The Outer Planets

Gas Giants & Pluto Jupiter, Saturn, Uranus and Neptune They are much more massive than Earth Do not have solid surfaces Composed of Hydrogen and Helium Thick atmospheres from strong gravity. They all have many moons and rings Pluto is a dwarf planet.

Jupiter The largest and most massive planet.

Jupiter’s Atmosphere Thick atmosphere of hydrogen and helium Great Red Spot- a storm larger than Earth. Similar to a hurricane but this storm never gets weaker. It has been around since the mid-1600’s.

Jupiter’s Structure Core of rock and iron. Thick mantle of hydrogen and helium. Thick atmosphere.

Jupiter’s Moons Galileo discovered Jupiter’s 4 largest moons. They are all larger than Earth’s moon. Each moon is different. Jupiter has over 63 moons.

Saturn The second largest planet in the solar system. Thick atmosphere. Contains clouds and storms. Average density is less than water.

Saturn’s Rings Made of ice and rock. Each noticeable ring is made up of several thinner rings.

Saturn’s Moons Largest moon- Titan Has over 56 moons.

Uranus 4 times the diameter of Earth. Very cold. Blue-green color because there are traces of methane in the atmosphere. Surrounded by rings.

Discovery of Uranus Discovered in 1781 William Herschel proved Uranus was a planet.

Exploring Uranus Voyager 2 Discovered that the planet rotates at an angle of 90 degrees from the vertical. It rotates from top to bottom instead of side-to-side!

Uranus’s Moons 5 largest moons have icy, cratered surfaces. Lava flows At least 27 total moons

Neptune A cold, blue planet. Atmosphere contains visible clouds. Similar in size and color to Uranus.

Discovery of Neptune Discovered as a result of a mathematical prediction. They thought an unseen planet (Neptune) was affecting Uranus’s orbit.

Exploring Neptune Voyager 2 photographed a Great Dark Spot about the size of Earth. Probably a giant storm. Storm didn’t last long.

Neptune’s Moons There are at least 13 moons. Triton is the largest moon. Triton’s south pole is covered by nitrogen ice.

Pluto Solid surface. Much smaller and denser than the outer planets. Smaller than Earth’s moon! Has at least 3 moons.

Pluto’s orbit Very elliptical. Crosses Neptune’s orbit.

Dwarf Planets Round and orbits the sun like a planet. However, dwarf planets have not cleared out the neighborhood around its orbit.