The Red Spot

Jupiter's most familiar feature is swirling mass of clouds that are higher and cooler than surrounding clouds. It has been likened to a great hurricane and is caused by tremendous winds that develop above the rapidly spinning planet. Winds blow counterclockwise around the Great Red Spot at about 250 miles per hour. Hurricanes on Earth rarely generate winds over 180 miles an hour.

The Red Spot is twice the size of Earth and has been raging for at least 300 years. It is one of several storms on Jupiter.

Hubble series shows changes in Jupiter's Red Spot
08/06/99: Shots taken over 7 years reveal diversity of the solar system's greatest storm.

Inside Jupiter

At Jupiter's center is a core of rock many times the mass of Earth. But the bulk of the planet is a thick gaseous murk that appears smeared through a telescope because the planet moves so rapidly beneath. Jupiter's rapid rotation causes it to bulge, making the diameter 7 percent greater at the equator than at the poles.

Around Jupiter

Jupiter has thin, barely perceptible rings and at least 16 satellites. The four largest-- Io, Europa, Ganymede and Callisto -- are called the Galilean moons. They orbit in the same plane and are all visible in a telescope. [Explore Jupiter's moons]

Historical notes

Jupiter was believed by Mesopotamians to be a wandering star placed in the heavens by a god to watch over the night sky. In 1610, Galileo Galilei used a 20x telescope to observe three stars around Jupiter; over several nights he observed the "stars," but each night they were in different positions, leading to his conclusion that they were bodies orbiting the giant planet.

In 1994, astronomers around the world watched as the fragments of comet Shoemaker-Levy 9 struck Jupiter, an event that had been forecast. This image shows a bright cloud more than 8,600 miles in diameter caused by the impact.

Final fact

You could stuff 1,300 Earths into Jupiter. ez

Explore Jupiter's moons >