Question

What are the gas planets known as?

The gas planets are the Jupiter-like planets that are composed of primarily hydrogen and helium. These planets, Jupiter, Saturn, Uranus, and Neptune, are located farther from the sun than the terrestrial bodies, Mercury, Venus, Earth, and Mars--they are also much more massive. Jupiter, the largest of all planets in the solar system, is 300 times more massive than Earth and its diameter is about 10 times larger. However, the “gas giants” are composed of lighter elements, so overall their density is much less than rocky (terrestrial) planetary bodies. To get an appreciation of the vast differences of size of the different bodies in our solar system, let’s shrink the sun down to the size of a soccer ball. In this scale, Jupiter would be the size of a walnut, and the Earth would only be the size of a peppercorn! The gaseous planets, unlike the terrestrial bodies, have a large number of moons. Saturn, the next largest planet, has 30 moons; and just recently, scientists have discovered that Jupiter has 39 moons! (However, many of these moons are much closer to the size of asteroids, not the size our nearest planetary neighbor.) To learn more about the different planets and moons in our solar system, visit the Jet Propulsion Lab’s at http://www.jpl.nasa.gov/solar_system/solar_system_index.html To learn more about the evolution of gas giants, refer to a previously answered question on a similar topic, http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=105 [How did the gaseous planets come to have so much atmosphere and so little solid surface?].
May 27, 2002