The Gas Giants The Planets and Other Cosmic Stuff Chapter 20

Jovian Planets Are called “Jovian” which means “ Jupiter-like ” or outer planets Are made completely of gas held together by gravity Are the largest of all the planets in the solar system All have numerous moons and thin atmospheres

Jupiter Largest of all the Jovian planets Composed mainly of H and He with a partially liquid atmosphere Clouds are made of water, methane, and ammonia Most noticeable feature is the Great Red Spot Its mass is 318 times that of the Earth As of 2004, Jupiter has 63 moons, with the largest being Io, Europa, Ganymede, and Callisto

Saturn Composition is very similar to Jupiter, mostly hydrogen and helium Most noticeable feature are the rings made of pieces of ice Has 34 moons, with the largest being Titan Titan is the only moon known to have an atmosphere

Uranus Discovered by William Herschel in 1781 Because of the high amounts of methane, Uranus is a greenish-blue Its axis is tilted nearly parallel to its orbital plane, rotating like a wheel! Has only been visited by Voyager 2 in 1986 Has a few very faint rings Uranus has 21 moons, with the largest being Miranda, Ariel, Oberon, Umbriel, and Titania

Neptune Atmosphere is very similar to Uranus, in which the methane gives it its bluish color Voyager 2 took pictures of the Great Dark Spot, which is similar to the Great Red Spot on Jupiter Even though it is the 8 th planet, sometimes Pluto crosses its orbit, making it the 9 th planet Has 13 moons, with Triton being the largest

Pluto, Our Dwarf Planet The term “dwarf planet” was coined in August 2006, which means that it IS a planet, but it has not cleared its neighborhood around its orbit like the other 8 do Pluto’s orbit passes through the Kupier Belt, an area beyond Neptune where comets are thought to be born. The other 8 do not pass through the Kupier Belt Has a moon, Charon Pluto Charon

Comets Sometimes referred to as “ dirty snowballs ” because they are made of loosely packed ice and rock Orbits are VERY elliptical When it passes close to the Sun, the ice melts and creates the characteristic “tail” which points away from the Sun Thought to originate from the Kupier Belt or Oort Cloud found way beyond Neptune Most famous is Halley’s Comet, which comes closest to the Sun every 76 years…be looking in ! Coma Gas Tail Dust Tail

Meteoroids, Meteors, & Meteorites What’s the difference? 1.Meteoroids are small rocky bodies orbiting the Sun which are smaller than asteroids 2.Meteors are meteoroids that enter our atmosphere and burn up in spectacular meteor showers 3.Meteorites strike the Earth’s surface Three types: stony, metallic, and stony-iron Leonid meteor shower

Asteroids Small, rocky bodies in orbit around the Sun, ranging in size from a few meters to more than 900 km in diameter Largest area of asteroids is between Mars and Jupiter, called the Asteroid Belt Have a variety of compositions The large ones have been named Ida Gaspra