More Moon and Jupiter

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The roster of moons that orbit the planets of the solar system is getting pretty long -- more than 160, and still counting. Most are chunks of bare rock with names that are bigger and more interesting than the moons themselves. Jupiter's retinue of more than 60 moons, for example, includes Eurydome, Kallichore, and Hermippe -- none of which is more than two or three miles in diameter.

But Jupiter also has some of the largest and most interesting moons in the solar system -- and some of them even have short names.

There's Io -- the most violent body in the solar system, with more than 400 active volcanoes. Some of them spew gas and ash hundreds of miles above Io's surface. Most of the material falls back to Io, but some of it goes into orbit around Jupiter.

Another of Jupiter's big moons is Europa, and it may be the most interesting of all. Its icy surface may float atop an ocean of liquid water. Volcanic vents at the bottom of this ocean could provide energy and nutrients for life. Scientists hope to someday search for life on Europa with a robotic submarine.

If you have binoculars, you can scan for Io and Europa -- along with two other satellites -- before dawn tomorrow. Jupiter is low in the southeast then. It looks like a brilliant star to the upper right of our own Moon. Through binoculars, Jupiter's big moons look like tiny stars flanking the planet, aligned roughly along the line between Jupiter and the Moon.

Script by Damond Benningfield, Copyright 2008

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