The solar system consists of the sun and objects that orbit it, including 8 planets. The sun contains over 99% of the mass of the solar system. The planets are divided into terrestrial planets like Earth that are rocky, and gas giants like Jupiter that are mostly made of hydrogen and helium. All planets orbit the sun in elliptical paths and rotate counter-clockwise. The nebular theory proposes that the solar system formed from a rotating cloud of gas and dust that collapsed into a disk, with the sun forming at the center.

1. The Solar System
Earth Science
1st Semester

2. • The sun is the central
hub of a rotating wheel
of planets, their moons,
and many other smaller
celestial objects, such as
comets and asteroids.
• The sun is estimated to
contain 99.85% of the
mass of our solar
system.
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3. • The planets traveling outwards from the sun are as
follows: Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus, and Neptune.
• Pluto is no longer considered a planet.
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4. • Due to the sun’s gravity, all planets move in an
elliptical orbit in the same direction around
the sun.
• The closer a planet is to the sun, the faster it
travels in its orbit.
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5. The Planets: An Overview
• The planets fall into two groups – the
terrestrial planets, and the Jovian planets.
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6. • The terrestrial
planets include
Mercury, Venus,
Earth, and Mars.
• They are relatively
small and rocky.
• Since they are closer
to the sun they are
also known as the
inner planets.
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7. • The Jovian planets
include Jupiter, Saturn,
Uranus, and Neptune.
• They are huge planets
made primarily of gas.
• Since they are further
from the sun, they are
known as outer planets.
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8. • Size is the most notable
difference between the
terrestrial and Jovian
planets.
• Density, chemical
makeup, and the rate
of rotation are other
ways in which the two
groups of planets differ.
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9. • The planets have
different densities
because of their
different chemical
compositions.
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10. The Interiors of the Planets
• The substances that make up the planets are divided
into three groups based on their melting points.
• Gases: Hydrogen and Helium – have melting points
near absolute zero (-273 °C or 0 kelvin)
• Rocks: made from compounds of silicates and metallic
iron, both of which have melting points above 700°C.

11. • Ices: Include ices made from compounds of
ammonia, methane, carbon dioxide, and
water.
• These particular ices have intermediate
melting points.

12. • Terrestrial planets are dense and consist
mostly of rocky and metallic substances.
• They have very little gas and ice.
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13. • The Jovian planets are less dense because they
contain:
• Large amounts of gases like hydrogen and
helium.
• Ices made from water, ammonia, and methane.
• The outer planets cores contain rocky and
metallic materials.

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15. The Atmospheres of the
Planets
• A planet’s ability to hold
onto an atmosphere
depends on its mass and
temperature.
• Small, relatively warm
planetary bodies, with
small surface gravity
cannot hold much gas.
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16. • Therefore, terrestrial
planets have very thin
atmospheres.
• Jovian planets however,
have very thick
atmospheres composed
of hydrogen, helium,
methane and ammonia.
• They are able to retain
thick atmospheres due
to their large mass, and
low temperatures.
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17. Formation of the Solar
System – Nebular Theory
• Nebula are clouds of
dust and gas in space.
• These thin, gaseous
clouds begin to rotate in
space and collapse in
upon themselves.
• As they continue to
contract, they begin to
spin faster.
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18. • According to the
nebular theory, the sun
and planets formed from
just such a rotating disk
of dust and gases.
• As the speed of rotation
increased, the center of
the disk began to flatten
out and increase in
temperature.
• The sun eventually
formed in this location.
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19. Planetesimals
• Planets began to grow as
solid bits of matter
began to collide and
clump together in a
process known as
accretion.
• The colliding matter
formed small irregularly
shaped bodies known as
planetesimals.
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20. • As the collisions
increased, the
planetesimals grew in
size, eventually growing
large enough to exert a
gravitational pull on
surrounding objects and
pull them in.
• In this fashion the
planetesimals added
more mass and grew
into true planets.
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21. • In the inner solar
system, only metals and
rocks with high melting
points and high densities
could remain.
• The sun is too hot for
materials with low
melting points to stay
solid.
• The sun does not attract
items with low
densities towards it.
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22. • Materials with low
melting points and low
densities (like gases)
would be forced into the
outer solar system due
to the sun’s heat and the
solar wind.
• In the outer solar
system, the colder
temperatures allowed
materials with low
melting points to form
up as ice.
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23. • The Jovian planets were
able to form from
accumulating solid bits
of matter but also from
large quantities of ice.
• Eventually, the Jovian
planets grew so large
that they were able to
attract even the lightest
gases like hydrogen and
helium.
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