Kid's illustration of Jupiter and its moons.
You can sometimes see Jupiter's four largest moons with binoculars.

King of the Planets

Jupiter is the fifth planet from our sun. It is named for the king of ancient Roman gods. It is the biggest planet in our solar system. More than 1,300 Earths could fit inside it.

Color image of Jupiter.
Find Jupiter in the night sky.
If you look at it with binoculars,
you will see it as Galileo did
more than 400 years ago.

This is not a nice place to visit. It is a giant ball of gas. There is nowhere to land. Any spacecraft -- or person -- passing through the colorful clouds would get crushed and melted. Remember how your head feels squeezed when you dive into the deep end of a pool? That is pressure. On Jupiter, the pressure is so strong it squishes gas into liquid. Jupiter's atmosphere can crush a metal spaceship like a paper cup.

Jupiter's stripes and swirls are cold, windy clouds of ammonia and water. Jupiter's Great Red Spot is a giant storm as wide as three Earths. This storm has lasted hundreds of years. Jupiter's atmosphere is poisonous. It is mostly hydrogen and helium. Jupiter gets very hot and very cold. There is dangerous radiation, too. Talk about bad weather.

Scientists think Jupiter's core may be a thick, super hot soup. It might be up to 50,000 degrees Fahrenheit (27,760 degrees Celsius) down there.

Jupiter has its own "mini solar system" of 50 moons. Scientists are most interested in the Galilean satellites -- the four largest moons discovered by Galileo Galilei in 1610. Europa, may have an ocean under its frozen surface. Callisto's crater-pocked landscape may be the oldest in the solar system. Ganymede is the solar system's largest moon. It is bigger than Pluto and Mercury. And little Io has more volcanoes than anyplace else in the solar system.

Jupiter also has three rings, but they are very hard to see and not nearly as pretty as Saturn's.