A Detailed Tour of the

Solar System

Image Credit: NASA

Objectives of the Presentation:

ü Revisit the formation of the Solar System

ü Describe the members of the Solar System
ü Discuss the formation of the Moon
ü Identify lunar phases
ü Explain the occurrence of tide, eclipse and season
ü Conclude that Earth is a unique planet
 How did the Solar System Form?
The Nebular Hypothesis
A. The nebula was composed mostly of hydrogen and helium.

B. About 5 billion years ago, the nebula began to contract.

C. It assumed a flat, disk shape with the protosun (pre-Sun) at the center.

D. Inner planets begin to form from metallic and rocky clumps.

E. Larger outer planets began forming from fragments with a high percentage of ices.
The Story of Planet Building

Planets formed from the same protostellar material as the sun, still
found in the sun’s atmosphere.
Rocky planet material formed from clumping together of dust grains in
the protostellar cloud.

Mass of less than ~ 15 Earth Mass of more than ~ 15 Earth

masses: masses:

Planets can grow by gravitationally attracting

Planets can not grow by
material from the protostellar cloud
gravitational collapse

Earthlike planets Jovian planets (gas giants)

 Formation and Growth of Planetesimals
Planet formation starts with clumping together of
grains of solid matter: planetesimals

Planetesimals (few cm to km in size) collide to

form planets.

Planetesimal growth through

condensation and accretion.

Gravitational instabilities may have

helped in the growth of
planetesimals into protoplanets.
 The Growth of Protoplanets

Simplest form of planet growth:

Unchanged composition of accreted

matter over time
As rocks melted, heavier
elements sink to the center ®
differentiation
This also produces a
secondary atmosphere ®
outgassing
Improvement of this scenario: Gradual change of
grain composition due to cooling of nebula and
storing of heat from potential energy
Why Solar System?

• “Sol” is the Latin name of the Sun

• Solar System means “system of the Sun”
• This star system is constituted by the
ØSun;
Øeight (8) planets;
Ødwarf and
Øplanetary debris (asteroids, meteoroids,
comets).
The Sun

Ø The sun is a star, a hot

ball of glowing gases
at the heart of our
solar system.

-Mean radius: 109.2 x that of Earth’s

-Volume: 1,301,018.805 Earths
-Mass: 333,060.402 x Earth's
-Maximum Surface Temp: 5,500 °C

Image Credit: NASA

The Sun
Regions of the Sun

Ø Solar Interior
• Core
• Radiative zone
• Convection zone
Ø Photosphere (sunspots)
Ø Chromosphere
Ø Corona

Image Credit: NASA

The Planets

Ø The word “planet” means wanderer

Ø IAU(2006) defines planet as any celestial body that:
a. is in orbit around the sun;
b. has sufficient mass for its self-gravity to overcome rigid body
forces so that it assumes a hydrostatic equilibrium (nearly round
shape)
c. *has cleared the neighbourhood around its orbit
Ø The four innermost planets are called terrestrial (meaning ‘Earth-like’)
Ø The larger outer planets—Jupiter, Saturn, Uranus and Neptune—are known
as the gas giants or Jovian planets, because their outer layers are
composed of gases such as hydrogen and helium

*criterion which demoted Pluto

The Planets in Orbit
Terrestrial (Inner) Planets)
Inner Planets: Mercury

Ø The smallest planet--only

slightly larger than Earth's
Moon.
Ø The planet closest to the Sun
Ø The fastest revolving planet--
revolves around the sun
every 88 days
Ø Very little atmosphere
Ø Extreme temperature
variation
Inner Planets: Venus
Ø Hottest planet--World of
intense heat and volcanic
activity. Thick and toxic
atmosphere traps heat in a
runaway "greenhouse
effect”
Ø “Veiled” planet
Ø Earth’s twin sister--similar in
structure and size to Earth
Ø Spins slowly in the opposite
direction of most planets.
Inner Planets: Earth

Ø Presence of Water and

Life
Ø an Old English word,
which simply means the
ground: eor(th)e and ertha
Ø Oceans, Atmosphere and
Lithosphere
Ø Has one moon– Luna
Ø Tide, Seasons, Eclipse
Inner Planets: Mars

Ø The red planet

Øseasons, polar ice
caps, volcanoes,
canyons and
weather
ØThe next Earth
Inner Planets: Mars
Olympus Mons

Deimos

Phobos
Jovian (Outer) Planets
Outer Planets: Jupiter

Ø Biggest Planet
Ø Strongest surface
gravity
Ø Fastest rotation
Ø Most number of
moons
Outer Planets: Jupiter

Gaseous Atmosphere
of Hydrogen, Helium,
Carbon Dioxide, Methane

Liquid Hydrogen

Liquid Metallic Hydrogen

Rocky Core
(10-15 Earth Masses)
Outer Planets: Jupiter

Jupiter’s Turbulent Atmosphere

Outer Planets: Jupiter

Great Red Spot

Little Red Spot

Outer Planets: Jupiter

Largest
Moon in the
Solar System

Galilean Moons
Outer Planets: Saturn

Ø Elegant Planet—thousand beautiful ringlets made

of chunks of ice and rocks
Ø Density less than that of water
Outer Planets: Saturn
Ø made of billions of individual
particles of mostly water ice
which create waves
Ø spread over hundreds of
thousands of km, yet they are
extremely thin – perhaps only 10
m thick.

Ø In order of their discovery, the

order of the main rings outward
from Saturn is D, C, B, A, F, G and
E.
Cassini division
Outer Planets: Saturn

Enceladus

Mimas

Iapetus

Saturn’s Major Moons

Outer Planets: Uranus

Ø Topsy-turvy planet--
equator is nearly at
right angles to its orbit
Ø Twin in size to
Neptune
ØBlue-green color

Miranda
Outer Planets: Neptune

Ø Farthest planet from

the sun
Ø Great Dark Spot
Ø Windy planet
Ø Longest revolution
period (165 years)--
completed its first
orbit in 2011 since
its discovery in 1846 Triton
Planetary Data
Planetary Data: Radii
Planets Radius
Mercury 2438 km

Venus 6052 km
Earth 6378 km
Mars 3397 km
Jupiter 71492 km
Saturn 60268 km
Uranus 25 559 km
Neptune 24 764 km
Planetary Data: Radii
Planetary Data: Radii
Planetary Data: Mass
Planets Mass
Mercury 3.3x1023 kg

Venus 4.87x1024 kg
Earth 5.974x1024 kg
Mars 6.42x 1023 kg
Jupiter 1.90x1027 kg
Saturn 5.69x1026 kg
Uranus 8.69x1025 kg
Neptune 1.02x1026 kg
Planetary Data: Escape Velocity

Planets Escape velocity

Mercury 4.3km/s

Venus 10 km/s
Earth 11km/s
Mars 5.0 km/s
Jupiter 60 km/s
Saturn 39 km/s
Uranus 21km/s
Neptune 23 km/s
Escape velocity: the minimum velocity necessary to escape a planet’s gravitational attraction
Planetary Data: Rotational Period
Planets Rotational period
Mercury 59 days
Venus 243 days

Earth 1 day
Mars 24.6 hours
Jupiter 9.9 hours
Saturn 10.7 hours

Uranus 17.2 hours

Neptune 16.1 hours

Planetary Data: Rotational Period

*Rotation of any celestial body on its axis creates a day.

Planetary Data: Revolution Period

Planets Revolution period

Mercury 88 Earth days
Venus 225 Earth days
Earth 365.25 Earth days
Mars 687 Earth days
Jupiter 11.8 Earth years
Saturn 29.5 Earth years
Uranus 84 Earth years
Neptune 165 Earth years
Planetary Data: Revolution Period

*Revolution of any celestial body on its orbit creates a year.

Planetary Data: Surface Temperature

Planets Surface temperature

Mercury 400K
Venus 730K
Earth 280K
Mars 210K
Jupiter 125K
Saturn 25K

Uranus 60K
Neptune 60K
Planetary Data: Axial Tilt
Planetary Data: Surface Gravity
Planets Surface gravity
Mercury 0.38 g
Venus 0.91 g
Earth 1.0 g
Mars 0.38 g
Jupiter 2.54 g
Saturn 1.08 g
Uranus 0.91 g
Neptune 1.19 g
Planetary Data: Known Moons
Planets Known Moons
Mercury 0
Venus 0
Earth 1
Mars 2
Jupiter More than 50
Saturn 30
Uranus 21
Neptune 8
Dwarf Planets

Ø In 2006, Pluto, Eris and the

asteroid Ceres became the
first dwarf planets.

Ø They lack the gravitational

muscle to sweep up or
scatter objects near their
orbits and end up orbiting
the sun in zones of similar
objects such as the
asteroid and Kuiper belts.
Ø Other dwarf planets:
Ø Makemake, Haumea
Dwarf Planets
Planetary Debris

Comet

Asteroid

Meteorite
Planetary Debris: Asteroid

Ø Rocky, airless worlds that orbit our sun, but are too
small to be called planets.
Ø Size ranges from 1 km to 900 km
Ø Classified as either carbonaceous (C),
silicaceous (S) or metallic (M)
Ø The region called the asteroid belt or simply the
main belt, may contain millions of asteroids.
Ø Asteroids that pass close to Earth are called Near-
Earth Objects (NEOs).
Planetary Debris: Comet

Ø Short period (<200yrs) comets come

from the Kuiper Belt while long period (30
M yrs) comets come from the Oort Cloud
Ø The nucleus contains icy chunks and
frozen gases with bits of embedded rock
and dust and a small rocky core.
Ø A comet warms up as it nears the sun
and develops an atmosphere, or coma
Ø The pressure of sunlight and high-speed
solar particles (solar wind) blow the
coma materials away from the sun,
forming a long, and sometimes bright,
tail—made of dust and plasma.
Planetary Debris: Meteoroid

ØLittle chunks of rock and debris in space are

called meteoroids.
ØMeteoroids become meteors or shooting stars
when they fall through a planet's atmosphere
leaving a bright trail as they are heated to
incandescence by the friction of the atmosphere.
ØPieces that survive the journey and hit the
ground are called meteorites.
Planetary Debris: Meteoroid

Ø Meteoroids originate
from:
a. Interplanetary
debris of the asteroid
belt

b. fragments of
comets
References

Solar System Exploration

http://solarsystem.nasa.gov/planets/profile.cfm?Object=SolarSys

Planetary Data:
Fix, John D. Astronomy: Journey to the Cosmic Frontier. 3rd edition. McGraw-Hill
Publishing House Inc.2004.
Jones, Tony. Trends in Science: Astronomy. Helicon Publishing. UK; 2001.
Arny, Thomas T. Explorations: An Introduction to Astronomy. Mosby- Year Book,
Inc., 1996
Retrograde Motion

Ø “Retrograde" motion is the apparent backward

motion of a planet caused by its being lapped by
another planet, or vice-versa.
ØIn this "retrograde" motion, neither planet is
actually moving backwards; it only appears that
way, during the time that one laps the other.
Retrograde Motion
Mars Against Earth

*Both planets move in an eastward motion (prograde) around the Sun, but the
planet with the inside (smaller) orbit moves faster than the planet on the
outside (larger) orbit, and when it passes the slower-moving planet, each
sees the other one as apparently moving backwards relative to its usual
motion around the sky.
Luna—Earth’s only Moon: Facts

Ø as old as Earth according to

the Great Impact Theory
Ø dark, rocky world composed
mostly of iron, silicon and
aluminum
Ø gravity of 1/6th to that of
the Earth
Ø only about a quarter of the
Earth’s size
Ø several impact craters and
plains
Luna—Earth’s only Moon: Facts

Øexhibits
synchronous
rotation (equal
periods of rotation
and revolution)
Ø the farthest alien
world visited by
humans
Earth-Sun-Moon Relationship: Lunar Phases

Phase=shape=portion illuminated by the Sun

New Moon
First Quarter
Full Moon
Last Quarter
Earth-Sun-Moon Relationship: Lunar Phases

Note:
The position of
the Moon
relative to the
Earth and the
Sun causes its
changing
phases.
Earth-Sun-Moon Relationship: Lunar Phases

Note:

Waxing means growing

Waning means shrinking
Gibbous means swollen on one side

*It takes 29.53 days for the Moon to complete

one cycle
Earth-Sun-Moon Relationship: Lunar Phases

The 8 Phases

1. New Moon
2. Waxing Crescent
3. First Quarter
4. Waxing Gibbous
5. Full Moon
6. Waning Gibbous
7. Last Quarter
8. Waning Crescent
Earth-Sun-Moon Relationship: Lunar Phases

Consider this position of celestial bodies:

Earth-Sun-Moon Relationship: Lunar Phases

First Quarter
Earth-Sun-Moon Relationship: Lunar Phases

New Moon
Earth-Sun-Moon Relationship: Lunar Phases

Waxing Crescent
Earth-Sun-Moon Relationship: Lunar Phases

Waxing Gibbous
Earth-Sun-Moon Relationship: Lunar Phases

Full Moon
Earth-Sun-Moon Relationship: Lunar Phases

Waning Gibbous
Earth-Sun-Moon Relationship: Lunar Phases

Waning Crescent
Earth-Sun-Moon Relationship: Lunar Phases

Last Quarter
Earth-Sun-Moon Relationship: Tides

Ø Tides refer to the daily

changes in the
elevation of the ocean
surface.
Ø Ocean tides result from
the gravitational
attraction exerted upon
Earth by the moon and,
to a lesser extent, by
the Sun.
Earth-Sun-Moon Relationship: Tides

Spring Tide
Neap Tide

Ø Spring tides are strong tides that occur when the

Earth-Sun-Moon are in a straight line.
Ø Neap tides occur when the three bodies form a
right angle.
Earth-Sun-Moon Relationship: Eclipse

Ø Eclipse happens when one celestial body

casts a shadow over the other
ØDuring a new moon or full-moon phase, the
moon’s orbit must cross the plane of the
ecliptic for an eclipse to take place.
Earth-Sun-Moon Relationship: Eclipse

Ø Solar eclipses occur when the moon moves in a

line directly between Earth and the sun, casting a
shadow on Earth.
Earth-Sun-Moon Relationship: Eclipse

Ø Lunar eclipses occur when the moon passes

through Earth’s shadow.
Earth-Sun Relationship: Season

Ø Season (winter, spring,

summer or fall) is a
consequence of
Earth’s axial tilt and the
length of daylight is
caused by Earth’s
changing position
relative to the sun in
any point of its orbit.
Earth’s axis is tilted at 23.5°
Earth-Sun Relationship: Season

Ø Solstice means Spring/Vernal

unequal length of Equinox

daytime and night

time.
Ø Equinox means
equal duration of
day and night. Autumnal(Fall)