Pluto, the only planet to be discovered by an American, is again facing a
fateful vote on whether it will continue to be listed among the planets of our solar system, or relegated to a big ball of dirty ice.
The issue has come up before, and Pluto has won out several times. The last by a tie going to the planet. This week, the International Astronomical Union will meet in Prague for it's 12-day
General Assembly. A proposed definition of "planet" is due to be released tomorrow and voted on next week. (In the photo, that's Pluto in the foreground; slightly below and to your right is its moon, Charon.)
NPR claims to have inside information that Pluto will be permitted to retain its planetary designation, but the definition would result in other objects being added to the planetary classification.
Others aren't so sure.
I hope NPR is at least partially correct -- Pluto deserves to remain in the class of planets, even if only for historical purposes. I've actually seen the little guy with my own eye and, knowing the history of the discovery, it is something worth keeping around.
Clyde Tombaugh was born in 1906, in Illinois. Soon after, his family moved to Burdett, Kansas (
2000 pop - 256 souls). There, as he grew up, he became interested in astronomy. He taught himself the subject and, as the family could not afford even the most meager of telescopes, he taught himself how to make them. He ground the glass for his lenses in the root cellar. After a hard day in the fields, Clyde spent many late nights back out in the fields, with his home-made telescopes, investigating the heavens. As a boy, he dreamed of discovering a new planet the way some of us dreamed of hitting the game-winning homer in the bottom of the ninth in Game 7 at The Stadium.
He built a couple of dozen telescopes as a teenager and in the late 1920s completed work on a very precise 23-centimeter reflector telescope. He used the crankshaft from a 1910 Buick and old parts from a cream separator for his mount. With this telescope he made some close observations of the planets and highly detailed sketches. He sent his drawings and data to the
Lowell Observatory, hoping to get some helpful suggestions. Instead, he received a job offer. He was to help in the search for the theorized
Planet X. Within a year, at age 24, he discovered Pluto. After
that, he went to college and onto a distinguished career in astronomy.
At the time, Pluto was believed to be about 500 times the mass of the Earth. Today, it is estimated to be smaller than the moon. The planet was named Pluto at the suggestion of a girl in England, whose father wired the suggestion to the Lowell Observatory. They adopted the name because Pluto was the god of the underworld, which they thought apt for such a remote, dark and cold place, and because the first two letters -- PL -- were the initials of Percival Lowell, who had theorized Planet X and started the private observatory bearing his name, in which the planet was finally discovered 15 years after his death.
Today NASA's
New Horizons spacecraft is on a mission to Pluto, expected to rendezvous in 2015. On board, tucked amid the cameras and scientific instruments, are
Clyde Tombaugh's ashes. It is only fitting that Pluto still be a planet when he gets there.
UPDATE (8/15/06): Tom Gehrels, an asteroid expert from the University of Arizona, is leading the charge to preserve Pluto's status as the ninth planet in the solar system and to desginate
Xena as the tenth. In a front-page article in today's
Dissertatio -- the IAU conference's daily newspaper -- Gehrels offers the following proposal:
The regular asteroid observers, including amateur astronomers, are doing well with their CCDs in faint follow-up astrometry. However, large wide-angle telescopes and special equipment are needed to explore the outer solar system, including the rare objects that might qualify as planets. The searching is done with expensive telescopes by experts who are not always asteroid observers. The greatest encouragement for exploration of the outer solar system is the excitement that a new Planet might be found. Observatory directors and funding agencies are well aware of that.
This proposal is therefore to stay with the 75 years of popularly considering Pluto the Ninth, as the IAU agreed to in Manchester, and to adopt Xena as the Tenth Planet because it is intrinsically brighter than Pluto. The proposal is further that the same accurate and convenient criterion be used for naming an Eleventh Planet and so forth, namely that they be intrinsically brighter than Pluto, measured in “absolute V-magnitude.” Pluto's absolute visual magnitude is –0.76, Xena's –1.2. The present proposal is written on behalf of people who are doing the observing and discovering, who see the need for prompt recognition and the fastest return in naming. This has been explained before, in Nature 436, 1088, 2005 and Sky & Tel. 111, No. 1, 14, 2006, and this Letter has been circulated in draft form, but there has been no response from the two naming committees of the IAU. Considering roundness due to gravitational stability is complex, time consuming, subject to change, and impossible due to faintness at great distance.
A compromise for proper study and distinction of the various objects and populations is to attach to Pluto and to any new Planets also the usual comet or asteroid designation. Xena already has 2003 UB313, which eventually will be a 6-digit catalog number. The dual assignment, as Planet and comet or asteroid, will also stimulate discussion in schools and colleges of the rich variety of solar-system objects.