More Moon and Jupiter

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If you're heading for work or school early tomorrow, take a peek at the southeastern sky for a beautiful celestial pairing: the crescent Moon and the planet Jupiter. They're low in the sky at first light. Jupiter looks like a brilliant ivory-colored star a little above or to the upper right of the Moon.

Jupiter is the largest planet in the solar system, and by far the heftiest: it outweighs all the other planets and moons combined.

Yet despite its great bulk, Jupiter spins like a whirling ballerina. It makes one complete turn on its axis in less than 10 hours. At that rate, anyone floating in the clouds at Jupiter's equator would be moving at about 28,000 miles an hour -- fast enough to go all the way around Earth in less than an hour.

Since Jupiter is basically a ball of gas, though, different latitudes spin at different rates. So a day at the equator is about six minutes longer than a day at the poles.

The fast rotation stretches the clouds that top Jupiter's thick atmosphere into bands that encircle the entire planet. They're bounded by jet streams that blow in alternating directions at hundreds of miles an hour. Individual storms that spin through the cloud bands can have winds that are even stronger.

Jupiter's high-speed rotation has one more important effect: it pushes material outward at the equator, so Jupiter is several thousand miles fatter through the equator than through the poles.

Script by Damond Benningfield, Copyright 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.