features many Earth-like landscapes: elevated terrains
regions during summer; overall, they make up a few cut by what look like rain-fed streams and river canyons, the largest dune
percent of the moon’s total surface. Whether direct fields discovered in the solar system, and lakes that rival those on Earth.
evaporation from the lakes could close the methane Even the atmosphere is often described as similar to Earth’s.
cycle on its own is an open question. It’s not. Titan’s atmosphere is predominately molecular nitrogen and
supports cumulus clouds in the troposphere, like Earth, but that is where
By Land, Not by Sea any resemblance ends. The second most abundant gas is not the chemically
To understand Titan’s meteorology, “one has to show up hyper-reactive oxygen, or even water vapor, but methane — with the addi-
and observe,” says F. Michael Flasar (NASA Goddard tion of a lot of smog-like complex organic chemicals.
Space Flight Center). On January 14, 2005, researchers Relative to the planet’s size, Earth’s atmosphere is about as thin as an
did just that when the Huygens probe became the first eggshell. Three-quarters of the gas lies within 11 kilometers of the surface,
vessel to make landfall in the outer solar system (S&T: and “space” is defined as beginning at 100 kilometers.
April 2005, page 34). Titan’s atmosphere is deep: the atmosphere extends more than 600 kilo-
Huygens’s equatorial landing site (10.2°°S, 192.4°W) meters, over one-fourth of the moon’s radius. Most of Titan’s rain clouds
looks like a sandy flood plain, just off a rugged highland reside above 10 kilometers, many times higher than on Earth. The mass of
called Adiri. Recent analyses of Huygens’s data show
all that gas on this small world, even in Titan’s low gravity, results in a sur-
that the probe made a 12-centimeter-deep hole when
face pressure 50% higher than Earth’s.
it landed, then bounced out to slide along the moon’s
surface and wobble to a halt. The landing’s dynamics
suggest the probe fell on damp sand covered by a dry 10 –6
dust layer, possibly organic particles that drizzled out Thermosphere Methane destroyed 800
of the atmosphere. The sand, probably made of water by ultraviolet light
ice or organic material like the dunes, supports pebbles 10 –4
600
Pressure (millibars)

that appear rounded in the same way silicate rocks are

Altitude (km)
eroded in streams on Earth. Mesosphere
During the landing, the Gas Chromatograph Mass 10 –2 400
Spectrometer’s warm inlet tube was shoved into the Detached haze
300
sand and saw a sudden increase in methane gas, as well
as other hydrocarbons. Ralph Lorenz (Johns Hopkins 1 Stratosphere 200
Huygens parachute
University Applied Physics Lab) argues the GCMS’s deployed
Main haze 100
inlet appeared to be embedded in a surface that acted as layer
50
an effective heat sink, most plausibly ground that’s wet 100
Troposphere Methane clouds 25
or damp with liquid methane. Erich Karkoschka and
0
Martin Tomasko (both of the University of Arizona’s 80 100 120 140 160 180
Lunar and Planetary Lab) think the probe’s camera Temperature (Kelvin)
might even have seen a methane dewdrop falling from a
cold baffle on the descent imager. 100
The presence of moisture in the sand at the landing 10 –3 Thermosphere
site was the clue scientists needed to look for another
potential source for the fog. There’s no standing 10 –2 80
methane near Huygens’s landfall, but Hayes points out
Pressure (millibars)

10 –1
that lakes cover only a small fraction of Titan’s surface. Mesosphere

Altitude (km)
60
“You have a much larger surface area of potentially wet
ground,” he says. “So, if the liquid is at or very near the 1
surface, the total volume of evaporated methane could
Stratosphere 40
be greater over the sand than over a lake surface with a
similar composition.” 10 Ozone layer
If methane evaporates from the ground, moisture- 20
laden air pulled from the land could pass over lake 100
Troposphere
margins, where it would encounter lower air pressures Water
W
Wa t r clouds
te clou
uds
S&T: GREGG DINDERMAN

and temperatures, says Tetsuya Tokano (University of 0

170 190 230 270 310 350
Temperture (Kelvin)
Descend with Huygens through Titan’s haze and
see more awesome Titan sights at skypub.com/ TWINS? NOT SO MUCH Titan’s atmosphere (top) has similari-
TitanUnveiled. ties to Earth’s (bottom), but notice the altitudes: Titan’s strato-
sphere reaches roughly six times higher than Earth’s does.
 Titan’s Soggy Enigma

NORTHERN
LAKES Radar
Ice Volcanoes
swaths of Titan’s
north pole reveal
lakes and seas (blue-
black). The heart-
shaped Ligeia Mare
is the second largest
sea on Titan and is
slightly larger than
Lake Superior.

NASA / JPL-CALTECH / ASI / USGS / UNIVERSITY OF ARIZONA

SIMULATED FLYOVER In a 3-D computer model of
Titan’s surface, created from Cassini data, scientists dis-
covered a 1-km-high peak and a 1.5-km-deep pit (shown)
in a region called Sotra Facula. Green marks possible vol-
canic areas, including potential flows that spread outward
from the pit. A blend of water, ammonia, and methane
erupting from the pit could explain the features, though
scientists still debate whether Titan has cryovolcanism.

Cologne, Germany), who uses detailed climate models to

study connections between Titan’s lakes and atmosphere.
These conditions would encourage methane to condense
NASA / JPL-CALTECH / USGS

and rain back out — primarily over and near the sea. Sur-
face darkening associated with cloud activity has indeed
appeared near Ontario Lacus, suggesting that rain wet the
ground shortly before the images were taken. Hayes thinks
these particular features are too far from Ontario Lacus for
the rain to have been generated by Tokano’s mechanism, but

PEELING THE PEACH Titan’s fuzzy orange glow is the only

thing visible in a natural-color composite (left), but the surface
appears in images taken in near-infrared light (middle) and in a
composite of visual and infrared wavelengths (right).

NASA / JPL / SPACE SCIENCE INSTITUTE (3)

30 March 2013 sky & telescope

NASA / JPL

RAIN-FED RIVERS Cassini’s radar revealed this canyon system on Titan in 2009. The channels flow from high plateaus to lowland areas, and their
many tributaries suggest that rainfall erodes the surface.

the process could still work elsewhere.

Answers could come in the near future. Brown and Backyard Titan Observer
his colleagues have used 3-D simulations to track Titan’s Amateur astronomers can help monitor Titan’s weather, too, says
weather cycle. They suggest that the methane accumu-
Ralph Lorenz. At the moment Titan appears fainter than magni-
lates in polar regions during summer, then somehow
travels — either on or below the surface — to lower tude 9, and although it’s above the horizon most of the night it’s
latitudes and evaporates. Their work not only predicts the only 0.8 arcsecond wide, making it a challenging target to resolve.
rare, intense rainstorms observed in low latitudes, but Short-exposure and video imaging can circumvent seeing problems,
also that clouds should form around the north pole in the especially if you stack images. Under good skies a skilled backyard
next two years, as that hemisphere transitions to sum- observer with a suitable telescope just might resolve Titan’s disk,
mer. With those clouds should come precipitation, raising
says Lorenz.
northern lake levels over the next 15 years. These changes
should be clearly observable by Cassini. Amateur observations could bridge the gap between Cassini and
Determining the final answer to how Titan’s weather whatever comes next. It looks increasingly like that gap will be large:
cycle works might have to wait for another surface no flagship-class mapping missions are on NASA’s budgetary hori-
mission. NASA didn’t select the proposed Titan Mare zon. In the meantime, a 20-centimeter telescope with a commercial
Explorer from its list of Discovery-class applicants, but
CCD can obtain useful spectra of seasonal changes in Titan’s haze.
European scientists are in the early stages of explor-
ing a similar project to sail a Titan sea. Called the Titan Several years ago Antonin Bouchez (Caltech), then a grad student
Lake In-situ Sampling Propelled Explorer (TALISE), the doing CCD photometry with a 35-cm telescope in Pasadena, suc-
mission would send a probe to float on Ligeia Mare, one cessfully plotted Titan’s light curve from night-to-night variations
of the moon’s largest seas. Perhaps that mission’s future as the moon rotated, although he wasn’t able to conclusively deter-
discoveries, paired with Cassini’s phenomenal work, will
mine that the transient bright spots he saw were clouds. Atmo-
help solve the case of Titan’s mysterious evaporation. ✦
spheric structure can also be measured during stellar occultations.
Donald F. Robertson is a freelance writer based in San Fran- You can find out more about observing Titan with amateur equip-
cisco. See www.donaldfrobertson.com for more of his work. ment on Lorenz’s website: www.lpl.arizona.edu/~rlorenz.

Sk yandTelescope.com March 2013 31

 Long-Distance Astronomy

Revitalize Your

Webinars can add variety and depth

to your club gatherings — without
breaking the budget.

32 March 2013 sky & telescope

Club Meetings
Tom Field
Want to watch someone run from a room Tacoma Astronomical Society invited Puckett to speak via
faster than an Olympic sprinter? Suggest the web. Without leaving his home in Georgia, Puckett
that he or she serve as the speaker coor- spoke to the groups about his supernova-search experi-
dinator for your club meetings. It’s a tough job and few ences, discussing the tools and skills needed for the job,
people want it. Whether you live in a big city or a rural as well as the challenges involved. Afterwards, club mem-
area, it can be an enormous challenge to arrange engag- bers posed questions to Tim in a two-way Q&A session.
ing talks month after month. Yet many clubs have man- “Many clubs, including ours, don’t have the budget to
aged to dramatically expand their pool of public speakers, fly speakers into town,” explained David Ingram, one of
even in the most remote locations. Rather than relying on the meeting’s organizers. “We had never hosted a webinar
local talent, these clubs invite lecturers to appear live over speaker and were a bit apprehensive, but it worked won-
the web from anywhere in the world. derfully. It was almost like Tim was in the room with us.”
Now, I know what you’re thinking. Web-based talks? “Our meeting attendees were really excited to have
Wouldn’t that be too impersonal? And wouldn’t the a chance to listen to such an important and well-known
quality of the presentation suffer? Years ago, watching a expert,” Ingram added. “In fact, we are so happy with
presentation over the web meant enduring grainy video
and poor voice quality. But, as I’ve learned from firsthand
experience, advancements in technology have vastly
improved the quality of remote presentations.
Without leaving my office, I’ve spoken for dozens of
clubs in locations all over the world, and I’ve received rave
reviews. Meeting attendees feel like I’m right there with
them because in addition to high-quality video, most soft-
ware now includes two-way audio, enhancing interaction
during Q&A sessions. I can even see the audience from
where I’m sitting in my office in Seattle.
ALL ILLUSTRATIONS ©BIGSTOCKPHOTOS.COM / JENNIFER MCCORMICK
More and more clubs have discovered that web-based
presentations (commonly called webinars) can re-energize
their club meetings by making available a larger com-
munity of fascinating speakers. Businesses regularly use
webinars for cross-country and even international meet-
ings; why shouldn’t amateur astronomers do the same?

WWW: World Wide Webinars

Last year, three clubs in the Seattle area wanted to hear
from renowned imager and supernova hunter Tim Puck-
ett. So the International Dark-Sky Association/Dark Skies
Northwest, the Seattle Astronomical Society, and the

Sk yandTelescope.com March 2013 33

 Long-Distance Astronomy

ings, and not just in the U.S. In the past year, I’ve talked
with clubs on four continents, including the imagers at
Norman Lockyer Observatory, U.K., the Scope-X confer-
ence in South Africa, and several clubs in Australia. Dis-
tance isn’t a factor, except when speaking from the U.S. to
a club Down Under — I needed several cups of coffee to
stay up long after midnight!

Making Webinars Work for Your Club

Webinar speakers can enrich club meetings, but before
hosting a webinar, make sure you have web access. Fortu-
nately, access speed from your club’s meeting site doesn’t
TOM FIELD

have to be blazingly fast — if you can conduct a video

chat from your meeting room, you probably have enough
NOT SO REMOTE Tom Field has used Cisco WebEx to talk bandwidth. In fact, since the live video window in a webi-
with clubs across four continents from the comfort of his nar is typically a small window on the screen, you need
Seattle office. The software shares his slides, shows his video even less bandwidth than a full-screen video call requires.
image, and allows him to highlight important features just as In most cases, the hosting club won’t need special
one would do with a laser pointer. He can even see and hear software. Speakers would host the show on their com-
the audience as he speaks.
puter, selecting from a wide range of webinar software
programs. One option is Skype, the video-chat software
the outcome that we’re planning to use the web to host a program. If speakers install Skype Premium, they can
variety of other remote speakers at other meetings in the share their PowerPoint slides, along with live video of
near future.” themselves. Personally, I prefer to use online programs
Puckett agreed — he felt that the presentation, his fi rst specifically designed for webinars, such as Cisco WebEx,
by webinar, had gone smoothly. “I’m actually surprised because the screen updates more quickly and the program
more clubs aren’t asking for these kinds of remote presen- offers more flexibility. Other webinar programs include
tations,” Puckett mused. “It’s a great way for them to add Citrix GoToMeeting, Adobe Connect, or TeamViewer. Most
variety to their meeting agendas. I think this is the wave of these programs run right over the web with no local
of the future.” software installation required. And you’ll find that some
Webinars have become more common at club meet- of them are free for noncommercial use.

34 March 2013 sky & telescope

 Of course, Murphy’s Law can strike even the best tech-
nology. So in advance of the meeting, I always send the
hosting club a backup copy of my PowerPoint file. If we
happen to run into a technical glitch, the club moderator
can step through the presentation on the club computer
while I narrate over a cell phone held up to a microphone
feeding their public-address system. I’ve never had to
resort to using this backup, but it’s a comfort to know that
we have a fail-safe way for me to address the meeting in
case of technological problems.

Putting it all together

Now that you know how to host lectures from anywhere Preparing for Your 45 Minutes of Fame
in the world, you have an enormous speaker pool to draw
from. To find speakers who would be willing to appear Have you given a talk to your local club that you think other
remotely, you might have to dig a bit. Use your creativity. clubs might enjoy? Giving a presentation via the web isn’t all
Since distance is no longer a limit, contact speakers you’ve that different from giving one in person. A few tips will help
seen at NEAF, the Winter Star Party, or other gatherings you make the transition.
and star parties. You could also contact authors of articles
you’ve read online or in S&T. You can even turn to online • Practice, practice, practice. Once you’ve selected the
forums — if you belong to one, you might notice some webinar software you’ll use, learn the basics of how to start a
participants stand out as being well informed. (Of course, meeting, share your slides, and transmit your video image via
not every expert will be a good speaker. You might want webcam. Then practice giving your presentation over the web
to ask for a 5-minute demonstration or references from to your spouse, your children, or your friends — anyone who
groups he or she might have spoken to in the past.) will listen.
One resource that can help you find speakers is the
free lecture referral service offered by the Astronomy • Prepare a demo. Clubs will want to know beforehand if
Outreach Network. Founded by Scott Roberts of Explore you’re a good speaker. When making contact with a club, offer
Scientific, this site has a Lecturers page that lists a variety to do a short demonstration talk for the decision-makers or pro-
of speakers (www.astronomyoutreach.net). Clubs looking vide a “demo reel” showing a short clip of your presentation.
for webinar speakers can contact any of the speakers on
the site directly and ask them about their availability. (By • Test it out. It’s always a good idea to conduct a test session
the way, if you’re a speaker, or would like to be, I encour- with the host well before the actual webinar. Make sure that the
age you to list yourself there.) meeting room has adequate bandwidth to support your presen-
Some lecturers speak for free; others might ask for an tation, and confirm that the host club’s computer can hook up
honorarium. One budget-friendly possibility is to team to the public-address system.
up with other clubs and, as a group, invite the leaders
in the field to give presentations. With modern webinar • Decide how to do Q&A. Although not absolutely necessary,
software, the clubs don’t even have to be in the same place it’s helpful if a microphone and webcam are built into the meet-
— audiences in different locations (and with different ing room’s computer so that you can see and hear the audi-
computers) can listen and interact with the same speaker. ence. But even if a club’s computer doesn’t have a microphone,
Over the next several years, I think we’ll continue to the host can conduct Q&A with a cell phone. I’ve done this on
see more and more clubs using the web to host remote several occasions with good results.
speakers at their meetings. Webinars open up a whole
new world of potential presenters for your club. They not • Make eye contact. Look directly into your webcam during
only make the meeting coordinator’s job easier, your club your presentation.
members will thank you for the added variety and rich-
ness of your meetings. ✦ • Keep your audience engaged. Most webinar programs
offer drawing capabilities, so you can circle, highlight, or draw
Tom Field of Field Tested Software is the developer of the arrows for your audience to see on the screen. Highlighting key
real-time spectroscopy program RSpec. He enjoys giving talks points focuses your audience’s attention in the same way as a
over the web and has spoken to dozens of astronomy clubs and laser pointer does.
science classrooms around the world. You can see a recorded
video demonstration of one of his webinars at www.rspecastro • Ask for feedback. The day after your talk, ask your contact
.com/outreach. at the club what you could improve in your next presentation.
 Backyard Astrophysics

My Hunt for
COSMIC JETS
A crucial phenomenon throughout the universe
is visible in amateur scopes, but just barely.
Dave Tosteson
Astrophysical jets are common in the cosmos, may be unable to assimilate
but not in amateurs’ observing logs. We read about them all the infalling material, due
in regard to the physics of black holes, the shaping of to magnetic and hydrody-
galaxies, and the birth of stars — but not as observing namic forces. These forces
projects to tackle outdoors in the dark. I decided to try shape the excess into bipolar
changing that. (oppositely paired) jets.
Many different things in astronomy produce narrow Such jets are usually
outflows that go streaming away, on scales differing in hidden by thick material sur-
size by tens of millions of times. Individual stars squirt rounding the growing system. A stripped-bare exception
jets during their formation. The cores of whole galaxies stands in view within the dim Rosette Nebula in Mono-
can emit giant streams at nearly the speed of light. ceros, now high in the evening sky. The Rosette’s central
Think of jets as a cosmic recycling mechanism. They region is shown on page 39, with the tiny jet arrowed.
arise when too much material falls toward a massive cen- This jet is part of Rosette HH1, a Herbig-Haro object.
tral body. Infalling matter usually forms an orbiting disk These form a class of odd little nebulae named for George
as it gets close, for the same reason water draining from a Herbig and Guillermo Haro, who studied them 80 years
bathtub forms a whirlpool: angular momentum must be ago. They proved to be jets from protostars, often with
conserved. If the disk becomes overloaded, its inner part bright blobs or shells where the jet impacts the surround-
ejects the excess away from its poles at high speed — by ing medium. They sometimes change in just a few years.
extreme heat, magnetic fields winding up tightly and Travis Rector, now at the University of Alaska in
bursting away, or both. The processes are complex, not Anchorage, studied Rosette HH1 in 2003 and noted that
always alike, and not completely understood. its inner jet was distinctly visible telescopically. At 14th
That such a useful and efficient process repeats all over magnitude, it can be seen in an 8- to 12-inch telescope
the cosmos isn’t surprising. But for a lot of observers, the under a dark sky. With my 15-inch reflector at home sev-
visibility of jets in amateur scopes may be. eral years ago, under a less-than-ideal sky, I found the jet
and its outer bow shock fairly easily.
Protostar: Rosette HH1 Rector says that Rosette HH1 is one of just a few cases
The jets from prenatal stars are among the smallest and where the protostar and its inner jet are directly visible.
least powerful, but for telescope users, they have the ad- This is because stellar winds from the brilliant young
vantage of being relatively nearby. stars nearby have cleared out the usual obscuring mate-
A gestating star is normally hidden in the cocoon of rial. Thus, an object normally seen only at infrared and
dust and gas feeding its formation. Deep within this radio wavelengths is visible by eye.
cocoon, the protostar is typically surrounded by a proto- A related type of object is the V-shaped Gyulbudag-
planetary disk. The central body accretes material via the hian’s Nebula in Cepheus, coming from the variable
disk until it becomes massive enough to ignite hydrogen protostar PV Cephei. The nebula is a small open mouth
fusion and officially turn into a star. But the central mass in the wall of a large dark cloud, spewing what the profes-

36 March 2013 sky & telescope

 NASA/CXC/CFA/R. KRAFT; NSF/VLA/UNIV. HERTFORDSHIRE/M. HARDCASTLE; ESO/WFI/M. REJKUBA
sional literature calls a “giant Herbig-Haro outflow.” The
outflow itself is not visible, but the nebula lining its inner
portion is. About 1′ in size, it’s a favorite of large-scope
observers because it changes shape on a timescale of
months. It was easy to see in my 25-inch f/5 reflector.
You need photos to locate correctly such an off-the-
beaten-track object as this. An essential resource for
really-deep-sky observers is the Digitized Sky Survey
(DSS), based on the Palomar Observatory Sky Surveys.
Enter your object or coordinates at stdatu.stsci.edu/
cgi-bin/dss_form, choose either .gif or .fits image format,
and you’re served a frame as large as 1° square centered
on your chosen point. Gyulbudaghian’s Nebula is at right
ascension 20h 45m 58s, declination +67° 58′ 30″ (2000.0).

Active galaxy: Centaurus A

The southern galaxy NGC 5128, also known as the radio
source Centaurus A, is the closest active galaxy to us at
Above: Big, bright NGC 5128, also named Centaurus A, emits a
12 million light-years. Its nucleus may be in the early
powerful pair of jets blazing in radio (purple above) and X-rays
stages of a reignition. Its jets, however, are known mostly (shown as blue-white, green, yellow, and orange). This compos-
from their spectacular radio and X-ray images. Using my ite image also includes a visible-light view. Below: In this deep
32-inch under the dark sky of the 2011 Texas Star Party, visible-light image, only a few thin outer traces of the northeast-
I saw the visible-light traces of the northeastward jet as a ward jet show at all. But the little arrowed streak can be detected
faint wisp several arcminutes long. What I saw correlates in very large amateur telescopes. You’ll also need a very dark sky,
well with the streak arrowed in the image below. high magnification, and this image to find the exact spot.

EUROPEAN SOUTHERN OBSERVATORY

 Backyard Astrophysics

Active galaxy: M87 in Virgo to 50 million kelvins as far as a half light-year from the
Active galactic nuclei arise around the supermassive black star. The disk and its jets precess like a top with a 164-day
holes at the centers of galaxies, especially if the galaxy’s period, drawing a corkscrew, as seen in the small radio
inner region has been stirred up by gravitational tides, as image at the bottom of the page.
seems to be the case in Centaurus A. That galaxy seems to About twice a year, this wobble allows us a glimpse
be a tumultuous merger in progress, nearly completed. at the spectrum of the primary star that feeds the col-
M87, an easy find in small scopes at 10th magnitude, lapsed object. It seems to be a white, type-A supergiant
is one of the brightest giant elliptical galaxies in the heart of 11 solar masses. The pair’s orbital period is 13.08 days,
of the Virgo Cluster, 55 million light-years away, and is which corresponds to most of the variability in visible
thought to be the most massive of them. It contains one light (about 0.6 magnitude). The accretion disk seems to
of the most massive black holes known (6 to 7 billion solar have an additional wobble with a 6-day period.
masses) and is shooting one of the most famous visible- SS 433 is relatively bright for something so exotic,
light jets at close to the speed of light. Recent studies with hovering around magnitude 14.0. Although I saw it easily
the Hubble Space Telescope have shown variability within with the 25-inch scope from my home, it appeared stellar
it, likely as a result of interaction with surrounding gas. and I noted no hint of its jet.
This jet too is visible in large amateur scopes. In my I have also tried to view another microquasar in
25-inch at the Texas Star Party, I could see M87’s jet at our galaxy: V1487 Aquilae, or GRS 1915+105, located 5°
661× during good seeing. It extended northwest from the farther north. This one emits even faster jets and 40
core by one-third of the galaxy’s visible diameter. times as much power. But it’s twice as distant and heavily
obscured in visible light. At magnitude 20-plus, even its
Microquasar: SS 433 central point was out of reach in my 32-inch.
Once a mystery, the variable star SS 433 in Aquila was
the first “microquasar” discovered. It’s a hot binary sys- Quasar: 3C 273
tem in which a primary star feeds so much gas toward a The brightest quasar in the sky (though not the near-
collapsed object — either a neutron star or a black hole est) is 3C 273 in Virgo. It varies between magnitude 12
— that the X-ray-hot disk around the tiny collapsed object and 13, and at a distance of 2.0 billion light-years, it’s the
emits jets at a quarter the speed of light. This is an exact most distant thing that’s reasonably easy to see in most
miniature version of what happens close to the super- backyard scopes. Quasars are active galactic nuclei so
massive black hole in a quasar or active galactic nucleus bright that they outshine their surrounding galaxies. The
— just millions of times smaller. famous jet of 3C 273 is tiny. I saw it in my 25-inch at the
SS 433, located 18,000 light-years away, shows many Texas Star Party as an 8″-long structure extending south-
fascinating features, including radio blobs being ejected west from the quasar, as in the image at lower right.
every few minutes. Turbulence within the jets heats them Quasars were much more plentiful in the universe’s

γ +10°

α Altair

β AQUILA

2 22
Star magnitudes

DIGITIZED SKY SURVEY / COLOR COMPOSITING BY S&T: SEAN WALKER

3
+5°
4 19
5
6 6755
7 h m δ h m
8 19 40 19 20

At 14th magnitude, the microquasar SS 433 in Aquila is a

unique pickup for your observing list. No sign of its relativistic
corkscrew radio jets were visible. On the chart above, the little
black box between 19 and 22 Aquilae shows the field of the
Digitized Sky Survey view at right, which is ½° wide. The radio
image of the jets (inset) is from the Very Large Array. Watch a
movie of radio blobs being expelled along the inner parts of the
precessing jets at www.nrao.edu/pr/2004/ss433.
NRAO

38 March 2013 sky & telescope

 12
Mon

Almost lost in the vast Rosette Nebula in Monoceros, the protostellar jet Rosette HH1 (arrowed)
can be spotted with medium-large amateur scopes. The protostar that’s squirting it may end up as
a red dwarf or brown dwarf. Outlined here is the Rosette’s central boxy asterism of 6th- to 8th-
magnitude stars, ¼° long, as well as the field of the inset blowup. North is up in all images.
NASA / ESA / WILLIAM KEEL (2)

youth, when they had more material to work with. The Gamma-Ray Bursts
comparative scarcity of nearby quasars such as 3C 273 The most violent jets in the universe, one of the most
suggests that while the proper black-hole equipment powerful events of any kind, are what we see as gamma-
remains in galaxies everywhere, the processes that feed ray bursts (GRBs). These jets are thought to arise in a
the holes have died way down. special kind of core-collapse supernova. Narrow beams
of matter moving at just a hair under the speed of light
Ex-quasar: IC 2497 & Hanny’s Voorwerp punch from the core right out of the star; colliding par-
A quasar that turned off very recently, astronomically ticles within the beams generate the gamma rays. We see
speaking, is thought to lie in IC 2497, a 15th-magnitude a gamma-ray burst when one of these beams happens to
galaxy about 650 million light-years away in Leo Minor. be aimed at Earth. Looking down the barrel of the beast,
This is the spiral galaxy next to the curious Hanny’s astronomers can decipher fantastic processes billions of
Voorwerp (“Hanny’s Object”), a tattered green nebular light-years away, across most of the visible universe.
glob that a Dutch schoolteacher found in 2007 on a Sloan Several amateurs, including my friend Tim Parson,
Digital Sky Survey image while volunteering in the Galaxy have visually observed GRB afterglows by subscribing to
Zoo project (S&T: November 2011, page 28). The object the AAVSO International High Energy Network (www.
defied inquiry — until astronomers figured that within IC aavso.org/aavso-international-high-energy-network), which
2497, a quasar that we now see as dormant was shining was set up to image such things rapidly. Some observers
brightly until no more than 200,000 years ago as viewed have seen the fading afterglows hours after the arrival of
from Earth. We still see the quasar’s light striking the the gamma rays. So far I’ve been shut out in my attempts
Voorwerp from the side, making it glow — a form of to join this exclusive club.
delayed “light echo.” The Voorwerp also appears to have But maybe that’s just bad luck. On March 19, 2008, a
been shaped and eroded by a particle jet from the qua- record-breaking GRB went off at redshift 0.937, a look-
sar. At the 2012 Texas Star Party, several people spied the back time of 7.5 billion years — more than halfway back
Voorwerp through a 36-inch scope. It lies 20″ south of the to the Big Bang. An automated sky survey caught it
galaxy, which is located at 9h 41m 04.8s, +34° 43′ 55″. peaking at an incredible visual magnitude 5.8 for several
seconds. Had someone been watching just the right spot
At a distance of 2.0 billion in Boötes, this would have been the most distant object
light-years, 3C 273 in ever seen with the naked eye — by a factor of 3,000 — and
Virgo is the farthest thing certainly the brightest astronomical jet ever seen! ✦
you can see with a 6-inch
telescope. A much larger Dave Tosteson, a family-practice physician in Chisago City,
NASA / JOHN BAHCALL

scope is needed to detect Minnesota, has used his giant scopes to see brown dwarfs,
its jet as a very thin streak gravitationally lensed arcs, globular clusters in the Virgo
running from 12″ to 20″ to Galaxy Cluster, high-redshift quasars, and galaxies in the
the quasar’s southwest. Hubble Deep Field.

Sk yandTelescope.com March 2013 39

 New Product Showcase

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40 March 2013 sky & telescope

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 OBSERVING
March 2013

In This Section

44 Sky at a Glance 54 Exploring the Solar System: A Lunar Curiosity

44 Northern Hemisphere Sky Chart 55 Lunar Phases and Librations
45 Binocular Highlight: Messier Marathon Season 56 Deep-Sky Wonders: Sailing South
46 Planetary Almanac 58 Web Links: This Week’s Sky at a Glance
47 Northern Hemisphere’s Sky:
Fantasian Skies Additional Observing Stories:
48 Sun, Moon & Planets: 36 My Hunt for Cosmic Jets
Giants in the Dark
60 Going Deep: Celestial Fireworks
50 Celestial Calendar
50 Comet PanSTARRS at Dusk
51 The Zodiacal Light The remarkable planetary nebula NGC 2818 is discussed
52 Action at Jupiter in the Deep-Sky Wonders column on page 58.
53 Lunar Occultations PHOTOGRAPH: NASA / ESA / HUBBLE
53 Phenomena of Jupiter’s Moons HERITAGE TEAM / STSCI / AURA

SkyandTelescope.com March 2013 43

 OBSERVING orth
Sky at a Glance Using the Map
Go out within an hour of a time
MARCH 2013 listed to the right. Turn the map
a

Feb. 27 EARLY EVENING: The zodiacal light is on excellent around so the yellow label for the
– Mar. 12 display from dark locations at mid-northern lati- direction you’re facing is at the `
tudes. Look west starting about 80 minutes after

17 h
bottom. That’s the horizon. Above H
sunset for a huge, tall, left-sloping pyramid of light it are the constellations in front of Fa R
E DR b
reaching up toward Jupiter; see page 51. you. The center of the map is c C AC
overhead. Ignore the parts
in U O
L

g
of the map above horizons E c
1–2 NIGHT TO DAWN: Saturn rises around 11 p.m. S

N
you’re not facing.

E
d
on the night of the 1st roughly 5° left or lower left
of the waning gibbous Moon. The pair remains EXACT FOR LATITUDE
40º NORTH.
close for the rest of the night.

7–10 DUSK: Comet PanSTARRS (C/2011 L4) should a

become visible through binoculars, and possibly to

`
MINOR

BO
`
Th
the unaided eye, somewhere in this time frame. n
uba URSA
Look very low in the west shortly after sunset; see

Ö
_

TE
page 50 for details.

a
S

c
10 DAYLIGHT-SAVING TIME STARTS at 2 a.m. for

& izar
most of the U.S. and Canada.

¡
M
Arct

Alc

Di ig
pp
or
M5
V
urus

B
M82

er
1

M R
M81

b
12–18 DUSK: Comet PanSTARRS is expected to be most

_
CAN
M3

A SA
U
prominent this week. It’s immediately left of a

JO
ATI

_
_
very thin crescent Moon on the 12th and well below

a
R
E

`
a more substantial crescent on the 13th.

S
CI
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o

BERENICES
17 EVENING AND NIGHT: Jupiter is spectacularly

s
close to the waxing crescent Moon amid Aldebaran,
14

X
h

COMA

f
the Hyades, and the Pleiades.
Facing East

i

+
`
20 SPRING BEGINS in the Northern Hemisphere at

MINOR a
¡

the equinox, 7:02 a.m. EDT. Zenith

LEO
VIRGO

_
28, 29 NIGHT: The Moon, just past full, rises upper right b
` c CA f

LE
of Saturn on the 28th and below Saturn on the 29th.
¡ N P
CE

O Regu

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e
R

c
a

kl
M4
4

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Planet Visibility SHOWN FOR LATITUDE 40° NORTH AT MID-MONTH

lus
b
a

_
◀ SUNSET MIDNIGHT SUNRISE ▶
`

Moon _
M6
Mercury Visible with binoculars in late March E March 23 ¡
7
Moon c `
Venus Hidden in the Sun's glow all month March 26 _
S
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X 0°
Mars Hidden in the Sun's glow all month T
A
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Jupiter SW NW S
_ Al
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M48
C

ph
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ard
Saturn E S SW
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H
O

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Moon Phases
R

D
R
V

A
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Last Qtr March 4 4:53 p.m. EST New March 11 3:51 p.m. EDT
S

First Qtr March 19 1:27 p.m. EDT Full March 27 5:27 a.m. EDT
S UN MON TUE WED THU FR I S AT
Fa

a
1 2
c

_
g PYXI
in

SE 11h S
Galaxy AN _
3 4 5 6 7 8 9 TL
Double star IA `
10 11 12 13 14 15 16 Variable star
Open cluster c
Diffuse nebula VEL
17 18 19 20 21 22 23 A
Globular cluster
24 25
24 26 27 28 29 30 Planetary nebula

31 31 Facing
 Facing Gary Seronik
20
When Binocular Highlight
Late Jan. Midnight
+60° Early Feb. 11 p.m. Messier Marathon Season
+ Late Feb. 10 p.m. Every spring, the Sun’s journey along the ecliptic
_

h
¡

23
c Early Mar. 9 p.m. returns it to a Messier-free zone near the border
S b W Late Mar. Dusk between Pisces and Aquarius. During that brief period,
EU N it’s possible to log all 109 objects in the Messier catalog
PH These are standard times.
in a single night. The key word here is possible —
C E g

in c
`
actually accomplishing that goal is difficult. Invariably,

Fa
2
M5 A marathoners fight to claim globular cluster M30 before
EI

A
P it sets during evening twilight, and to glimpse galaxy
IO

D
`

31
+80°
SS M74’s faint glow before it’s overwhelmed by predawn

E
M
CA

M
light. But for binocular observers, these are just two

O
a _
a

R
among many significant challenges.

D
Even without the pressures and fatigue that
_

N
A
b
Polaris
¡ accompany a marathon session, tracking down all the

`
Messiers in regular binoculars will test your abilities.
3
To have a fighting chance, use binos that magnify at
M3
ub er
le
Do lust

ES
least 10×, and are either image-stabilized or mounted in
+80°
LIS
a
C

A
ARD some fashion. Good, detailed charts are also a must —

SC
M
34

P
_

ELO the Pocket Sky Atlas is particularly well suited to the task.
`
LU
M
a

CAM

I
U

In my non-marathon, binocular Messier survey, I was

P
ol

NG
_

Alg

able to observe every object but one: galaxy M91. Try

ES

`
U

ARI _
IA

a
E

as I might, this 10.4-magnitude puff ball eluded me. And

`

TR
S

M91 is by no means the only tough target. As I noted in

R
ella

+60°
h
E

2 the October 2012 issue (page 68), the list of challenging

Cap
GA

P
¡

LY Messiers is long even under ideal conditions. Fortu-

RI

nately, M91 and the swarm of similar galaxies west of

s
_

Pleiade

I C
M d

on Facing West
c

Epsilon (ε) Virginis are well placed during marathon

U
`

Moch 16 P T
M3 38
A

r I season. If you’re able to make good headway here, your

a
6

M L
E C
tally at the end of the night will be pretty impressive.
er
e

Jupit
7
M3

This year’s prime marathon weekends begin on

`

stor March 9th and 16th. How many Messiers will you see?
Ca
j
S

For observers working under decent skies, it should be

k
es

_
RU

llux
5

Po I possible to log more than half the catalog, and perhaps

Hyad
M3

IN
aran

`
c

¡
_

M significantly more. The fun, though, is in the challenge

TAU

CETU

+ 2
dr
GE Moon19
r1
— the results are secondary. ✦
Aldeb

b
+20° March a x
h tri
lla R
Be O M85
j
AT
CANIS OR NGC _ N
a U
MIN 2244 us
e
IO E Q COMA BERENICES
e
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42 M100
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ER

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5

_
M91
M47 + M88
_
M46 Sirius
_
` M90
` M86 M84
M41
–20° S M89
U M87
P
M93 S LE
NI
b M58
M60
CA JOR
SW

¡ M A BA ε M59
M 5h
g

LU n
ci
d
CO _
Fa –1 VIRGO
/ `
0 Watch a SPECIAL VIDEO
–40° PUPPIS 1
2 To watch a video tutorial on how to use the big sky
3 Star map on the left, hosted by S&T senior editor Alan
8h MacRobert, visit SkyandTelescope.com/maptutorial.
4 magnitudes

g South Sk yandTelescope.com March 2013 45

OBSERVING
Planetary Almanac
Mercury Sun and Planets, March 2013
March Right Ascension Declination Elongation Magnitude Diameter Illumination Distance

Sun 1 22h 47.6m –7° 41′ — –26.8 32′ 17″ — 0.991

Mar 1 11 21 31
31 0h 37.7m +4° 04′ — –26.8 32′ 01″ — 0.999

Venus Mercury 1 23h 07.5m –1° 42′ 8° Ev +3.7 10.1″ 4% 0.663

11 22h 34.2m –6° 03′ 13° Mo +2.8 10.6″ 8% 0.632

21 22h 30.3m –8° 59′ 24° Mo +0.7 9.1″ 31% 0.735

16 31
1 31 22h 57.7m –8° 14′ 28° Mo +0.2 7.7″ 49% 0.877
Mars Venus 1 22h 23.5m –11° 29′ 7° Mo –3.9 9.8″ 99% 1.701

11 23h 10.5m –6° 52′ 5° Mo –3.9 9.7″ 100% 1.713

1 16 31
21 23h 56.4m –1° 56′ 2° Mo –3.9 9.7″ 100% 1.721
Jupiter
31 0h 41.9m +3° 06′ 1° Ev — 9.7″ 100% 1.724

Mars 1 23h 28.3m –4° 20′ 11° Ev +1.2 4.0″ 100% 2.352

16 0h 11.1m +0° 25′ 7° Ev +1.2 3.9″ 100% 2.380

31 0h 53.5m +5° 06′ 4° Ev +1.2 3.9″ 100% 2.406

Jupiter 1 4h 23.4m +21° 06′ 87° Ev –2.3 39.2″ 99% 5.034

31 4h 40.1m +21° 46′ 61° Ev –2.1 35.9″ 99% 5.498

16 Saturn 1 14h 38.5m –12° 46′ 119° Mo +0.4 17.9″ 100% 9.287

31 14h 33.9m –12° 18′ 150° Mo +0.3 18.6″ 100% 8.936

Saturn Uranus 16 0h 28.9m +2° 23′ 12° Ev +5.9 3.4″ 100% 21.024

Neptune 16 22h 22.5m –10° 48′ 22° Mo +8.0 2.2″ 100% 30.909

Pluto 16 18h 47.5m –19° 42′ 74° Mo +14.1 0.1″ 100% 32.659

16 The table above gives each object’s right ascension and declination (equinox 2000.0) at 0 h Universal Time on selected
dates, and its elongation from the Sun in the morning (Mo) or evening (Ev) sky. Next are the visual magnitude and
Uranus equatorial diameter. (Saturn’s ring extent is 2.27 times its equatorial diameter.) Last are the percentage of a planet’s disk
illuminated by the Sun and the distance from Earth in astronomical units. (Based on the mean Earth–Sun distance, 1 a.u. is
Neptune 149,597,871 kilometers, or 92,955,807 international miles.) For other dates, see SkyandTelescope.com/almanac.
Planet disks at left have south up, to match the view in many telescopes. Blue ticks indicate the pole currently tilted
Pluto 10"
toward Earth.

+40° 22h 20 h 18h 16h 14 h 12h 10 h 8h 6h 4h 2h 0h

Vega RIGHT ASCENSION
BOÖTES Castor
+30° CYGNUS +30°
Pollux GEMINI
Jupiter Pleiades ARIES
+20° HERCULES Arcturus LEO 16 +20°
PEGASUS
22 19
A QUILA Regulus
Uranus +10°
TIC
+10° CANCER
TA U R U S
LIP
OPHIUCHUS
Venus VIRGO
EC
Betelgeuse
Procyon
Mercury AQUARIUS ORION E Q U AT O R Mars
Saturn Mar 26-27
Neptune Rigel
–10° 8 LIBRA
–10°
DECLINATION

Spica Sirius
Pluto 5 31 H Y D R A E RIDA N US
–20° Mar 2 C O R V U S –20°
CAPRICORNUS CANIS
–30° Fomalhaut Antares MAJOR
–30°
SAGITTARIUS SCORPIUS
LOCAL TIME OF TRANSIT
–40° 10 am 8 am 6 am 4 am 2 am Midnight 10 pm 8 pm 6 pm 4 pm 2 pm –40°

The Sun and planets are positioned for mid-March; the colored arrows show the motion of each during the month. The Moon is plotted for evening dates in the Americas when it’s waxing (right side
illuminated) or full, and for morning dates when it’s waning (left side). “Local time of transit” tells when (in Local Mean Time) objects cross the meridian — that is, when they appear due south and
at their highest — at mid-month. Transits occur an hour later on the 1st, and an hour earlier at month’s end.

46 March 2013 sky & telescope

OBSERVING
Fred Schaaf has authored
Northern Hemisphere’s Sky 13 books on astronomy. Fred Schaaf

Fantasian Skies
Some star myths span entire sectors of the sky.

Raindrop fireflies sparkle on the shop blinds,

Echoes of summertime flicker in the street signs,
Terminal eyes at the edge of the night. . . .

Terminal eyes
Only the lonely Fantasian skies.
Terminal eyes
Calling you home from your restless disguise.
Al Stewart, Terminal Eyes

These next few months, I want to take us on an

unusual tour of spring’s evening skies. It will be orga-
nized around sky myths so big and potent that they link
together a number of constellations.
Unlike the Fantasian skies of Al Stewart’s 1973 song,
this particular kind of sky fantasy isn’t lonely. Indeed, it’s
so rich with names, images, and characters that it adds Taurus the Bull squares off against Orion in this mirror-reversed
a social dimension to the starry heavens — and helps us chart from Johannes Hevelius’s 1690 star atlas.
better remember and appreciate the locations of interest-
ing celestial sights. that the Orion Nebula is just below the Belt, the star clus-
The Orion myth-group. Although much of the great ter M41 just below Sirius, and M1, the Crab Nebula, very
Perseus myth-group of constellations has set by the time close to Zeta (ζ) Tauri, one of the horn-stars of Taurus.
of our all-sky map, the Orion myth-group is still well The Argo myth-group. Castor and Pollux, the Gemini
placed for observation. Twins, sailed on Jason’s great ship, the Argo. And in
One Greek myth about Orion describes his lascivious ancient times, the giant constellation Argo Navis lay far to
chase of the seven Pleiades sisters. The Pleiades used to the south of Gemini. In the 18th century Argo was divided
be considered a full-fledged constellation, but they’re now into three constellations: Puppis the Stern, Vela the Sails,
part of Taurus. and Carina the Keel. Unfortunately, Carina remains per-
Another ancient myth states that Scorpius killed manently below the horizon from latitude 40°° north.
Orion. But Orion is already setting by the time Scorpius East of Puppis and north of Vela is Pyxis the Box Com-
rises: that’s the whole point of this story. pass, another nautical constellation created when Argo
Fortunately, Orion the Hunter is so bright that was divided. Hercules was also an Argonaut for a while —
skywatchers have always connected it with neighboring but his constellation hasn’t risen yet at this hour.
constellations in simple situational dramas. So Canis There is one more constellation which belongs in the
Major and Minor, the Big and Little Dogs, which follow Argo myth-group, however. Low under Lepus and Canis
the Hunter west across the sky each night, must be that Major is Columba the Dove. This was the dove that the
hunter’s hounds. And the pattern of Taurus suggests a Argonauts released to test the Symplegades, rock cliffs
bull lowering its head to charge east — no doubt toward that would briefly pull apart and then smash together
Orion, who must face the onslaught. Finally, Lepus the again. The bird just barely got through, though losing
Hare is just south of Orion and west of Canis Major, so some tail feathers, so Jason judged the Argo could get
perhaps it’s the Big Dog’s quarry. through, too — and it did, losing just a bit of its stern.
The detailed geometry of the Orion myth-group seems What’s interesting for observers about the Argo myth-
almost too good to be true. Orion’s Belt points northwest group are its many bright stars and open clusters (see page
to Aldebaran and southeast to Sirius — and is equidistant 56). Argo sails on the Milky Way band, its stars almost
from both. For telescopic observers it’s also wonderful directly behind us on our journey around the galaxy. ✦

Sk yandTelescope.com March 2013 47

OBSERVING March’s Sun, Moon & Planets
OBSERVING
Sun, Moon & Planets

Giants in the Dark

Jupiter and Saturn take turns shining high on March nights.

Five of Earth’s seven fellow major bright for you to see its 1.2-magnitude EVENING AND NIGHT
planets are difficult or impossible to see in light without optical aid. Jupiter treks past Aldebaran and the Hyades
March. Three have conjunctions with the Mars moves even closer to the Sun as in March, appearing about 2/3 of the way up
Sun, and two more have conjunctions in the month progresses, so we won’t be able the sky at dusk on the 1st and still halfway
adjoining months: Neptune on February to see its phenomenally close conjunction up in the west at dusk on March 31st. The
21st and Mars on April 18th. Sadly, this with Uranus on March 22nd. According behemoth world dims from magnitude –2.3
means that when Mars and Uranus meet to master astronomical calculator Steve to –2.1 this month, and its apparent diam-
on March 22nd — the closest conjunction Albers, this is the tightest conjunction of eter diminishes from 39″ to 36″.
of two planets since 1942 — the event will two planets between 1942 and 2022. Mars Perhaps most fascinating, however, is
be unobservable. is closest to Uranus at 18:17 UT, when their the naked-eye or binocular view of Jupiter,
There is some good consolation for centers are just 39″ apart, and it passes due which is now picking up speed with direct
observers, however. Jupiter and Sat- north of Uranus 10 minutes later. (eastward) motion against the stars. Jupiter
urn, the two planets that remain visible This occurs during dusk in England, passes due north of light-orange Aldeba-
throughout March, are well placed for but the two planets are less than 5° above ran, remaining slightly more than 5° from
observation and appear unusually interest- the horizon at the moment of sunset. It’s this brighter (magnitude +0.8 or +0.9) of
ing right now. conceivable that Mars (magnitude 1.2, 3.9″ Taurus’s two eyes. Many people consider
In addition, a comet low in the dusk wide) will be detectable through a tele- 3.5-magnitude Epsilon (ε) Tauri, the north-
may grow sensationally bright. scope, but Uranus (magnitude 5.9 and 3.4″ western end of the Hyades V, to be Taurus’s
wide) seems out of the question. other eye. Jupiter passes just 2.1° from
DUSK Comet PanSTARRS (C/2011 L4) is the Epsilon on March 8th but ends the month
Mars may still be visible through binocu- real excitement this month. It may reach 4° from the star.
lars and telescopes a bare 3° or so above magnitude zero or brighter as it passes Aldebaran, Epsilon, and Jupiter form a
the western horizon a half hour after through perihelion within the orbit of Mer- straight line on March 1st and a nearly isos-
sunset on March 1st. The sky will be too cury on March 10th. See page 50 for details. celes right triangle on March 31st.

19
These scenes are
β Tauri
March 15 –18 March 22 – 25 always drawn for near
Around 9 pm Around 9 pm Moon the middle of North
Moon Mar 22 America (latitude
Mar 18 Sickle 40° north, longitude
of 90° west); European
LEO observers should
γ move each Moon
Moon Jupiter Moon
Mar 23 symbol a quarter of
Mar 17
the way toward the
Regulus
Aldebaran one for the previ-
Hyades Pleiades ous date. In the Far
East, move the Moon
Moon HYDRA
Moon halfway. The blue 10°
Mar 16 Mar 24 scale bar is about
Alphard the width of your fist
at arm’s length. For
clarity, the Moon is
Moon shown three times its
Mar 15 Moon
Mar 25 actual apparent size.
Looking West, halfway up Looking Southeast, high in the sky

48 March 2013 sky & telescope

Fred Schaaf welcomes your comments at fschaaf@aol.com. Fred Schaaf

O R B IT S O F THE P L ANE T S
The curved arrows show each planet’s move-
December
ment during March. The outer planets don’t solstice
change position enough in a month to notice at
this scale.
Earth
March Sun Mars
Mercury Sept.
equinox
Venus equinox
L AT E N I G H T
Saturn, in Libra, brightens marginally
June solstice
from magnitude +0.4 to +0.3 on its way
toward opposition in late April. Saturn
starts March rising around 10 or 11 p.m.
(depending on where you live in your time
Jupiter
zone) but ends the month rising less than
Uranus
an hour after twilight ends. It’s highest in Saturn
the south in the hours after midnight.
Neptune
Saturn is now retrograding (moving
westward against the stars) and enlarges
the gap between it and Alpha Librae from Pluto
4½°° to 5½° this month. The rings remain
magnificent, closing imperceptibly from a
19.2° tilt to an 18.8° tilt.

DAWN
Mercury goes through inferior conjunc- ers at mid-northern latitudes, likely visible tic makes a shallow angle with the dawn
tion with the Sun on March 4th and only through binoculars and telescopes. horizon at this time of year. So even by
emerges into dawn view late in the month. Although Mercury moves out to a greatest late in the month, Mercury appears very
But this is a poor apparition for skywatch- elongation of 28° on March 31st, the eclip- low in the east-southeast in bright dawn.
Venus reaches superior conjunction
with the Sun on March 28th at 17 h UT, so
March 27 – 29 γ Vir Jupiter March 29 –31 it’s not visible this month. Uranus arrives
Around 11 pm Around 9 pm at conjunction with the Sun only 8 hours
Aldebaran later. Neptune and Pluto are theoretically
observable in early dawn by the end of
Hyades March, but they’re both painfully low.
Moon Pleiades
Mar 27
MOON AND SUN
Spica
The Moon is waning gibbous when it rises
late in the evening on March 1st, upper
right of Saturn. It’s below Saturn by the
Moon following dawn. The waxing lunar crescent
Mar 28 is very close to Jupiter on the evening of
March 17th, between it and Aldebaran. The
second waning gibbous Moon of the month
Saturn
appears well upper right of Saturn on the
α Cet evening of March 28th, and well below
Moon Saturn the next evening.
Mar 29 The Sun reaches the March equinox
at 7:02 a.m. EDT on March 20th, crossing
the celestial equator to initiate spring in
Looking West the Northern Hemisphere and autumn in
Looking Southeast
the Southern Hemisphere. ✦

Sk yandTelescope.com March 2013 49

OBSERVING
Celestial Calendar

Comet PanSTARRS at Dusk

Awaited for nearly two years, will it be a spectacle or a speck?

If you don’t already have an observing pick up the comet first. After mid-March,
spot with a view very low to the west and skywatchers north of 40° N will be the ones

K. ROCHOWICZ / E. GUIDO / N. HOWES / G. SOSTERO

northwest, find one now — and plan to be seeing the comet higher than the charts
there after sunset each clear evening in indicate. See the caption for how to draw
early and mid-March. There will be Comet your own horizon line on the left chart.
PanSTARRS (C/2011 L4), likely to be the Through April and May the comet dims
best comet in several years for observ- as it climbs high into the north. Current
ers at mid-northern latitudes. It may or predictions put it at magnitude –0.2 on
may not be easy to see low in the twilight; March 10th, 1.3 on the 20th, 3.6 on April
bring binoculars. Its head could become 1st, 6.7 on May 1st, and 8.7 on June 1st. It
as bright as magnitude zero, but because passes within 5° of the north celestial pole
this is apparently a fresh comet making its The comet was still a 13th-magnitude bit of fluff on May 28th and remains in the far north-
in Hydra on September 10th, when a group of
first venture into the inner solar system, it ern sky through the first half of the sum-
astronomers in Italy imaged it remotely with a
could yet fade below expectations. mer, requiring larger and larger telescopes
2-meter telescope in Australia.
Comet PanSTARRS was still between as it departs back into the outer dark.
the orbits of Jupiter and Saturn, 7.9 a.u. though at a fairly distant 1.10 a.u. from us. On April 4th, PanSTARRS will pass 2°
from the Sun, when the PanSTARRS Mid-northern skywatchers can expect west of M31, the Great Andromeda Galaxy,
automated sky-survey project in Hawaii it to be at its best from about March 8–20, when they should be about equally bright.
discovered it at 19th magnitude almost especially March 12–17. On April 21st for North America, it goes
two years ago. It will reach perihelion, its The charts below are drawn for a almost across the big, dim galaxy IC 10,
closest point to the Sun, on March 10th skywatcher at our standard latitude of 40°° whose 11th-magnitude light is spread over
at a solar distance of 0.30 a.u., inside the north. Your difference from this latitude a region 0.1° wide in Cassiopeia. At that
orbit of Mercury. It’s likely to grow a large will matter in early March, and again from time the comet should be magnitude 6.
tail by that time. The comet is nearest to mid-March onward. Early in the month, For updates, keep an eye on skypub
Earth around the same date, on March 5th, southerners are best placed and are likely to .com/panstarrs.

20° Dusk, March 7– 20 Dusk, March 20 – May 31

30 minutes after sunset 50° 1 hour after sunset
Moon
March 13 May 31
40° 27
Polaris
23
19
30°
18 19 Mar 15
10° 15 16 17 20 11
13 14
7
12 20° May 3
11 Moon
29
10 March 12 25
Mar 20 24 28 Apr 1 5 21
9 10°
9 13 17
8
Mar 7 W NW N

260° 270° 280° 290° 300° 310° 320° 330° 340° 350° 0° 10°

Left: Look west a half hour after sunset; this chart shows the altitude and azimuth (compass direction) where PanSTARRS will be — if you’re at latitude
40° north. At other latitudes, draw a diff erent horizon on the diagram as follows. Find your latitude’s difference from 40° north. (For instance if you’re at
32° N, it’s 8°.) Using a protractor, draw a line through the horizon’s West point tilted by that much. Tilt the left side of your line down if you’re south of
40°, or up if you’re north of there. Right: As the comet fades, it moves higher in twilight or night. Ten degrees is about a fist-width at arm’s length.

50 March 2013 sky & telescope

 Bright Prospects! Alan MacRobert
–2 The predicted
0
brightness of
Comet PanSTARRS
The Zodiacal Light
2 as of December.
Magnitude

Perihelion
6

SEIICHI YOSHIDA /
AERITH.NET
10

12
December January February March April May June
2012 2013
κ Apr
26

Below and right: The dates along this 136

plot of the comet’s track are for 0h UT.
The tails point away from the Sun. 129
Apr
IC 10 22 β
2h ε 1h Apr 0h 23h ι 22h
vdB 1
30 C E P H E US
κ
225 A
Apr 26
+60° δ
γ 7790 M52
457 β ζ
Apr δ
η
22 ε
α Apr 7789
LACERTA
18
ζ
CASSIOPEIA β
RS

Apr α
+50° 14
anSTAR

185 147
φ
Apr
10 λ
Comet P

M31 Apr κ
6 ι ο
+40° ANDROMEDA
Path of

μ
Star magnitudes

Apr 2 2
β 3
4
π 5
6
Moonless February and March evenings are excellent times for spotting
Mar 29 the zodiacal light as twilight fades away. This is the season when the ecliptic
+30° δ
— the plane of the solar system — tilts highest with respect to the western
ε α β dusk horizon for skywatchers at mid-northern latitudes. The zodiacal light is
interplanetary dust, mostly from disintegrated short-period (Jupiter-family)
Mar 25 comets, that has gradually spiraled into the inner solar system. It’s lit up
by sunlight. Jim Saueressig II took this shot from Kansas on the evening of
η ζ
υ March 2, 2011. The zodiacal light runs from Jupiter low in Pisces up left of
Aries toward the Pleiades in Taurus.
+20°
Subtle as it may be, the zodiacal light is actually the brightest thing in the
Mar 21 PEGASUS
solar system after the Sun. It reflects more total sunlight than Venus or Ju-
PISCES α piter, as you would see if you could collect it all into one spot. The “zodiacal
γ light” around other stars could prove to be a serious obstacle to detecting
the light of any small planets that may be orbiting within it.

Sk yandTelescope.com March 2013 51

OBSERVING
Celestial Calendar
Jupiter’s Moons
Mar 1
Action at Jupiter
2 Earth is leaving Jupiter behind in 9:21, 19:17; 12, 5:12, 15:08; 13, 1:04, 11:00,
March as we speed along our faster orbit 20:55; 14, 6:51, 16:47; 15, 2:43, 12:38,
3 EAST WEST
around the Sun. Jupiter is still in fi ne 22:34; 16, 8:30, 18:26; 17, 4:22, 14:17;
4 view high in the south to southwest as 18, 0:13, 10:09, 20:05; 19, 6:00, 15:56;
twilight ends, but it shrinks from 43 arc- 20, 1:52, 11:48, 21:43; 21, 7:39, 17:35; 22,
5
seconds wide on February 1st to 39″ on 3:31, 13:27, 23:22; 23, 9:18, 19:14; 24,
6 Europa March 1st and 36″ on April 1st — quite a 5:10, 15:06; 25, 1:01, 10:57, 20:53; 26,
bit smaller than Jupiter’s 48″ around its 6:49, 16:45; 27, 2:40, 12:36, 22:32; 28,
7
December opposition. 8:28, 18:23.
8 Any decent telescope shows Jupiter’s March 1, 4:21, 14:17; 2, 0:13, 10:08,
four large Galilean moons. Binoculars 20:04; 3, 6:00, 15:56; 4, 1:52, 11:47,
9 Io usually reveal at least two or three. 21:43; 5, 7:39, 17:35; 6, 3:31, 13:26, 23:22;
10 Identify them with the diagram at left. 7, 9:18, 19:14; 8, 5:10, 15:05; 9, 1:01,
On the facing page are all of the moons’ 10:57, 20:53; 10, 6:49, 16:44; 11, 2:40,
11
many interactions with Jupiter’s disk and 12:36, 22:32; 12, 8:28, 18:24; 13, 4:19,
12 shadow in March. 14:15; 14, 0:11, 10:07, 20:03; 15, 5:58,
13
Jupiter’s Great Red Spot is becoming 15:54; 16, 1:50, 11:46, 21:42; 17, 7:38,
harder to identify as the planet shrinks. 17:33; 18, 3:29, 13:25, 23:21; 19, 9:17,
14 Following are the times, in Universal 19:13; 20, 5:08, 15:04; 21, 1:00, 10:56,
15
Time, when the Great Red Spot should 20:52; 22, 6:48, 16:43; 23, 2:39, 12:35,
cross Jupiter’s central meridian. The 22:31; 24, 8:27, 18:22; 25, 4:18, 14:14;
16 dates, also in UT, are in bold. The Red 26, 0:10, 10:06, 20:02; 27, 5:57, 15:53;
Ganymede Spot appears closer to the central merid- 28, 1:49, 11:45, 21:41; 29, 7:37, 17:33; 30,
17
ian than to the limb for 50 minutes 3:28, 13:24, 23:20; 31, 9:16, 19:12.
18 before and after these times: To obtain Eastern Standard Time
19 February 1, 1:07, 11:03, 20:59; 2, from UT, subtract 5 hours; for Eastern
6:54, 16:50; 3, 2:46, 12:42, 22:37; 4, Daylight Time (which begins March
20 8:33, 18:29; 5, 4:25, 14:20; 6, 0:16, 10:12, 10th), subtract 4. The times above
21 20:07; 7, 6:03, 15:59; 8, 1:55, 11:50, 21:46; assume that the spot is centered at about
9, 7:42, 17:38; 10, 3:34, 13:29, 23:25; 11, System II longitude 190°.
22

23
PERSEUS 29 Minima of Algol
24
18 Feb. UT Mar. UT
25 30
1 17:05 2 9:19
26 Callisto
38 4 13:54 5 6:08
27
7 10:44 8 2:58
Algol 21
28 10 7:33 10 23:47
29 13 4:23 13 20:36

30 16 1:12 16 17:26
34 18 22:01 19 14:15
31 TRIANGULUM
21 18:51 22 11:04
On February and March nights, Perseus declines in
the northwest. Estimate Algol’s brightness using the 24 15:40 25 7:54
The wavy lines represent Jupiter’s four big satellites. The central comparison stars above, labeled with their magnitudes
vertical band is Jupiter itself. Each gray or black horizontal band is (decimal points omitted). At right are Algol’s predicted 27 12:29 28 4:43
one day, from 0h (upper edge of band) to 24h UT (GMT). UT dates mid-eclipse times, when it will be magnitude 3.4 instead
of its usual 2.1. 31 1:32
are at left. Slide a paper’s edge down to your date and time, and
read across to see the satellites’ positions east or west of Jupiter.

52 March 2013 sky & telescope

Our new Jupiter app shows the Galilean moons and the Great Red Spot at any time. Go to the iTunes store and search for JupiterMoons.

Lunar Phenomena of Jupiter’s Moons, March 2013

Occultations Mar. 1 8:35
9:54
I.Tr.I
I.Sh.I
Mar. 9 1:31
3:50
III.Tr.I
III.Tr.E
10:46
10:47
II.Tr.E
III.Sh.I
15:51
17:11
II.Sh.E
III.Sh.E
10:46 I.Tr.E 5:40 II.Tr.I 10:50 II.Sh.I Mar. 24 8:57 I.Tr.I
12:05 I.Sh.E 6:47 III.Sh.I 13:09 III.Sh.E 10:10 I.Sh.I
21:26 III.Tr.I 7:47 I.Oc.D 13:12 I.Ec.R 11:08 I.Tr.E
23:44 III.Tr.E 8:06 II.Tr.E 13:15 II.Sh.E 12:21 I.Sh.E
Mar. 2 2:46 III.Sh.I 8:14 II.Sh.I Mar. 17 6:58 I.Tr.I Mar. 25 5:36 II.Oc.D
3:03 II.Tr.I 9:07 III.Sh.E 8:14 I.Sh.I 6:12 I.Oc.D
5:06 III.Sh.E 10:39 II.Sh.E 9:10 I.Tr.E 8:06 II.Oc.R
5:28 II.Tr.E 11:16 I.Ec.R 10:25 I.Sh.E 8:06 II.Ec.D
5:39 II.Sh.I Mar. 10 5:01 I.Tr.I Mar. 18 2:51 II.Oc.D 9:36 I.Ec.R
5:51 I.Oc.D 6:18 I.Sh.I 4:14 I.Oc.D 10:35 II.Ec.R
8:04 II.Sh.E 7:12 I.Tr.E 5:21 II.Oc.R Mar. 26 3:27 I.Tr.I
9:21 I.Ec.R 8:29 I.Sh.E 5:27 II.Ec.D 4:39 I.Sh.I
Mar. 3 3:04 I.Tr.I Mar. 11 0:08 II.Oc.D 7:40 I.Ec.R 5:38 I.Tr.E
4:22 I.Sh.I 2:16 I.Oc.D 7:56 II.Ec.R 6:50 I.Sh.E
5:15 I.Tr.E 2:38 II.Oc.R Mar. 19 1:28 I.Tr.I 23:46 III.Oc.D
6:33 I.Sh.E 2:49 II.Ec.D 2:43 I.Sh.I Mar. 27 0:21 II.Tr.I
21:27 II.Oc.D 5:17 II.Ec.R 3:39 I.Tr.E 0:41 I.Oc.D
23:56 II.Oc.R 5:45 I.Ec.R 4:54 I.Sh.E 2:12 III.Oc.R
The waxing crescent Moon occulted 3rd-
Mar. 4 0:10 II.Ec.D 23:30 I.Tr.I 19:33 III.Oc.D 2:43 II.Sh.I
magnitude Zeta Tauri as seen from Nor-
0:20 I.Oc.D Mar. 12 0:47 I.Sh.I 21:40 II.Tr.I 2:48 II.Tr.E
mandy, France, on April 25, 2012. Mohamed
2:38 II.Ec.R 1:41 I.Tr.E 21:57 III.Oc.R 4:04 I.Ec.R
Laaifat shot this series over the course of 3:50 I.Ec.R 22:43 I.Oc.D
2:58 I.Sh.E 4:39 III.Ec.D
about 50 minutes through a Meade 70-mm 21:33 I.Tr.I 15:23 III.Oc.D Mar. 20 0:06 II.Tr.E 5:09 II.Sh.E
f/5 ETX refractor. 22:51 I.Sh.I 17:46 III.Oc.R 0:07 II.Sh.I 7:05 III.Ec.R
23:44 I.Tr.E 19:00 II.Tr.I 0:38 III.Ec.D 21:56 I.Tr.I
Here are two nice lunar occultations for Mar. 5 1:03 I.Sh.E 20:37 III.Ec.D 2:09 I.Ec.R 23:08 I.Sh.I
your March celestial calendar: 11:16 III.Oc.D 20:46 I.Oc.D 2:33 II.Sh.E Mar. 28 0:08 I.Tr.E
• On the evening of March 19th, the dark 13:37 III.Oc.R 21:26 II.Tr.E 3:03 III.Ec.R 1:19 I.Sh.E

limb of the first-quarter Moon will black out 16:21 II.Tr.I 21:32 II.Sh.I 19:58 I.Tr.I 18:58 II.Oc.D
16:36 III.Ec.D 23:01 III.Ec.R 21:12 I.Sh.I 19:11 I.Oc.D
the 5.2-magnitude star 71 Orionis for tele-
18:47 II.Tr.E 23:57 II.Sh.E 22:09 I.Tr.E 22:33 I.Ec.R
scope users across most of North America 18:49 I.Oc.D 23:23 I.Sh.E
Mar. 13 0:14 I.Ec.R 23:54 II.Ec.R
except the Southwest and West. Some 18:56 II.Sh.I 17:59 I.Tr.I Mar. 21 16:13 II.Oc.D Mar. 29 16:26 I.Tr.I
times: from central Massachusetts, 11:02 18:59 III.Ec.R 19:16 I.Sh.I 17:12 I.Oc.D 17:37 I.Sh.I
p.m. EDT; Miami, 11:47 p.m. EDT; Chicago, 21:21 II.Sh.E 20:10 I.Tr.E 18:43 II.Oc.R 18:38 I.Tr.E
9:49 p.m. CDT; Denver, 8:33 p.m. MDT. 22:19 I.Ec.R 21:27 I.Sh.E 18:46 II.Ec.D 19:48 I.Sh.E

• On the morning of March 31st, observ- Mar. 6 16:02 I.Tr.I Mar. 14 13:29 II.Oc.D 20:38 I.Ec.R Mar. 30 13:40 I.Oc.D
17:20 I.Sh.I 15:15 I.Oc.D 21:15 II.Ec.R 13:43 II.Tr.I
ers south of a line from central Florida
18:13 I.Tr.E 15:59 II.Oc.R Mar. 22 14:27 I.Tr.I 14:05 III.Tr.I
through Oregon can watch the double 19:31 I.Sh.E 15:41 I.Sh.I
16:07 II.Ec.D 16:01 II.Sh.I
star Beta Scorpii, magnitudes 2.6 and 4.8, Mar. 7 10:47 II.Oc.D 18:36 II.Ec.R 16:39 I.Tr.E 16:09 II.Tr.E
emerge from behind the dark limb of the 13:16 II.Oc.R 18:43 I.Ec.R 17:52 I.Sh.E 16:29 III.Tr.E
waning gibbous Moon. Some times for the 13:18 I.Oc.D Mar. 15 12:29 I.Tr.I Mar. 23 9:50 III.Tr.I 17:02 I.Ec.R
bright component: Miami, 4:45 a.m. EDT; 13:29 II.Ec.D 13:45 I.Sh.I 11:00 II.Tr.I 18:27 II.Sh.E

Austin, 3:13 a.m. CDT; Los Angeles, 12:57 15:57 II.Ec.R 14:40 I.Tr.E 11:42 I.Oc.D 18:48 III.Sh.I
16:48 I.Ec.R 15:56 I.Sh.E 12:13 III.Tr.E 21:13 III.Sh.E
a.m. PDT. The faint component reappears
Mar. 8 10:31 I.Tr.I Mar. 16 5:39 III.Tr.I 13:25 II.Sh.I Mar. 31 10:56 I.Tr.I
up to a minute or two earlier. 11:49 I.Sh.I 13:27 II.Tr.E
8:00 III.Tr.E 12:06 I.Sh.I
For maps and timetables of these and 12:42 I.Tr.E 8:20 II.Tr.I 14:48 III.Sh.I 13:08 I.Tr.E
other occultations, see lunar-occultations 14:01 I.Sh.E 9:44 I.Oc.D 15:07 I.Ec.R 14:17 I.Sh.E
.com/iota/bstar/bstar.htm.
Gone are the days when backyard occul- Every day, interesting events happen between Jupiter’s satellites and the planet’s disk or shadow. The first columns give the date and
tation timers did cutting-edge work map- mid-time of the event, in Universal Time (which is 5 hours ahead of Eastern Standard Time; 4 hours ahead of Eastern Daylight Time).
Next is the satellite involved: I for Io, II Europa, III Ganymede, or IV Callisto. Next is the type of event: Oc for an occultation of the satel-
ping elevations along the Moon’s limb;
lite behind Jupiter’s limb, Ec for an eclipse by Jupiter’s shadow, Tr for a transit across the planet’s face, or Sh for the satellite casting its
lunar orbiters do it much better. But occul- own shadow onto Jupiter. An occultation or eclipse begins when the satellite disappears (D) and ends when it reappears (R). A transit or
tations are still fun to watch. ✦ shadow passage begins at ingress (I) and ends at egress (E). Each event is gradual, taking up to several minutes. Courtesy IMCCE.

Sk yandTelescope.com March 2013 53

 OBSERVING
Exploring the Solar System

A Lunar Curiosity
The author serendipitously rediscovers Larrieu’s Dam.

On the sultry evening of June 26, 2001, I trained an effect of atmospheric turbulence on a bright linear feature
8-inch reflector on the 6-day-old Moon. The seeing was against a black background could differ so dramatically
quite steady, with slow, low-amplitude turbulence that from its effect on the extended objects in the field and the
permitted sharp views at 240× ×. The morning Sun illu- detached sunlit peaks just beyond the terminator.
minated the face of the spectacular mountains of Rupes Confronted by one of the most striking illusions I’ve
Altai, a 480-kilometer (300-mile) curved segment of the witnessed in more than four decades of lunar observing,
rim of the giant Nectaris impact basin, which can tower I dashed inside and grabbed my copy of Antonín Rükl’s
to heights of 1 km above the surrounding terrain. Atlas of the Moon. After comparing Chart 57 to the view in
My eye was soon drawn to a brilliant hairline of light the eyepiece, it soon became apparent that the exceedingly
cutting across the receding shadows that filled several narrow thread of light was the unusually straight north-
depressions in the lunar foothills. Straight as an arrow western rim of the D-shaped crater Polybius K catching
and aligned roughly perpendicular to the Altai Scarp, this the first rays of the morning Sun. The lower slopes were
delicate feature appeared to slowly undulate as if it were still immersed in the deep shadows cast by the crater’s
tethered at one end and immersed in a gently flowing cur- eastern wall and the ridges to the north.
rent of water. Its “motion” called to mind a worm wrig- This memorable observation languished in my note-
gling at the end of a fish hook. All of the other features in book until 2008, when I stumbled across an article by
the field of view appeared essentially stationary, although Nigel Longshaw in the Journal of the British Astronomical
intermittently and subtly blurred. I marveled at how the Association recounting several independent rediscover-

Larrieu’s Dam

Larrieu’s Dam is a striking hairline of light that appears just

to the west of the Rupes Altai six days after new Moon.
Y. GORYACHKO / M. ABGARIAN / K. MOROZOV

54 March 2013 sky & telescope

 Contributing editor Thomas Dobbins observes the Moon and other denizens
of the solar system from his home in Fort Myers, Florida. Thomas Dobbins

ies of this obscure feature. Longshaw characterized it as

a prime example of those “minor lunar features seldom
described in the mainstream literature, yet which often
present an intriguing image in the eyepiece when cap-
tured under favorable illumination.”
First reported in 1955 by the French observer A. C. Lar-
rieu, who described it as “very thin and rectilinear” and
resembling a “bridge or hydraulic barrier,” the feature

Y. GORYACHKO / M. ABGARIAN / K. MOROZOV

was soon christened “Larrieu’s Dam” by the noted British Polybius K
historian of astronomy Richard Baum. Others have com-
pared its appearance to a brightly lit roadway stretching
across a reservoir fi lled with inky black water.
Located at lunar coordinates 25°S 25°E, Larrieu’s Dam
is visible under sunrise conditions on a waxing Moon
over colongitudes 343° to 355° (1.6 to 0.5 days before
First Quarter). Under ideal lighting it spans a length of
about 14 kilometers but subtends less than ¼ arcsecond As the Sun sets over the region, Polybius K is lost among the host of other small,
nondescript craters that dot the foothills of the Altai Scarp.
in width. It’s exceedingly narrow at its eastern extremity,
where the sunlit rim is only about 200 meters wide. Aper-
tures of 6-inches or more may reveal gentle swellings that Under sunset lighting at colongitudes 140° to 153°° (4
seem to correspond to slightly elevated segments. to 5 days after full Moon), the dramatic “thread of light”
Despite its modest dimensions, Larrieu’s Dam is easily appearance is absent, but a set of linear spurs running
discernible with a 60-millimeter refractor at a magnifica- down the crater’s outer wall are revealed. According to
tion of only 75× or so. Visual acuity is much better for lin- Longshaw, they resemble the buttresses of a dam.
ear objects than for point sources like double stars. As the Larrieu’s Dam is a mere curiosity, a trick of light and
British author J. B. Sidgwick explained in his classic Ama- shadow. Yet I am compelled to wonder why such a cap-
teur Astronomer’s Handbook: “A linear object may stimulate tivating phenomenon that is repeated once every month
a sufficient number of cones to produce sight even though and persists for more than a day went unheralded for so
its width is 20 or 30 times less than the threshold diameter many years. How many comparable spectacles still lie in
of a spot.” store for lunar observers? ✦

The Moon • March 2013

Mar. 1
Phases Distances
27
LAST QUARTER Perigee March 5, 23h UT
March 4, 21:53 UT 229,881 miles diam. 32′ 18″
NEW MOON Apogee March 19, 3h UT
March 11, 19:51 UT
251,196 miles diam. 29′ 33″
FIRST QUARTER
March 19, 17:27 UT Perigee March 31, 4h UT
228,357 miles diam. 32′ 31″
FULL MOON
March 27, 9:27 UT
Librations
For key dates, yellow dots Ulugh Beigh (crater) March 1
14 indicate which part of the Casatus (crater) March 5
S&T: DENNIS DI CICCO

Moon’s limb is tipped the

most toward Earth by libration Humboldt (crater) March 14
under favorable illumination. Galvani (crater) March 27
5

Sk yandTelescope.com March 2013 55

OBSERVING
Deep-Sky Wonders

Sailing South
Puppis and Pyxis host some amazing clusters and nebulae.

Last month we navigated the northern reaches of Pup- make a 4½′ zigzag with the amplitude of the zigs decreas-
pis, part of the mythical ship Argo crewed by Jason and ing from northeast to southwest. Another 20 stars, mostly
the Argonauts on their heroic quest for the Golden Fleece. fainter and to the northeast, expand the cluster to 8′.
We’ll now set a course for southern Puppis and then Virginia amateur Mike Klosterman brought up the
swiftly sail into eastern Pyxis. Representing a magnetic unusual star pattern in NGC 2567 at Florida’s Winter Star
compass, Pyxis may seem a fitting addition to Argo, but Party a few years ago. We decided that it looks like ~1 in
the device was unknown to the ancient Greeks. The com- both the inverted view of his reflector and the mirror-
pass was added to the sky centuries later by the French reversed view of my refractor. Since some folks use the
astronomer and mathematician Nicolas Louis de Lacaille, symbol ~ to signify “approximately,” we dubbed this
who also divided Argo into three smaller constellations. group the Approximately One Cluster.
The northernmost deep-sky wonder on our tour is the The barred spiral galaxy UGCA 137 lies 8′ south of the
open cluster NGC 2571. In 14×70 binoculars it appears as yellow-orange star near NGC 2571. Although the galaxy’s
a nebulous patch sporting two stars in its center. My 105- magnitude is 12.4, its surface brightness is very low.
mm refractor at 87× shows about 25 stars of 9th magni- Despite this impediment, Finnish amateur Jaakko Sal-
tude and fainter, most forming an 8′ × 6′ M with rounded oranta drew an impressive sketch of UGCA 137 (shown at
peaks that point southwest. The cluster is quite irregular, lower left) as seen through his 120-mm refractor at 360×.
and it’s guarded by a 6th-magnitude, yellow-orange star The points at each end of the bar are superposed 14th-
20′ southwest. magnitude stars. Saloranta was observing at high altitude
Additional stars visible in my 10-inch reflector at 68× in Spain’s Canary Islands.
lengthen NGC 2571 to 13′, elongated southeast-northwest, NGC 2571, NGC 2567, and UGCA 137 give us a feel for
and some faint stars to the south plump its breadth to the depth of the sky with their distances of roughly 4,400,
about 8′. With the wide-angle eyepiece used for this obser- 5,500, and 60 million light-years, respectively.
vation, NGC 2567 occupies the southern part of the field Now we’ll drop several degrees southward to NGC
when NGC 2571 is consigned to the north. Most of its stars 2546. Through 15×45 binoculars this open cluster is a
large, ragtag group of many faint stars at the south-south-
western border of a big region of showy bright stars. My
Right: Finnish stargazer 10-inch reflector at 68× reveals 75 stars ranging widely in
Jaakko Saloranta sketched brightness and loosely strewn across 40′ of sky. A denser
UGCA 137 as seen through patch of stars decorates the cluster’s northwestern edge,
his 120-mm refractor at 360× and a 6th-magnitude star pins its south-southeastern rim.
from the island of La Palma Although the rest of the deep-sky wonders in our tour
at latitude 29° north. have about the same declination as NGC 2546, I’ve never
logged them from my upstate New York home. These
UGCA 137 observations were all made at Florida’s Winter Star Party,
where southern objects crest 18°° higher in the sky.
The same splashy collection of stars that hugs NGC
2546 also wears the compact emission nebula NGC 2579
on its eastern side. Through my 105-mm refractor at 153×,
Left: German stargazer it’s a little oval glow with a bright star embedded. The
NGC 2579 Uwe Glahn also traveled to nebula stands out much better when I use an O III filter.
La Palma, where he viewed NGC 2579 is quite obvious in my 10-inch scope at 118×.
and sketched these nebulae The bright star is nestled in the west-northwestern part
through his 20-inch Dobso-
ESO 370-9 (see the sketch at left), and a faint star is ensconced in the
nian telescope at 321×.
nebula’s brighter east-southeastern section. The faint star
shows up much better at 308×, and the nebula is more

56 March 2013 sky & telescope

Sue French welcomes your comments at scfrench@nycap.rr.com. Sue French

prominent with a narrowband nebula fi lter.

Some images of NGC 2579 show that both stars have
close companions. The bright star is actually a foreground
object, while the three faint ones are the hot blue stars of
spectral type O that are the sources of the ionizing radia-
tion that makes the nebula glow.
The 13½-magnitude, type-O star 1.2′ southwest of
NGC 2579 rests at the heart of the small emission nebula
ESO 370-9 and is responsible for its ionization. I didn’t
see this nebula with my 10-inch scope, but it has been
spotted in 14.5-inch and larger scopes. Can you spot it?
NGC 2579 and ESO 370-9 have been confused with
nearby objects and mistaken for reflection nebulae and
planetary nebulae. Their natures and identities were
unsnarled in a 2007 paper by Marcus Copetti and col-
leagues. The authors place these nebulae 25,000 light-
years away in the outer reaches of the galactic disk and
suggest that they may be physically related.
The stunning cluster couple NGC 2451 and NGC
2477 lies 4.6° west of NGC 2579 and 3.3° west-northwest
of Zeta (ζ) Puppis. The duo seems like an exaggerated
version of another striking Puppis pair, M47 and M46.
NGC 2451 is even looser and flashier than M47, while NGC
2477 looks finer grained and more compact than M46.
In my 105-mm refractor with a wide-angle eyepiece
giving a magnification of 17×, NGC 2451 and 2477 share S&T contributing editor Alan Dyer’s photograph of the rich star cluster NGC 2477
the field of view with plenty of room to spare. NGC 2451 is (left) and splashy 2451 (right) shows that the entire region is pervaded with faint
a large, sprawling, coarse group centered on a fiery orange nebulosity. The bright star near NGC 2451’s center is sometimes called c Puppis.

ρ h3945
2482 M93
2
2784 Tr 7 2362 ο2
Star magnitudes

3 2566 ξ
4 η ο τ 2354
κ –25°
5
θ 2559
2467
δ
6
7 δ γ 2527 2483
8 2571 Ru 44
ζ 3 σ
λ 2533 2489 ε
2627 η
PYXIS UGCA 137
ε 2567
2439 Cr 132 –30°
Cr 140
Ru 55
α w
CANIS MAJOR
IC 2469
2663
β PUPPIS
2579
q –35°
2818 h4063 2298
ε 2451 Cr 135
2546
k
VELA 2477 d π
l
ζ
9h 30m 9h 00m 8h 30m 7h 30m 7h 00m

Sk yandTelescope.com March 2013 57

OBSERVING
Deep-Sky Wonders

ember, the cluster’s brightest star. Another orange star

adorns the northeastern side of the cluster, and a yellow
one gilds the eastern edge. I count 40 mixed bright and
faint stars in 47′. NGC 2477 offers a lovely contrast to its
companion, displaying a beautiful, 23′ mound of minute
diamond chips growing more concentrated toward the
center and too densely packed to tally.
At 28× the clusters still inhabit a single field of view.
The arrangement of NGC 2451’s stars gives the delight-
ful impression of a multi-armed spiral galaxy. NGC 2477
yields up many more individuals, and a raggedy chain of
slightly brighter stars springs from its northeast quadrant.
NGC 2451 consists of two separate clusters along the
same line of sight, one at 600 light-years and the other at
1,000 light-years. As you’d expect from the faintness of
its stars, NGC 2477 is considerably more distant at 4,000
light-years.
Now we take our dogleg tack into eastern Pyxis to end
our voyage with NGC 2818, a remarkable pairing of an
open cluster and planetary nebula. James Dunlop discov- Daniel Verschatse captured NGC 2818, an unusual superposition
ered them on May 28, 1826, with the 9-inch reflector at his of a planetary nebula and open cluster, from Antilhue Observatory
home in Parramatta, New South Wales. Dunlop describes near his home in Santiago, Chile.

his find as: “A pretty large faint nebula of a round figure,

Clusters and Nebulae in Puppis and Pyxis 6′ or 8′ diameter; the nebulosity is faintly diff used to a
Object Type Mag(v) Size/Sep RA Dec. considerable extent. There is a small nebula in the north
preceding side, which is probably a condensation of the
NGC 2571 Open cluster 7.0 13′ 8h 19.0m –29° 45′
faint diff used nebulous matter; the large nebula is resolv-
NGC 2567 Open cluster 7.4 10′ 8h 18.5m –30° 39′ able into stars with nebula remaining.”
UGCA 137 Barred spiral galaxy 12.4 3.2′ × 2.3′ 8h 17.7m –30° 08′ Through my 130-mm refractor at 23×, the open cluster
is a rich gathering of extremely faint stars about 7′ across
NGC 2546 Open cluster 6.3 40′ 8h 12.4m –37° 37′ with an 11th-magnitude star at its northern edge. The
NGC 2579 Emission nebula 7.5 1.6′ × 1.5′ 8h 20.9m –36° 13′ stars are widely spread at 102×, and I count about 35
in the group. The planetary is a wonderful addition to
ESO 370-9 Emission nebula 13.0 1.1′ × 0.8′ 8h 20.9m –36° 14′
the cluster, sitting west of center. It’s large, quite oval
NGC 2451 Open cluster 2.8 50′ 7h 45.4m –37° 57′ east-west, and fainter at the tips. A brighter bar runs
NGC 2477 Open cluster 5.8 27′ 7h 52.2m –38° 32′
north-south across the nebula’s center. With the help of
a narrowband fi lter, the bar looks pinched in at its waist,
NGC 2818 Open cluster 8.2 9′ 9h 16.2m –36° 37′ but the filter wipes out most of the cluster’s stars.
NGC 2818 Planetary nebula 11.6 93″ × 55″ 9h 16.0m –36° 38′ Although NGC 2818’s cluster and planetary nebula
coincide on the dome of the sky, they’re generally thought
Angular sizes and separations are from recent catalogs. Visually, an object’s size is often smaller than to be unrelated. Their radial velocities (motion along our
the cataloged value and varies according to the aperture and magnification of the viewing instrument.
Right ascension and declination are for equinox 2000.0.
line of sight) are considerably different, so they are not
moving together through space. ✦

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Weekly TV Program skyweek.com week. Our free SkyWeek app for Apple and
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Books and Back Issues shopatsky.com star charts customized for your location.
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Steve Gottlieb
Going Deep

Celestial Fireworks
Three extraordinary galaxies congregate in and near Camelopardalis.

What’s the brightest northern galaxy not ing numerous sites of intense star formation. NGC 2403
included in the Messier catalog? You might be surprised resides at a distance of roughly 10 million light-years and
to hear that distinction belongs to 8.4-magnitude NGC is an outlying member of the M81 group — a collection of
2403, a prominent spiral that would be better known if it more than 30 galaxies neighboring our Local Group.
wasn’t isolated within the dimly lit outlines of the sprawl- NGC 2403 can be swept up in 50-mm binoculars as a
ing constellation Camelopardalis. hazy glow, and the galaxy is an impressive sight in 6- to
In terms of structure and size, NGC 2403 is a virtual 10-inch scopes. In good conditions, a 12-inch or larger
twin to M33. Both are late Hubble-type Scd spirals with scope will resolve a number of the brighter emission
small central bulges and chaotic spiral arms contain- regions that stud the spiral arms.
In my 18-inch Dobsonian the galaxy spreads out 12′
12h 10h 8h +70° × 5′ and broadly brightens to a 1.5′ core with a 12.5-mag-
Star magnitudes

2 nitude star pinned to its south side. With careful study,

3 CAMELOPARDALIS
DRACO 43 two fairly wide spiral arms emerge near the northwest
4 κ 2366 42 and southeast side of the central region and curl counter-
5
Holmberg II clockwise nearly 180°. The more prominent arm on the
6 λ M82 2403 northern side is separated from the core by a slightly
M81 π1 darker gap. Several stars are superposed in the halo,
+60°
URSA MAJOR π2 including two 10th-magnitude luminaries on the south-
δ α ο west and southeast sides.
The distribution of NGC 2403’s H II regions — pink
γ patches of hydrogen ionized by the ultraviolet radiation of
β υ LYNX
hot, massive O- and B-class stars — has been well studied
M97 M108 by professional astronomers. A 1965 catalog by French
00 8 30 8 00 7 30 7 0 astronomers Philippe Véron and Alain Sauvayre includes
8h 30m 8h 00m 7h 30m 52 H II regions (referred to here as VS 1 through VS 52),
4 and a comprehensive 1983 survey by Paul Hodge and
Star magnitudes

5 Holmberg II Robert Kennicutt netted more than 600 H II regions pep-

6 +70° pering the spiral arms. For the best view of these glowing
7 knots, head to dark skies, push the magnification up to
8 2366 250× to 350×,×, and use the labeled image on the facing
9
page to pick them off individually.
NGC 2404, located 1.7′ east-northeast of the galaxy’s
+68° center in the northern spiral arm, is the easiest H II
URSA MAJOR target. At 323× NGC 2404 appears fairly bright, 15″ across,
and irregularly round. This immense cloud of ionized
hydrogen is comparable in size to NGC 604 in M33 and
the Tarantula Nebula in the Large Magellanic Cloud, the
+66°
two largest stellar nurseries in our Local Group.
π1 2403 VS 3 is a fuzzy 12″ knot on the northwest side of the
halo, 3.4′ from the center. It forms a straight line with two
π2 14th-magnitude stars to its northeast. A bit tougher are
CAMELOPARDALIS VS 24 and VS 38, a pair of barely nonstellar 14th-magni-
tude knots at the north edge of the core. If you’ve made it

60 March 2013 sky & telescope

 VS 38 VS 24
VS 3
NGC 2404

SUBARU TELESCOPE / NATIONAL ASTRONOMICAL OBSERVATORY OF JAPAN

VS 52

5′
NGC 2403

HSK 45

Supergiant NGC 2363

HII Region

STEPHEN LESHIN
BERNHARD HUBL

5′ 5′
Holmberg II NGC 2366

this far, see if you can identify VS 52, a very dim glow at At first glance NGC 2366 appears as a low-surface-
the eastern tip of the spiral arm containing NGC 2404. brightness glow stretching 3.5′ × 1.0′ south-southwest
NGC 2403 has two unusual neighbors — the Mag- to north-northeast. But at the south end of the galaxy is
ellanic-type dwarf irregular galaxies Holmberg II (6.4°° an extraordinary 12th-magnitude starburst region that’s
to the northeast) and NGC 2366 (3.7° north). Swedish twice as luminous as the Tarantula Nebula. At 323× this
astronomer Erik Holmberg discovered Holmberg II high-surface-brightness knot appeared irregular in shape,
(also cataloged as UGC 4305) in 1950 during a survey of 15″ to 20″ in size, and occasionally resolved into two or
galaxies in the M81 Group. I can detect it easily at 175× in three components. Try using a narrowband filter — I
my 18-inch as a fairly faint, low-surface-brightness patch, found it increased the contrast of the knot and extin-
roughly 5′ × 3.5′ across. An 11th-magnitude star is near guished the glow of the galaxy.
the north edge and a trio of 12th- and 13th-magnitude Many sources misidentify this giant H II complex as
stars is superposed just east of center. NGC 2363. But NGC 2363 properly refers to a detached
Halton Arp, in his Atlas of Peculiar Galaxies, placed star cloud or independent satellite galaxy just west of the
Holmberg II (Arp 268) in the category of “Galaxies with south end of NGC 2366. I’d be interested in hearing if
irregular clumps” due to its numerous bubbles of glowing you’re successful in detecting this phantom glow. ✦
gas. My 18-inch only hints at these regions, but using Jimi
Lowrey’s 48-inch behemoth Dob in West Texas, I saw sev- Contributing editor Steve Gottlieb has observed almost all the
eral H II splotches in the central region, including a fairly NGC objects and many of the IC objects. Do a web search for
bright 15″ knot with the designation HSK 45. “Gottlieb NGC” to find his observing notes.

Sk yandTelescope.com March 2013 61

 S & T Test Report Dennis di Cicco

Celestron’s SkyProdigy 6
Could this telescope set a new standard for a beginner’s ideal instrument?

Celestron SkyProdigy 6
U.S. price: $999
Available from Celestron dealers worldwide.
www.celestron.com; 310-328-9560

Maybe it was the piercingly cold nights.

Or perhaps it was Orion marching out of the
eastern sky leading the seasonal parade of winter
constellations. But for whatever the reason, while
testing Celestron’s new SkyProdigy 6 telescope late
last fall, I kept envisioning the gift-giving holidays
ahead. I imagined budding amateur astronomers
unwrapping new telescopes on Christmas morning
in scenes that have played out with uncanny simi-
larity since the dawn of mass-marketed telescopes.
I knew the excitement these new telescope own-
ers would carry with them as they headed outside

Celestron’s SkyProdigy telescope line is the company’s

first to feature 100% automatic alignment, making its
computerized object-finding virtually foolproof for people
with limited knowledge of the night sky.
ALL PHOTOS BY THE AUTHOR
62 March 2013 sky & telescope
 WHAT WE LIKE:
on the first clear night to explore the Moon and perhaps Virtually foolproof auto- celestial viewing.
a bright planet or two. But I also knew the struggles matic alignment and Go Thickening haze almost
To pointing
and frustrations that would befall many of them as they scuttled my first night with
started looking for star clusters, nebulae, and galaxies. Intuitive hand control the SkyProdigy 6. The stars
That last vision, however, was one of Christmas past, Excellent 6-inch telescope of Cassiopeia were barely
because the coming holidays were sure to have many visible in the northwest as
WHAT WE DON’T LIKE:
newly minted observers receiving Celestron SkyProdigy I carried the scope to the
telescopes. For them, hunting celestial targets would be 6-inch telescope is near back deck of my suburban-
the upper limit for the
different. Dramatically different. mount and tripod
Boston home. The scope
There are five telescopes in the SkyProdigy line: is remarkably easy to set
70- and 102-mm achromatic refractors ($499 and $699, up, and the fully illustrated
respectively), a 90-mm Maksutov-Cassegrain ($599), a 130- quick-start guide walks you through all the steps, includ-
mm Newtonian reflector ($699), and the 6-inch Schmidt- ing ones that are blatantly obvious. It took me longer to
Cassegrain I tested. The telescopes are standard, time- unpack the box that the telescope was shipped in than
tested Celestron fare. It is the SkyProdigy alt-azimuth it did to assemble the various components into a work-
mount that makes them noteworthy. In addition to Go To ing telescope. Furthermore, the whole setup, including
pointing, the mount is Celestron’s first-ever with a self- the battery pack with eight D cells, weighs less than 23
aligning feature. Turn it on, and a built-in digital camera pounds (10 kg), so you can easily assembly everything
automatically finds stars to initialize the Go To point- inside and carry it outdoors in one trip.
ing and tracking. Once that’s done, you just press a few When I flipped the power switch on, I expected the
buttons to select things you want to see from the scope’s hand control to ask me to enter the date, time, and my
internal 4,000-object database (which includes planets, location — information typically required by Go To
stars, and deep-sky objects), and the scope points to them. scopes such as the SkyProdigy that aren’t equipped with
Yesterday’s science fiction has become today’s reality. a GPS receiver. But it didn’t. Instead, the scrolling display
When computerized Go To pointing was introduced said to just press the Align button. Doing so launched an
on modestly priced telescopes in the 1990s, it was widely automated sequence of events that Celestron calls its Star-
touted that it would revolutionize observing for beginners. Sense Technology. The internal camera (which is a fi xed
Many pundits felt that Go To technology would banish the part of the mount and not the telescope) snaps a picture,
difficulty of finding deep-sky objects for people unfamil- identifies stars, and determines where the telescope is
iar with star charts and the complexities of the moving pointed. It does this for three widely spaced locations on
celestial sphere. For some it did, but for too many others the sky, after which the scope is ready to use. The process
the technology failed. The problem usually came down to
the observer being unable to identify the stars needed to
initialize the Go To system.
The digital camera in Celestron’s SkyProdigy does the
star identification automatically. It’s not the first telescope
with that ability. Meade’s 6- and 8-inch LS (for Light-
Switch) scopes, reviewed in our December 2010 issue,
page 54, also have a built-in camera for star identification.
But with a starting price of $1,399, the LS series is a bit
steep for a typical beginner’s budget. Celestron’s starting
price of $499 is much closer to the amount many fi rst-
time telescope buyers are willing to spend.

First Night
We borrowed the 6-inch SkyProdigy from Celestron
for this review, since its weight would place the most
demands on the mount. If it worked, then the smaller
SkyProdigy scopes should perform equally well. Likewise,
the 6-inch scope’s low-power eyepiece has a 0.8°° field of Celestron’s StarSense Technology uses a
view — the smallest of any scope in the SkyProdigy line, digital camera (inside the small, red tube)
putting the most demands on the accuracy of the mount’s to identify stars and automatically initial-
ize the Go To pointing. Telescopes attach
Go To pointing. It’s also the most expensive scope in the
to the SkyProdigy mount with a standard
SkyProdigy line, but that extra cost gets you a scope with
Vixen-style dovetail.
enough “serious” aperture to give many observers years of

Sk yandTelescope.com March 2013 63

 S&T Test Report

took barely more than 2 minutes. A few button pushes let me select Jupi- indistinguishable from magic.” It’s not an
To a novice, this may all seem relatively ter from the database and send the scope exaggeration to say that SkyProdigy’s out-
simple, but it’s not. Furthermore, my sky slewing across the sky toward the giant of-the-box debut seemed a bit like magic.
conditions that evening were terrible. Had planet. When it stopped moving, Jupiter In the final minutes before the sky
the StarSense camera really found enough was at the edge of the eyepiece field. Not completely closed in, I did a quick calibra-
stars for the internal pattern-matching perfect pointing, but close enough to be tion that I had earlier read about in the
algorithms to figure out where the scope successful. Next, I sent the scope to the scope’s manual. I returned to Capella
was pointed? And wait a minute, I never bright star Capella in Auriga. It too ended and, using the direction keys on the hand
entered the date, time, or my location. I up at the edge of the field. What about control, centered the star in the scope’s
know it’s possible to gather the necessary Auriga’s well-known star clusters M36, eyepiece. I then selected the calibrate
information from a set of star-field images M37, and M38? Bing, bing, bing, the scope routine from the hand control’s Utilities
— interplanetary spacecraft have similar found all three, even though the haze was menu. The process took only a minute,
abilities as a backup in case their primary making it increasingly difficult for me and I did it by following the instructions
navigation systems hiccup. But had this to see them in the eyepiece. The whole displayed on the hand control. The calibra-
relatively inexpensive telescope just done experience reminded me of the comment tion teaches the StarSense system where
it in 2 minutes under my crummy sky by the late science-fiction author and the center of the telescope’s field is, and it
conditions? It didn’t seem possible, but I visionary Arthur C. Clarke, who noted that improves the alignment and Go To perfor-
was about to find out. “any sufficiently advanced technology is mance when you next use the scope.

A Few Details
The SkyProdigy 6 worked equally well on
subsequent nights. StarSense Technology
never failed to achieve automatic align-
ment when the sky became dark enough
for the camera to find stars, which usually
occurred between 45 minutes and an
hour after sunset. The main requirement
for a good automatic alignment is for the
telescope to have a reasonably clear sweep
of about half the sky in a clockwise direc-
tion from where it is initially pointed (the
initial position can be in any direction).
This was the case from my back deck, but
barely so, since the house blocked about
half of the sky. In locations where there
are lots of trees or buildings, you can do a
StarSense alignment by manually point-
ing the telescope at three unobstructed
parts of the sky. The quality of this align-
ment (and subsequence Go To pointing)
may be reduced if the sky locations are not
well separated.
The StarSense camera doesn’t work in
daylight, but you can still align the mount
for Go To pointing and tracking. This
requires using the Sun (after acknowledg-
ing appropriate warnings displayed on the
hand control), Moon, or any planet as a
single alignment point. (You can also use
Left: Simple features such as a bubble level, hand-control bracket, and accessory tray make the Sky-
this alignment method in twilight when
Prodigy a pleasure to use. The mount attaches to the tripod with a single, captive hand-knob and a
conical fitting — it’s extremely easy to assemble, even in the dark. Upper right: The optional SkyQ
it’s too bright for the camera to find stars.)
Link WiFi module ($99) lets you control the scope with Celestron’s SkyQ app for Apple’s iPhone, But the procedure requires you to enter
iPad, and iPod Touch. It works very well, but requires a manual alignment rather than one using your geographic location (and it’s a good
the automatic StarSense procedure. Bottom right: Large, illuminated buttons make the SkyProdigy idea to confirm that the scope’s internal
hand control easy to operate in the dark even while wearing heavy winter gloves. clock, which was set when the telescope

64 March 2013 sky & telescope

Although this is an extreme example from the
author’s early nights of testing (the protective
paper hadn’t yet been removed from the candy-
apple red tube), most observers will want an
aftermarket dew cap or dew heater if they have
the SkyProdigy Schmidt-Cassegrain or Maksu-
tov telescopes. Despite the obviously bad condi-
tions, the StarSense camera never fogged up.

was manufactured, has the correct time).

The LCD on SkyProdigy’s hand control
displays scrolling-text instructions for Top: The StarSense Technology works under a wide variety of less-than-favorable sky conditions,
operating the scope. Cold weather makes including moonlight and urban light pollution. This view shows what the author was up against on his
the LCD sluggish, rendering this text first night with the SkyProdigy (described in the accompanying text). Above: The SkyProdigy 6 comes
illegible, but it’s only a problem if you with a star diagonal and 25- and 9-mm eyepieces that yield magnifications of 60× and 167×, respec-
haven’t yet learned the scope’s basic func- tively. The red-dot finder is useful for manually aiming the scope at celestial targets that you don’t
tions or don’t have the printed manual know by name, after which you can identify them with a single button press on the hand control.
at hand. Some of the scope’s lesser-used
features, such as the calibration process The Optics 5 seconds to settle out. That’s relatively
mentioned above, display instructions that Because Celestron optics are already long, but the numbers alone don’t tell the
you have to manually scroll with buttons highly regarded, most of my testing was entire story. Given the scope’s excellent
on the hand control. As such, they were focused on the SkyProdigy mount. Nev- optical quality, coupled with its easy set up
readable even on the coldest nights — a ertheless, the 6-inch Schmidt-Cassegrain and foolproof Go To pointing, the overall
nice feature. easily lived up to the company’s reputa- observing experience was superb. The
The scope’s illustrated manual is well tion. My views of the Moon, Jupiter, and SkyProdigy is the most straightforward
done, with clear and concise information. Saturn were first rate. And although I do Go To telescope I have ever used.
But there are a few goofs that might trip up much of my own deep-sky observing with It’s unlikely that a group of telescope
a beginner. For example, I found several larger apertures, the 6-inch can show a lot, experts could ever agree on what consti-
names in the manual that didn’t match especially when it comes to the brighter tutes a “perfect” beginner’s telescope, but
what was printed or displayed on the hand- objects that most beginning observers I think that many would feel as I do — the
control. Likewise, some of the scrolling text turn to first. SkyProdigy is getting pretty close. ✦
on the hand control refers to the “Option” The telescope is, however, close to the
button, but you’ll need the manual to weight limit that the mount can ade- Although he knows it’s a lot, senior editor
learn that this button is the one with the quately handle. Vibrations that jiggled the Dennis di Cicco doubts that he can recall
Celestron logo at lower left on the keypad. view as I turned the focus knob took about every Go To telescope he’s used.

Sk yandTelescope.com March 2013 65

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 Gary Seronik
Telescope Workshop

My Outback Travelscope
Built to take flight, this 8-inch Dob makes the grade
with today’s baggage regulations.

In this magazine’s December 2001 issue I solar eclipse and some dark-sky observing in the Outback,
described my airline-portable 8-inch Dobsonian. That I decided it was time to rebuild my travelscope for safe
scope was a big hit with readers, and I’ve logged a lot of transport in my checked luggage.
miles with it over the years. But if you fly regularly these To achieve this goal, I needed to make two major
days, I don’t need to tell you how precious overhead stor- changes. First, the new scope had to be compact enough
age space has become. I began to fear that someday my to fit inside my suitcase with enough extra space for a few
scope would be “gate checked” and end up being tossed inches of protective padding. Second, it needed to go on a
into the luggage hold with all the other checked bags, diet. The original scope weighed 25 pounds (11 kg). When
where it might not fare very well. Thus, when my plans packed into my 10-pound suitcase, I had only 15 pounds
were laid for travel to Australia for last November’s total of the airline’s 50-pound weight budget remaining for
my eyepieces, cameras, clothes, and everything else that
travels in my checked bag.
I started planning my Outback travelscope with the
premise that the lightest and most compact design would
likely require the greatest amount of field assembly. But
I was fine with that. When I fly for stargazing events, I
usually spend a few days at my destination, so setup and
teardown isn’t a nightly ritual. I also decided to use the
8-inch, f/4.2 primary mirror, as well as the secondary
mirror and holder, from my original travelscope. I would
build everything else from scratch with an eye towards
trimming as much weight as possible without sacrificing
stability or rigidity.
A conventional Newtonian’s tube mainly serves to
hold the optical elements and focuser in their correct
positions. The key to making a minimalist Dob is to find
other ways to accomplish this task. In the case of my new
travelscope, the “tube assembly” consists of a secondary
cage and the cell for the primary mirror joined by a pair
of aluminum struts. Arriving at the design required a lot
of rough sketches, weighing components, and a generous
helping of trial and error.
I used ½-inch plywood for the main parts and ¾-inch
for the side-bearing rings. I worked with a jigsaw to cut
out as much excess wood as possible from the rocker-
box panels, leaving the remaining wood in the form of
triangular elements, which offered maximum rigidity. At
the travelscope’s front end I saved weight by reducing the
GEORGE BRANDIE

The author with his travelscope ready for a night of south- original scope’s secondary cage to a single plywood ring
ern-sky observing in the Australian Outback, near Uluru. with a plate that accommodates the focuser, and a pair
of mounting blocks that act as supports for the curved-

Sk yandTelescope.com March 2013 67

 Telescope Workshop

GARY SERONIK (3)

Far left: Weighing only 15 pounds
(7 kg), the travelscope functions
like a regular Dobsonian. The
side bearings are attached with
hand knobs that thread into holes
tapped in the aluminum struts.

Above: The rocker-box panels are

seen prior to assembly. The large
cutouts reduced the weight of the
mount by nearly half.

Left: A view of the travelscope’s

optical tube during test assembly.
This step is crucial for determining
the scope’s balance point so that
the side bearings can be correctly
positioned, which in turn sets the
minimum height of the rocker box.

vane secondary holder. At the back end I dispensed with to a stable support is to ensure that the scope’s weight is
a traditional Dobsonian’s mirror box and simply attached transferred directly to the tripod legs. Although the tripod
the aluminum struts directly to the rear disk of the is additional weight, it’s an item I always take with me for
double-plate mirror cell. The front ring, rear mirror-cell photography.
plate, and side bearings share the same 11-inch outside One aspect of this travelscope that isn’t apparent
diameter, so I saved construction time by using just one in pictures of it fully assembled is that the individual
setting on my router’s circle-cutting jig. Likewise, the parts are made to fit together inside the rocker box, for
secondary ring and side bearings also share the same safe transport. With the exception of the ground board,
8¾-inch inside diameter. everything is secured by a pair of bolts that pass through
To complete the tube assembly, I dispensed with holes in all the parts and the bottom of the rocker box.
the original scope’s four, ½-inch aluminum poles and Once I tighten down a pair of wing nuts, the individual
replaced them with a pair of 29¼-inch-long, 1-inch- components are locked down and ready to be packed into
square aluminum tubes. Since fewer struts meant less my suitcase.
mounting hardware, the weight savings were multiplied. So how did my new travelscope perform on its maiden
I glued sockets (consisting of ¼-20 T-nuts mounted in voyage? Beautifully. The new design trimmed 10 pounds
wooden cubes) into the ends of the square tubes. As off the original, resulting in a lightweight, 15-pound pack-
such, the front ring and rear mirror cell can be attached age. The scope made it to Australia (and back) unharmed
to the struts with socket-head cap screws. This two-strut in a checked suitcase, and it took me only 10 minutes to
arrangement turned out to be more rigid than my previ- assemble the scope in my hotel room. Best of all, I had an
ous four-pole configuration. 8-inch scope in the Outback to explore the wonders of the
I made two versions of the scope’s ground board. The far-southern skies from a dark location. All it took was an
first is a tabletop design that is simply a round disk of ply- hour of blissfully scanning the Large Magellanic Cloud
wood with three Teflon pads on its top side and three feet for me to be convinced the effort was worthwhile. ✦
underneath. The second is a more elaborate assembly that
attaches to my Bogen camera tripod. This ground board is Contributing editor Gary Seronik combines travel and star-
similar to the one described in the December 2007 issue gazing whenever possible. More information on his travel-
as part of my Easy-Go-Round binocular mount. The key scope is available at www.garyseronik.com.

68 March 2013 sky & telescope

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 Aurora Photography

70 March 2013 sky & telescope

Northern
Exposure Follow these simple suggestions to
take stunning aurora photographs.

Babak A. Tafreshi Neither of these events guarantees beautiful auroras,

but either can increase the possibility of one.
It’s March 5, 2012. I’m sitting at Auroras can last anywhere from a few minutes
my computer and checking the to several hours. For a successful imaging session,
website spaceweather.com for you should plan to run your camera throughout the
the latest news on solar activity. entire night.
A giant sunspot has appeared on Most auroras appear a pale green color that is
the solar limb, roaring with potential X-class flares easy to see because our eyes are most sensitive to
and gas eruptions that could shower Earth’s magne- the green region of the spectrum. Purple, blue, and
tosphere with streams of solar-wind particles. This yellow are sometimes visible during strong activity,
activity might cause spectacular auroral displays dur- and deep red auroras will appear in the most intense
ing the next two weeks. It’s time to pack! storms. Even a faint aurora that appears colorless
Viewing a strong auroral display is the experience visually might be dramatically colorful in your
of a lifetime. The magical lights shimmer and dance photographs. An aurora’s color comes from photons
in colorful rays, forming ever-changing shapes in the emitted by oxygen and nitrogen atoms and molecules
sky. If you’re anxious to see a majestic display, March in our atmosphere after they’re excited by solar wind
is a great time of year. Plus, the current solar cycle is particles spiraling along Earth’s magnetic field.
expected to peak in 2013, promising numerous flare
events and major auroras. Gearing Up
Individual auroras are unpredictable. Some are the Capturing stunning aurora pictures, like all types of
result of coronal mass ejections (CMEs) that launched photography today, has been revolutionized by digital
off the Sun days earlier, while others are produced SLR cameras. Even with a modest point-and-shoot
by high-speed solar wind particles shooting toward digital camera, auroras are easy and fun to photograph
Earth from coronal holes (see the cover story of last with the proper settings. If you’re planning a trip to
month’s issue for an in-depth discussion of auroras). shoot auroras, here’s a list of things to take along.
First, bring two cameras. One camera can be a
Capturing the aurora borealis is fun and easy, but unless backup to your primary camera, or you can use it to
you live near the Arctic Circle, you’ll need to travel to catch capture additional stills of alternate parts of the sky
a bright display. Contributing photographer Babak Tafreshi while your main camera is snapping frames for a
captured this display of the northern lights from northern time-lapse video. Also, because your target is a large
Sweden. All images are courtesy of the author. swath of the aurora and not faint nebulosity, many

Sk yandTelescope.com March 2013 71

 Aurora Photography

of the new budget multi-megapixel cameras with small

pixels will work well for photographing bright auroras.
However, small pixels often saturate point sources such
as stars, and they have lower dynamic range at high
ISOs (1600 or greater). Although not essential, full-frame
DSLRs with large pixels generally provide better color
performance overall in aurora photography, though rapid
developments in sensor technology are beginning to
counter this oft-stated rule of thumb.
If your main camera is a DSLR, then a high-quality,
wide-angle lens with a fast focal ratio will produce your
best images. Bargain lenses from third-party manufactur-
ers tend to produce distorted star images and flaring near
the edge of the frame, seriously degrading the overall
quality of your photos. Also, avoid wide-range zoom
lenses such as 18-to-200-mm and 24-to-105-mm. Zoom
lenses are often much slower photographically than
fi xed-focal-length lenses. A wide-angle f/2 lens will record
much fainter auroras in shorter exposures than an f/3.5
zoom. Under low light conditions, long exposures with
slow lenses will cause fast-moving auroras to blur, so it’s
generally better to use lenses with focal ratios of f/2.8 or
faster. One of the best lenses for shooting the northern
lights is an ultra-wide-angle lens that covers 100°° of sky
or more, enabling you to capture sweeping auroral arcs in
a single shot. A 10-mm f/2.8 fisheye lens is great for cam-
eras with APS-sized sensors, while full-frame cameras
perform best with a 15-mm f/2.8 fisheye lens.
During geomagnetic storms that produce extremely
bright auroras shimmering all across the sky, only circu-
lar fisheye lenses, such as an 8-mm fisheye, can record
the entire sky in a single frame. Although these lenses are
photographically slow with apertures of f/3.5 or greater,
their huge fields of view and small image scale allows you
to take long exposures with minimal blurring.
Make sure to bring at least two memory cards per
camera. Cheap memory cards tend to malfunction in
cold temperatures, so having a backup can often save an
otherwise wasted evening.
Avoid using most photographic filters when shooting
auroras. Ultraviolet- or infrared-blocking filters that are
excellent for daylight photography and for protecting the
lens surface can produce unattractive banding in aurora
photographs because they block some of the wavelengths
that auroras emit. This banding is difficult to remove
in post-processing. In the cold temperatures of high
latitudes where auroras are frequently seen, frost also
forms on filters more quickly than on an exposed lens
element. Even in warm temperatures and humid condi-
tions, condensation on your lens is a common problem

Top: Interesting foreground objects, such as this thin stand of

trees, can help create a more interesting composition. Bottom:
A tall, sturdy tripod enables you to quickly compose your images
without having to crouch in uncomfortable positions.

72 March 2013 sky & telescope

when temperatures rapidly fall. A fresh pack of lens cloths Strong auroral displays can change shape and brightness
is helpful under such conditions. Dew heaters made for within seconds, so having a fast, wide-angle lens is impor-
telescopes are also useful in holding off frost or dew, but tant to freeze the motion using short exposures. The author
they require an additional power source. recorded these two images only 30 seconds apart using a
In the cold nighttime temperatures of northern Canon EOS 5D DSLR at ISO 1600 and an 8-mm f/4 fisheye lens.
latitudes, spare batteries or external power supplies are
a smart addition to your gear, because cold temperatures than 30 seconds. You can record bright auroral displays,
significantly reduce battery life. Keep your extra batteries however, with the longer timed exposures available on
warm in your pocket, to help them maintain their charge. even the simplest camera models.
Older DSLR cameras often use more power than newer I strongly recommend bringing a sturdy tripod. Even
models, and they can drain batteries after only a few if it’s heavy and awkward to transport, it will reward you
dozen shots in extremely cold conditions. Newer models by helping you avoid the blurry images with wiggly stars
are often more power-efficient and will function for sev- caused by your camera shaking in windy conditions.
eral hundred to roughly 1,000 exposures even at extreme When shooting auroras with a picturesque landscape, a
temperatures, so having at least one spare set of batteries tall tripod also enables you to compose your shot without
is usually sufficient for a night of photography. When having to contort to see through your camera’s view-
shooting time-lapse photos, a battery grip or a larger finder. Ball-head accessories are also lighter than the
external battery may be best to avoid the gaps caused in a standard three-axis tripod heads and allow you to frame
series of exposures when you swap out a depleted battery. your composition quickly.
Chemical hand warmers are also an excellent accessory. When imaging the horizon at night, it’s often difficult
You can use them to warm your fingers and extra batter- to judge if the camera is level with the horizon, so a small
ies, but also your equipment: they can easily be affi xed to bubble level is also a helpful accessory.
your camera’s battery compartment to extend its life. Just like other types of astrophotography, the best loca-
A shutter-release cable is an essential accessory for tions are usually far from civilization. Consider bringing
aurora photography. Programmable models are useful along a friend for safety, or make sure someone knows
for time-lapse imaging or when taking exposures longer where you’re going. If you travel alone, bring some form

Sk yandTelescope.com March 2013 73

 Aurora Photography

of predator repellent, such as sprays or ultrasonic devices.

Wild animals usually avoid human contact, but you
should minimize the risk of dangerous encounters.

Destination: North
When heading out on an aurora expedition, it’s important
to know where to go for the best chance of witnessing a
display. A popular misconception is that the northern
lights appear strongest right at the geomagnetic pole. In
reality, auroras usually occur in a giant ring roughly 4,000
kilometers (2,500 miles) wide that surrounds each of the
geomagnetic poles. At the center of this oval, auroras
become less frequent and appear over the southern hori-
zon, such as in northern Alaska and Canada.
Although powerful geomagnetic storms can occasion-
ally produce auroras at temperate latitudes, these are rare.
So your best bet is to plan a trip to a location known for
frequent displays, such as Iceland, Alaska, and the Scan-
dinavian Peninsula.
Whether you live in a location that experiences frequent
auroral displays or prefer to wait for a strong geomagnetic
display to push the auroral oval down to your latitude, you
can monitor solar activity to know the best time to head
out to shoot. Some websites, including spaceweather.com,
track worldwide measurements of geomagnetic activity

Left: Although aurora photographers generally travel far from

urban locations to capture their best photographs, small settle-
ments, such as this settlement near Kiruna, Sweden, can enhance
your compositions. Below: From far northern regions such as
northern Alaska, Canada, and the Scandinavian Peninsula, aurora
often appear in the southern sky. The author recorded this photo
from northern Sweden, where the brightest arc of activity crosses
the southern constellation Orion, visible at right.

74 March 2013 sky & telescope

 the northeastern horizon. These bright displays are best
captured with short exposures of roughly 10 seconds at
an ISO of 800, in order to “freeze” any motion. Fainter
displays may require higher ISO speeds and longer expo-
sures of 30 seconds or more.
As with more general nightscape astrophotography
(S&T: November 2012, page 71), spend some time compos-
ing your foreground to ensure a good overall composition.
Avoid power lines, highways, and bright urban locations
if you want to achieve the best results.
The aurora has diverse colors, so setting your camera’s
color balance can be crucial to taking great photos. I often
select a custom white balance of around 4500–5500 kelvin
with my Canon EOS 5D to produce the most colorfully
diverse results that still look natural. You can also correct
the white balance in the post-processing of RAW files.
When shooting for an entire evening, I use two cam-
eras — one that I can move around to take varied com-
positions, and the other I leave stationary for the entire
Circular fisheye lenses enable you to shoot the entire sky in one evening to capture a time-lapse sequence that I can later
shot. These tend to be photographically slow, but their inher- assemble into a stunning movie using popular software
ently small image scale allows longer exposures than possible packages such as Startrails, StarStaX, AVIedit, or Adobe
with conventional lenses before blurring becomes objectionable. Photoshop (S&T: August 2009, page 66).
The unpredictability of auroras combined with their
with a scale known as the Kp index. This index ranges often rapidly-changing appearance make these polar
from 0, which is low activity, to 9, which means that a attractions a popular target for astrophotographers and
powerful geomagnetic storm is underway. An index of 5 or visual observers alike. By following this simple guide,
greater indicates a good chance of auroral activity at mid- you’ll be well on your way to taking world-class aurora
northern latitudes in the Western Hemisphere of roughly photos and movies! ✦
40° or higher. But at northerly latitudes of around 60°, such
as in northern Canada, a Kp index of 3 will produce bright Contributing photographer Babak A. Tafreshi is the founder
auroras visible at the zenith. of The World at Night (www.twanight.org) and is the 2009
Although intense geomagnetic storms are rare, the corecipient of the Lennart Nilsson Award for scientific photog-
most powerful tend to occur roughly once per solar cycle. raphy. See more of his nightscapes at www.dreamview.net.
The last one occurred in late October 2003, so we may be
due for one soon. You can learn more about the Kp index
and aurora predictions at the NOAA/Space Weather Pre-
diction Center: www.swpc.noaa.gov/Aurora.

Catching the Northern Lights

How to shoot the best aurora photos depends on how
strong the display is. But first, you need to focus your
camera. Set the lens focus at infinity and fine-tune the
focus using the camera’s Live View (if your camera
includes this feature), or take test exposures and zoom
in on a star to judge focus. Although sharp focusing is
not as critical as it is with telescopic imaging, it’s still an
important factor for capturing the best nightscape photos.
But remember that your subject is the sky, so don’t use
foreground objects as your focus point.
Once your camera is in focus, you can take a few test
exposures to see how short they can be while both ade-
quately recording the display and minimizing blur. From
an ideal location, auroras appear regularly in the form of
multiple bright arcs stretching from the northwestern to

Sk yandTelescope.com March 2013 75

Sean Walker Gallery showcases the finest astronomical images submitted to us by our readers. Send your
Gallery very best shots to gallery@SkyandTelescope.com. We pay $50 for each published photo. See
SkyandTelescope.com/aboutsky/guidelines.

▶ THE ANDROMEDA GAL A X Y

Terry Hancock
M31 presents numerous dust lanes and a bluish outer
halo punctuated by a ring of pinkish star-forming
regions in this enhanced-color photograph.
Details: TMB 92SS refractor with QHY9M CCD
camera. Total exposure was 22 hours through color and
hydrogen-alpha filters.

▾ PAC-MAN UNVEILED
Fabian Neyer
This extremely deep photo reveals the faintest outer
extremities of the molecular cloud NGC 281, the
Pac-Man Nebula, in Cassiopeia.
Details: Telescope Engineering Company APO140ED
refractor with SBIG STL-11000M CCD camera. Total
exposure was 30.8 hours through Baader Planetarium
color and hydrogen-alpha filters.

76 March 2013 sky & telescope

CORONAL STREAMERS
Robert B. & Elisabeth L. Slobins
The total solar eclipse of November 13–14, 2012,
featured wonderfully symmetrical streamers
such as those often seen during eclipses that
occur near solar maximum.
Details: Canon EOS 5D DSLR camera with 300-mm
lens. Composite of multiple exposures ranging from
½ 000 second to 1 second.

Sk yandTelescope.com March 2013 77

 Gallery

NEBULOUS WR AITH
Gerald Rhemann
The large bluish reflection nebula IC 4592 in
Scorpius is seen by some to resemble a horse
or dragon. It’s shown here with south up.
Details: 8-inch F/2.8 ASA astrograph with FLI
ProLine PL16803 CCD camera. Total exposure
was just over 2½ hours through FLI color filters.

78 March 2013 sky & telescope

 V
Visit SkyandTelescope.com/
gallery for more gallery online.
g

◀ DIAMOND RING
Koen van Gorp
The first glint of sunlight peeks out between lunar
mountains at the moment of third contact, marking
the end of totality as seen near Mount Carbine in
Queensland, Australia, on November 14, 2012.
Details: Canon EOS 40D DSLR camera with 300-mm
lens. Single exposure of ⅛ 000 second at f/5.6, ISO 100.

▾ TRIANGULUM PINWHEEL
Chris Cook
The face-on spiral galaxy M33 in Triangulum is noted
for its delicate spiral arms punctuated by numerous
pinkish knots of nebulosity.
Details: Astro-Physics 130EDFGT refractor with SBIG
ST-8300M CCD camera. Total exposure was 8⅔ hours
through Astrodon color filters. ✦

Sk yandTelescope.com March 2013 79

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84 March 2013 sky & telescope

 Index to Advertisers

Adorama . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Lunatico Astronomia . . . . . . . . . . . . . . . . . . 81

ADM Accessories . . . . . . . . . . . . . . . . . . . . . 81 Meade Instruments Corp. . . . . . . . . . . . .5, 88

Artemis CCD Ltd . . . . . . . . . . . . . . . . . . . . . . 81 National Park Service . . . . . . . . . . . . . . . . . . 15 SkyandTelescope.com

Ash Manufacturing Co., Inc. . . . . . . . . . . . . 69 Oberwerk Corp. . . . . . . . . . . . . . . . . . . . . . . . 81
800-253-0245
Astro Haven Enterprises. . . . . . . . . . . . . . . . 82
Observa-Dome Laboratories . . . . . . . . . . . . 59 IN THE NEXT ISSUE
Astro-Physics, Inc.. . . . . . . . . . . . . . . . . . . . . 83
Oceanside Photo & Telescope . . . . . . . . . . . 59
Astrodon Imaging . . . . . . . . . . . . . . . . . . . . . 81
Officina Stellare s.r.l. . . . . . . . . . . . . . . . . . . . 82
Astronomics . . . . . . . . . . . . . . . . . . . . . . . . . 15
Optic Wave Laboratories . . . . . . . . . . . . . . . 82
Bob’s Knobs . . . . . . . . . . . . . . . . . . . . . . . . . 81
Peterson Engineering Corp. . . . . . . . . . . . . . 81
Camera Bug Atlanta, Inc. . . . . . . . . . . . . . . . 66
PlaneWave Instruments . . . . . . . . . . . . . . . . 82
Celestron . . . . . . . . . . . . . . . . . . . . . .11, 17, 66
PreciseParts . . . . . . . . . . . . . . . . . . . . . . . . . . 80
CNC Parts Supply, Inc. . . . . . . . . . . . . . . . . . 80
Quantum Scientific Imaging, Inc. . . . . . . . . 25
David Chandler Company. . . . . . . . . . . . . . . 82

DiscMounts, Inc.. . . . . . . . . . . . . . . . . . . . . . 82 Rainbow Optics. . . . . . . . . . . . . . . . . . . . . . . 81

Santa Barbara Instrument Group . . . . . . . . . 3

Equatorial Platforms . . . . . . . . . . . . . . . . . . . 81 Caving on Other Worlds
Spacecraft have revealed caves on the
Explore Scientific - Bresser . . . . . . . . . . . . . . 25 ScopeStuff . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Moon and Mars, ideal habitats for
Finger Lakes Instrumentation, LLC . . . . . . . 13 Shelyak Instruments . . . . . . . . . . . . . . . . . . . 81 future human colonists.

Fishcamp Engineering . . . . . . . . . . . . . . . . . 82 Sky & Telescope . . . . . . . . . . . . . .42, 59, 66, 69 Remembering

FLO-USA Inc. . . . . . . . . . . . . . . . . . . . . . . . . 83
Comet Kohoutek
Software Bisque. . . . . . . . . . . . . . . . . . . . . . . 87 Forty years ago astronomers predicted
Focus Scientific . . . . . . . . . . . . . . . . . . . . . . . 66 a “Comet of the Century,” but it didn’t
Southern Stars. . . . . . . . . . . . . . . . . . . . . . . . 15 turn out that way.
Foster Systems, LLC . . . . . . . . . . . . . . . . . . . 81
Starizona . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Imaging Messier Marathon
Glatter Instruments . . . . . . . . . . . . . . . . . . . 81 An astrophotog-
Technical Innovations . . . . . . . . . . . . . . .80, 82
rapher imaged
Goto USA, Inc. . . . . . . . . . . . . . . . . . . . . . . . . 7 all 109 Messier
Tele Vue Optics, Inc. . . . . . . . . . . . . . . . . . . . . 2
objects in a single
Hands On Optics . . . . . . . . . . . . . . . . . . . . . 83
BOTTOM: ALEX MCCONAHAY; TOP: NASA / JPL-CALTECH / GLEN CUSHING (USGS)

Teleskop-Service Ransburg GmbH . . . . . . . 80 night. You can too.

Hotech Corp. . . . . . . . . . . . . . . . . . . . . . . . . . 80
Texas Nautical Repair, Inc. . . . . . . . . . . . . . . 59 Top Ten
Hubble Optics Sales . . . . . . . . . . . . . . . . . . . 81 Neglected
iOptron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
The Observatory, Inc. . . . . . . . . . . . . . . .66, 83 Objects
A veteran deep-sky
The Teaching Company . . . . . . . . . . . . . . . . 41
Kalaplex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 observer describes his favorite under-
appreciated deep-sky wonders.
Khan Scope Centre . . . . . . . . . . . . . . . . .66, 83 University Optics, Inc. . . . . . . . . . . . . . . . . . 81

Kitt Peak National Observatory . . . . . . . . . . 69 Van Slyke Instruments . . . . . . . . . . . . . . . . . 80 On newsstands March 5th!
Knightware. . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Willmann-Bell, Inc. . . . . . . . . . . . . . . . . . . . . 81
Find us on
KW Telescope / Perceptor . . . . . . . . . . . . . . 66 Woodland Hills Telescopes . . . . . . . . . . . . . . 9 Facebook & Twitter
 Focal Point Steve Lewis

Hooked n the Heavens

After two decades, a DSLR camera rekindles the author’s passion for astronomy.

It started when I was in 8th grade. Robert Suder, took me under his wing. ably remember the magical moment that
My parents bought me a pair of 7×35 With his sponsorship and mentoring, first introduced you to amateur astronomy.
binoculars for my birthday. They intended I started an astronomy club. We visited Share your excitement with others, and
my targets to be terrestrial objects and NASA’s Johnson Space Center in Houston, if you’ve been away for awhile, look again
wildlife, but out of curiosity, I aimed at had a couple of star parties, and viewed at the dark skies that once inspired you.
the night sky instead. sunspots. Then life happened. I went to Don’t wait for the perfect opportunity; take
I remember seeing a bright “star” college, graduated, got a job, and started a the first opportunity. You’ll get hooked on
with four smaller “stars” nearby. I had no family. Life’s financial and time commit- the heavens again too! ✦
idea what I was seeing, but I knew it was ments kept me from returning to the dark
something special. My inspiring science skies . . . until now, two decades later. Steve Lewis started in amateur astronomy
teacher, Mr. Schmidt, advised me to start Last year I purchased a DSLR camera when he was 14. He went on to become an
a journal and draw what I saw. After and a sturdy tripod for family vacations English teacher and, following graduate
reviewing sketches, he told me it was Jupi- and events. Then it happened. I pointed school, now works in the space industry on
ter and its moons. I couldn’t believe that I the camera at the night sky and captured the Colorado Front Range.
could see the moons of Jupiter with inex- some Quadrantid meteors, and then
pensive binoculars in the light-polluted anything else I could shoot with short,
skies of Austin, Texas. I was hooked. unguided exposures. I was hooked again
The following summer I saved my and needed a telescope.
lawn-mowing money to buy my dream On a budget, I sought one with crisp
telescope. It was a depart- optics, basic tracking capability, and
ment store’s best model, a portability. I purchased a refurbished
90-mm refractor with 6-inch Schmidt-Cassegrain telescope with
low-quality lenses. I advanced coma-free optics. Despite its
spent countless nights relatively small aperture, it has brought a
camping in my back- completely new world within my reach —
yard, observing and taking even in my neighborhood’s light-polluted
notes. I remember the fi rst skies. Its portability and Go To functional-
time I saw Saturn in all of ity has ensured it gets plenty of use.
its ringed glory. I remem- I recently snapped my first picture
ber star-hopping for hours through my telescope of the Orion Nebula.
in freezing weather. But I was blown away when I saw the reds and
my resources were limited blues in my 30-second exposure. Now I
and I was never able to see can’t resist a clear night. I have captured
many deep-sky objects. several other deep-sky objects. I realize my
In high school my setup doesn’t yield the best astrophotogra-
chemistry teacher, Dr. phy, but it has revitalized my excitement
for exploring the heavens.
I keep looking back to those 7×35 binoc-
ulars of my youth. Many of you can prob-
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86 March 2013 sky & telescope

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