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Earth Science Class Notes
Topic: Planets of the Solar System
Name:
Date: September 19, 2011
Chapter 27 , Section # 1 & 3:
Period: 4
Questions / Main Ideas /
Vocabulary
Section 1 Intro
Key Terms:
solar system
planet
solar nebula
planetesimal
Notes / Answers / Definitions / Examples / Sentences
The Solar System is made up of the sun, planets and all other bodies of mass
that orbit the sun. Planets are known to be the main bodies that orbit (go around) the
sun. In 1976 the nebular hypothesis was created by a French mathematician. This
hypothesis states that both the sun and planets were created simultaneously from a solar
nebula. After the Big Bang, matter was spread throughout the universe. Some made
group up into clouds of dust and gas. In the center of the nebula, the sun is said to have
formed through nuclear fusion. The sun is made up of 99% of the matter that was once
in the solar nebula.
Formation of Planets
While the sun was forming, so were the planets in the outer regions. Planetesimals are
smaller bodies of mass that planets came from. Some planetesimals crashed together to
form protoplanets. Protoplanets’ gravity caused planetesimals to collide with them
forming more massive protoplanets. This later formed denser planets and moons. Moons
are smaller bodies that orbit the planets
Section 3-The Inner Planets
Inner planets (also called terrestrial planets) are the closer ones to the sun. They include:
Key terms:
Mercury, Venus, Earth and Mars. They are made up of mostly solid rock and metallic
terrestrial planet
cores.
Mercury: Closet to the sun
It circles the sun every 88 days. It rotates on its axis every 59 days. The temperature
ranges from 801 degrees F to -343 degrees F.
Venus: Second from sun
It circles the sun every 225 days. It slowly rotates on its axis every 243 days. It is
considered Earth’s twin due to the being almost the same size, mass and density.
Venus’ atmosphere is made up of CO2 (carbon dioxide) making the temperature go as
high as 867 degrees F. This is known as the runaway greenhouse effect. It also has
sulfur dioxide droplets that create cloud layers that reflects sunlight. In 1970 six probes
were sent to Venus and found rocks made of granite and basalt. The same as that on
Earth!!
Earth: Third from sun
It orbits every 365 ¼ days. It rotates completely on its axis every 24 hours. It also has a
large moon. Its distance from the sun allows water to exist in a liquid state allowing it to
dissolve carbon dioxide in the atmosphere.
Mars: Fourth from sun
It orbits the sun every 687 days. It rotates on its axis every 24 hours and 37 minutes.
Mars tilts the same as Earth and allows it to have seasons also. They have volcanoes;
however they have not been activated because Mars does not have moving tectonic
plates as Earth does. It is believe that water once exited on Mars in a liquid state due to
erosion.
Section 4: The Outer Planets
Key terms:
gas giants
Kuiper Belt
The four planets farthest from the sun are known as the outer planets. An Asteroid belt
separates them from the planets. These four outer (or gas planets) are Jupiter, Saturn,
Uranus, and Neptune. These are much larger than the closer four, but are less dense.
There gases are mostly made up of helium and hydrogen.
Jupiter: Fifth from sun
This is the largest planet in the Solar System. It takes Jupiter 12 years to orbit the sun. It
rotates on its axis faster than any other planet. It only take 9 hours and 50 minutes. It has
60 moons and several small rings. Hydrogen and helium make up 92% of its atmosphere.
The average temperatures is -320 degrees F. This planet has Great Red Spots that build
up due to rotating storms. Inside the planets of Jupiter, temperatures are 54,032 degrees F
and causes its interior to be liquid metallic hydrogen.
Saturn: Sixth from sun
It orbits the sun every 29.5 years. Due to its distance from the sun, it is very cold and has
a temperature of -349 degrees F. It has 47 moons. It is made of hydrogen and helium
with a rocky iron core. It is the least dense planet in the solar system. It is known for its’
rings.
Uranus: Seventh from sun
Third largest planet in the solar system. It takes 84 years to orbit the sun. It has 24 moons
and at least 11 thing rings. It spins on its axis on the side. It contains hydrogen, helium
and methane that gives it the bluish color. Its core’s temperature is 12,632 degrees F.
Neptune: Eighth from sun
It takes 164 years for it to orbit the sun. It rotates on its axis every 16 hours. Neptune’s
average temperature is -437 degrees F.
Objects Beyond Neptune
Pluto was known as the 9th planet until2006. Today, we know of it as a dwarf planet. It
is smaller than Earth’s moon. Scientists suggest that frozen methane and rock make up
this dwarf planet. Pluto’s temperature is -423 degrees F.
Kuiper-Belt
What makes an object a planet
This is the region just beyond Neptune’s orbit
1. Must revolve around the sun
2. Must be round due to its own gravitational pull
3. Has to have cleared all the objects around it orbital path