The Outer Planets

The Inner Planets to Scale

3,031 mi 7,521 mi 7,926 mi 4,222 mi

5.4 g/cm3 5.2 g/cm3 5.5 g/cm3 3.9 g/cm^3

The Outer Planets to Scale

88,700 mi 75,000 mi 31,700 mi 30,200 mi1.3 g/cm3 0.7 g/cm3 1.3 g/cm3 1.6 g/cm3

Outer Planet Similarities

• All are tens of thousands of miles across– Much larger than the inner planets

• All are made of gas - hydrogen and helium– No rocky surface like the inner planets

• All are not very dense (b/c made of gas)• Why do the outer planets share these

similarities?• Why don’t the outer planets have more in

common with the inner planets?

Jupiter

• Largest planet• Colorful cloud bands• Rapid rotation

(9h50m)• -250°F at cloud tops• Great Red Spot

Great Red Spot• Hurricane-like storm,

fueled by heat inside of Jupiter

• Large enough to cover 3 Earths

• Discovered by Galileo nearly 400 years ago– Why can it last so long

compared with hurricanes on the Earth?

Saturn

• Least dense planet - Would float on water!

• Bulges because of rapid rotation (10h30m)

• Large, broad rings

Saturn’s Rings

• Made of countless small chunks of ice and rock– Why don’t the chunks

combine to form a moon?

– Why doesn’t Earth have rings?

• 170,000 miles wide, <1 mile thick

Uranus• Discovered by

accident (1781)• Blue-green color from

methane in its atmosphere

• -350°F at cloud tops• Almost featureless;

little weather– Why might Uranus

lack distinctive weather patterns?

Uranus’ Axis

• Axis tilted 98° from its orbit• Orbits Sun every 84y• How would these factors affect its seasons?

What’s Wrong with Uranus?

• Following its discovery, astronomers calculated its orbit

• Uranus mysteriously speeded up, then slowed down– Why might Uranus

have deviated from its calculated orbit?

Neptune• Discovered at its

predicted position (1846)

• Blue color from methane• -370°F at cloud tops• Great Dark Spot in

1989, but not 1994– How is this different from

the Great Red Spot?– Why is its weather

different from Uranus? Jupiter?

The S.S. Family Portait