The Outer Planetsp. 575

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 mi

1.3 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– Call GAS GIANTS– All have many moons and is surrounded by

rings

• 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 and most

massive planet• Its mass is 2 ½ times all the

planets combined.• Colorful cloud bands• Thick atmosphere of

hydrogen and helium• Rapid rotation (9h50m)• -250°F at cloud tops• Pressure at core is approx.

30 million X greater than earth’s pressure.

• Has 63+ moons (Io, Europa, Ganymede, and Callisto

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? No land to weaken it.

Saturn

• Least dense planet - Would float on water!

• 2nd largest planet• Atmosphere is

hydrogen and helium• Bulges because of

rapid rotation (10h30m)

• Large, broad rings

Saturn’s Rings• Made of countless small

chunks of ice and rock each travelling its own orbit around Saturn.– Why don’t the chunks

combine to form a moon?– Why doesn’t Earth have

rings?

• 170,000 miles wide, <1 mile thick

• Largest moon-Titan is larger than Mercury

• Has 60+ moons

Uranus• Discovered by accident

(1781)• Blue-green color from

methane in its atmosphere• 4X diameter of earth• Could hold 1300 Earths• Thick atmosphere of

hydrogen and helium.• -350°F at cloud tops• Twice as far from sun as

Saturn.• Almost featureless; little

weather– Why might Uranus lack

distinctive weather patterns?

Uranus’ Axis• Axis tilted 98° from its orbit (rotates top to

bottom)• Orbits Sun every 84y• How would these factors affect its seasons?• At least 27 moons

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)

• At least 13 moons• 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

• http://www.youtube.com/watch?v=HEheh1BH34Q

• www.brainpop.com – jupiter, saturn, uranus, neptune, outer solar system

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