Download Ch. 3 Sec. 4 Notes

Ch. 3 Sec. 4 Notes
The Outer Planets
*Jupiter, Saturn, Uranus, and Neptune are the 4 outer planets
Gas Giants and Pluto
*The 4 outer planets are much bigger than Earth and do not have solid surfaces
-Referred to as gas giants
-Pluto is a "gas dwarf"
*The gas giants are composed of mainly hydrogen and helium
*Due to their large size, their gravity is much stronger and can hold in all the gas
-Provides a thick atmosphere
*Even though they are called gas giants, all the gas is mainly in liquid form because
of the enormous pressure inside the planets
*The outer layer of the gas giants is extremely cold because of their great distance
from the sun
-Temperatures increase as you go inside the planet
*All the gas giants have many moons
*Each gas giant is surrounded by a set of rings
-Thin disk of small particles of ice and rock
Jupiter
*Largest and most massive planet
*Mass is still 2.5 times greater than all the other planets combined
*1,300 Earth's can fit inside Jupiter
Jupiter's Atmosphere
*Thick atmosphere of hydrogen and helium
*Has a Great Red Spot, a storm that is larger than Earth
-Similar to a hurricane that hasn't stopped since the 1600s
Jupiter's Structure
*Has dense core of rock and iron at the center (only place that is solid)
*A thick, liquid mantle of hydrogen and helium
*The air pressure of Jupiter's core is 30 million times greater than at Earth's core
Jupiter's Moons
*Galileo discovered the 4 largest moons of Jupiter
-Io, Europa, Ganymede, and Callisto
-Larger than Earth's moon
*Scientists have discovered dozens of other smaller moons orbiting Jupiter within
the last couple of decades
Saturn
*Second largest planet in solar system
*Voyager is the probe that showed Saturn also has a thick atmosphere made up of
hydrogen and helium
*Saturn is the only planet whose average density is less than that of water
Saturn's Rings
*Made of chunks of ice and rock, traveling in its own orbit around Saturn
*Saturn's rings are the most spectacular rings of any planet because it looks like a
giant CD circling the planet
Saturn's Moons
*Saturn's largest moon, Titan, is larger than the planet Mercury
*Titan was discovered in 1665
-Atmosphere is so thick, that little light can go through it
*There are 4 other moons that orbit Saturn and are all over 1,000 km in diameter
Uranus
*Looks blue-green because of traces of methane in the atmosphere
Discovery of Uranus
*In 1781, Uranus became the first new planet discovered since ancient times
*An English astronomer named William Herschel discovered a fuzzy spot in the sky
and started the era of active solar system study
Exploring Uranus
*Voyager 2 arrived at Uranus in the 1980s
*Images showed a few clouds, but scientists discovered that Uranus rotates in 17
hours
*Uranus's axis of rotation is tilted 90 degrees from the vertical
*Like Venus, scientists believe a big object hit and knocked it on its side
Uranus's Moon
*Uranus's 5 largest moons have icy, cratered surfaces
*Have evidence of lava that erupted out from within each moon
*Uranus has a total of 27 moons
Neptune
*Cold, blue planet
*Atmosphere contains visible clouds
*Scientists think Neptune is shrinking, causing its interior to heat up
*As the heat rises, it produces clouds and storms
Discovery of Neptune
*Neptune was discovered as a result of a mathematical prediction
*Astronomer's hypothesized that the gravity of an unseen planet was affecting
Uranus's orbit
*By 1846, the unseen planet's orbit was calculated
* A few years later, an unknown object was spotted in the sky = Neptune
Neptune's Moons
*At least 13 moons orbiting Neptune
*The largest moon is Triton, which has a thin atmosphere
-South pole is covered in nitrogen ice
Pluto
*Pluto DOES have a solid surface and is much smaller and denser than the other
planets
-Smaller than Earth's moon
*Pluto has 3 known moons
Pluto's Orbit
*Pluto is so far away that its 1-year is equivalent to 248 Earth years
*Its orbit is extremely elliptical
Dwarf Planets
*Scientists discovered two other bodies of mass that are very similar to Pluto in the
last couple of years
*They have decided to take Pluto out as the 9th planet of our solar system and
make a new class of planets
-Called "dwarf planets"
*Dwarf planets are round and orbit the sun, but run into other objects when it
orbits the sun