The largest of the planets, Jupiter is a stormy place surrounded by more than five dozen moons.
Jupiter is the largest planet in the solar system, bigger than all the other planets combined. It is the fourth brightest object in the sky, after the Sun, Moon, and Venus. As the fifth planet in the solar system, it lies on the far side of the Asteroid Belt and is the gas giant planet closest to Earth. Jupiter is named after the king of the Roman gods.
Jupiter's year is equal to 12 Earth years, but its day is the shortest of any planet in the solar system at 10 hours. This means that it is possible to watch features on Jupiter appear and disappear on its surface during one observing session. The light-colored bands in Jupiter's clouds are called zones, and the dark-colored bands are called belts. The best-known feature of Jupiter is the Great Red Spot, a storm that has persisted since Jupiter was first seen up-close through a telescope by Galileo more than 300 years ago. The Great Red Spot is about three times the size of Earth. More recently, Jupiter has acquired a feature known as Red Spot Jr., a storm about half the size as the original and located in the same hemisphere.
Jupiter is a stormy place all over, not just in certain "spots." High winds and lightning are a regular feature in its cloud cover, along with aurorae that light up the polar regions just as they do on Earth.
Voyager and Galileo space probes have given scientists better views and more information about the planet, including revealing its thin ring.
In July 1994, scientists got an amazing treat when they were able to watch Comet Shoemaker-Levy 9 crash into Jupiter and leave a series of bruises in its cloud tops. Jupiter, being the second largest object in the solar system after the Sun, attracts comets and other space rocks in its vicinity by its large gravity.
Jupiter had 63 moons at last count. Smaller ones are found frequently through close examination of photographs. Just as Jupiter pulls in comets that crash into its surface, it also pulls in other space rocks such as those from the nearby Asteroid Belt, which enter into orbit around the planet, becoming new satellites.
The four largest moons are known as the Galilean moons, named after their discoverer. Ganymede is the largest moon in the entire solar system. It is even larger than Mercury. Ganymede's surface is icy and rocky.
Io, the closest moon to Jupiter, feels tidal stresses from the giant planet and has a cracked and seething crust, experiencing more volcanic activity than Earth. Io is bigger than our own Moon.
Callisto is the second biggest of Jupiter's moons. It has more craters than any other moon in the solar system. Callisto is farthest from Jupiter of the Galilean moons.
The smallest of the Gallilean moons, Europa is also one of the most mysterious. Europa appears to have a very smooth surface, with white lines stretching across it. This surface is a cracked, icy crust that may be sheltering a warm and wet ocean underneath.
For more on the solar system, follow the links below.
Sun Mercury Venus Earth Mars Saturn Uranus Neptune
