Solar System

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Solar System

• Introduction

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The Solar System consists mostly of empty space!

• The Sun 1 M?
• The Nine Eight Planets (? 0.001 M?)
• Asteroids and Rocky Debris (Negligible mass)
• Comets (?)

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Planets in the Solar System come in
two varieties
TERRESTRIAL
and
JOVIAN
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Mars
TERRESTRIAL (Earth-like)
Mercury
Earth
Venus
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Terrestrial Planets

• Mercury, Venus, Earth Mars

• Rocky Densities 3 5 g/cm3

• Small Radii 0.4 1.0 R?

• Low Masses 0.06 1.0 M?

• Few moons

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Jupiter
Neptune
JOVIAN (Jupiter-like)
Uranus
Saturn
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Jovian Planets

• Jupiter, Saturn, Uranus Neptune

• Gaseous No definite surface, low densities
• 0.7 1.75 g/cm3

• Large 4 11 R?

• Massive 17 318 M?

• Numerous moons

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We might add a third type of planet -- Kuiper
Belt Objects
Two large examples are
2003 UB313, the 10th planet
Eris
Pluto
2006 Both Pluto and 2003 UB313 are now called
Dwarf Planets
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The Solar System also contains
Comets
Asteroids
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Characteristics of the Solar System
The Planets orbit in nearly the same plane
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The Planets orbit around the sun in the
Counterclockwise Direction
And the JOVIAN planets are found in the outer
solar system
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Any theory which claims to explain the origin of
the Solar system must account for these three
basic characteristics.
The Planets orbit in nearly the same plane The
Planets orbit around the sun in the
counterclockwise direction. The Jovian planets
are found in the outer solar system and the
Terrestrial planets are found in the inner
solar system.
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The Nebular Theory
The Solar System began as a rotating, contracting
cloud of interstellar gas
As the cloud contracted gravitationally, it also
flattened, due to centrifugal force.
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As the cloud contracted and flattened, the
protosun formed at the center. In the
protoplanetary disk, planetisimals formed.
Through the process of accretion, these built up
into larger and larger, and eventually
planet-sized bodies.
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Stages in this process have been observed around
other stars
HD 141569
Beta Pictoris
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Temperatures varied from very high values (a
few thousand Kelvin) in the inner protoplanetary
disk to very low values (10s of Kelvin) at the
outer edge.
This means that in the inner solar system, low
melting point materials (gases, ices volatiles)
were lost, leaving behind only rocky (
refractory) materials.
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Thus, rocky, high density planets (the
Terrestrial planets) formed in the inner solar
system. In the outer protoplanetary disk, where
temperatures were much lower, volatiles were
retained, leading to the formation of the
gas-giant (Jovian) planets. These giant planets
are made primarily of hydrogen. Finally, icy
bodies (comet nuclei) formed out at the
very fringes of the protoplanetary disk.
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This theory thus accounts for the three basic
characteristics of the solar system
The Planets orbit in nearly the same plane The
Planets orbit around the sun in the
counterclockwise direction. The Jovian planets
are found in the outer solar system and the
Terrestrial planets are found in the inner
solar system.