outer planets![click to hear](/images/speaker.jpg)
Planets located beyond the asteroid belt; these are known as the gas giants.
50 astronomical units ![click to hear](/images/speaker.jpg)
Corresponds to about 50 times the Earth-Sun distance.
Uranus ![click to hear](/images/speaker.jpg)
Seventh planet from the Sun, also the third largest planet; Uranus is composed mainly of rock, ice and hydrogen and features 11 rings.
Neptune ![click to hear](/images/speaker.jpg)
Eighth planet from the Sun; its atmosphere, composed of hydrogen, helium and methane, gives Neptune its bluish color. Features four rings.
Kuiper belt ![click to hear](/images/speaker.jpg)
Circular region of the solar system about 50 astronomical units from the Sun; thought to be a repository of small icy bodies, the source of comets.
Pluto ![click to hear](/images/speaker.jpg)
Discovered in 1930, it was long considered the ninth planet of the solar system. Since 2008, it has been classified as a plutoid.
Saturn ![click to hear](/images/speaker.jpg)
Sixth planet from the Sun, also the second largest planet; Saturn is encircled by rings forming a band about 120,000 mi in diameter.
Jupiter ![click to hear](/images/speaker.jpg)
Fifth planet from the Sun, also the largest; Jupiter is 1,330 times the size of Earth.
Sun ![click to hear](/images/speaker.jpg)
Star around which the planets gravitate; represents over 99.8% of the total mass of the solar system.
Oort cloud ![click to hear](/images/speaker.jpg)
Region of space bordering the solar system about 50,000 astronomical units from the Sun; composed of billions of comets.
50,000 astronomical units ![click to hear](/images/speaker.jpg)
Corresponds to about 50,000 times the Earth-Sun distance.