PLANET OF THE WEEK : jupiter

Jupiter takes about 12 years to orbit the sun and rotates in about 10 hours. This short Jupiter "day" is amazing since the planet is roughly 11 Earth diameters wide.
Unlike the rocky planets, Jupiter is a ball of dense hydrogen, helium, water, nitrogen and other gases over a tiny rocky core. Powerful winds dominate the atmosphere with criss-crossing jet streams, lightning and huge hurricane-like storms like the Great Red Spot. This storm has been raging for over 300 years and is about 2 Earth diameters wide. The Great Red Spot can be seen on Jupiter along with four moons: Io (smallest), Europa, Callisto and Ganymede in this NASA image.
The planet had 39 known moons at the time of this image and a slight ring of smoke-sized particles and dust. The planet contains 71% of the planetary matter in the solar system and so its huge gravity pulls every object toward it. In fact, most of its moons were captured rather than forming with Jupiter. Scientists watched in awe as comet Shoemaker-Levy 9 broke up and smashed into Jupiter making explosions the size of the Earth.
New Moons for JupiterScientists keep finding more moons orbiting Jupiter. In May of 2002 Scott S. Sheppard and David C. Jewitt of the University of Hawaii announced the discovery of 11 new moons around the planet. As of March, 2003, Jupiter had 52 confirmed satellites. These newest moons are all no more than 2 to 4 kilometers across (if their surfaces are very dark), they all have retrograde (backward) orbits, and take somewhere between 557 and 773 days to orbit. These latest moonlets were announced by the International Astronomical Union (IAU) on Circular number 8089. In April, 2003, 8 more moons were confirmed for a total of 60 moons with the possibility of more as the search continues.
The box below shows how the four main satellites or moons (Io, Europa, Ganymede and Callisto) of Jupiter would look in realtime (right now). If you have binoculars or a telescope you can see the moons as tiny points of light. If you look the next night you can see for youself that they move.