The Outer Planets

The four outer planets are

Jupiter, Saturn, Uranus, and Neptune

Outer planets are

much larger and more massive than Earth, and they do not have solid surfaces.

Outer planets are also known as

gas giants.

Like the sun, gas giants are composed mainly of

hydrogen and helium and likely have dense rocky cores.

The gas giants strong gravity keeps

the gas giant's gases from escaping, so they have thick atmospheres.

Much of the hydrogen and helium is actually in

liquid form because of the enormous pressure inside the planets.

Gas giants' outer layers are very cold because

of their great distance from the sun.

Temperatures greatly increase

within the planets.

All gas giants have

many moons and a set of rings.

A ring is

a thin disk of small particles of ice and rock.

Jupiter is the

largest and most massive planet (about 2.5 times that of all the other planets combined!)

The Great Red Spot on Jupiter is a

constant hurricane-like storm larger than Earth.

Jupiter has more than

60 moons, including Io, Europa, Ganymede, and Callisto.

Saturn is the

2nd largest planet with average density less than water.

Saturn's rings

are the most spectacular (visible) in the solar system; each travels in its own orbit.

Saturn has more than

40 moons, including Titan (larger than Mercury).

Tho' 4x the diameter of Earth, Uranus is

much smaller than Jupiter and Saturn; has at least 27 moons.

Uranus is twice as far from

the sun as Saturn, so is much colder.

Uranus's axis of rotation is

tilted at an angle of about 90 degrees from the vertical.

Neptune is a

cold, blue planet with at least 13 moons, whose atmosphere contains visible clouds.

Neptune's Great Dark Spot was a

giant storm (about the size of earth) in its atmosphere that comes and goes, possibly related to Neptune's shrinking size.

Neptune was discovered by

a mathematical prediction based on surprises in Uranus' orbit.

Pluto has a

solid surface, is much smaller and more dense that the outer planets, has three known moons, and has a very elliptical orbit.

Pluto has been reclassified as a

dwarf planet: round, orbits the sun, but has not cleared out the neighborhood around its orbit.