Jupiter is the largest planet in the solar system. It is the fifth planet from the sun. It is eleven times wider than the earth and has three hundred times more mass. The planet spins faster than any other. Its average distance from the sun is 483,000,000 miles. Jupiter is named after the Roman king of the gods.
Four planets are called the outer planets because they are the most distant from the sun. Jupiter is the closest one to the earth. Beyond that are Saturn, Uranus, and Neptune. These planets are not solid but are made up of mostly gases and liquids. Jupiter consists of mostly hydrogen and helium. It has no solid surface. A space vehicle could never land on Jupiter. Astronomers think that the planet has a rocky or metallic core.
Stripes run parallel to the equator. The rapid rotation (only ten hours), strong winds and large movement of the gases on the planet create the stripes. The stripes are different layers of clouds. High clouds are white and lower clouds are reddish. The fast rotation also causes the planet to bulge at the equator and flatten at the poles. Jupiter has a layer of clouds thirty-one miles thick around the planet.
A day on the planet Jupiter is very short. The planet rotates on its axis every nine hours and fifty-five minutes. A day on Earth is twenty-four hours. However, Jupiter orbits the sun only every twelve years as compared to one year on Earth. Its year is twelve times as long as that of Earth.
In 1664, Robert Hooke discovered a red spot on the planet of Jupiter. It was a storm. However, 400 years later, it is still a storm. The explanation might be that since there is no land, and since a storm usually weakens over land, this storm keeps going.
A strong magnetic field occurs because energy flows through a layer of metallic liquid hydrogen in the inner part of the planet. This magnetic field can damage any spacecraft which might pass by. The radiation created by the magnetic field could kill a human very quickly.
The planet Jupiter has the strongest gravity of any planet. In the 1960's, the gravity was so strong that it pulled into its orbit a comet called Shoemaker-Levy 9. Later, the comet broke into pieces because of the strong pull of gravity and crashed onto the planet.
Because of its elliptical orbit, Jupiter's distance from the sun varies. Its farthest point is called the aphelion. This is 508,000,000 miles. The closest point is called the perihelion which is 460,000,000 miles. Earth also orbits the sun. Jupiter can be seen about every thirteen months when both planets are on the same side of the sun.
In 1979, the spacecraft Voyager 1 discovered that Jupiter has three rings. They are made up of dust particles from nearby moons and are very faint and almost transparent. The rings are called the halo, main and gossamer rings.
Because of Jupiter's strong gravity, it has attracted many moons. Sixty-seven are known at this time. Some were captured asteroids. The four largest moons are Io, Europa, Ganymede, and Callisto.
They are called the Galilean moons because they were discovered by the scientist, Galileo Galilei. He was looking at Jupiter through a telescope in 1610 and thought he saw stars. They moved with the planet, however, and he realized they were moons orbiting the planet.
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