Everyone talks about the beautiful rings of Saturn, or the glistening crescent of Venus. But, for my money, Jupiter's where it's at!

Brilliant Jupiter returns to the evening sky this week when it achieves "opposition" - that point where it lies directly opposite the sun in our sky and rises as the sun sets.

Opposition also means that it lies closest to Earth and appears larger and brighter than at any other time of the year. So Jupiter, which is always exciting to view through a small telescope, will be especially impressive over the next month or two. So why do I enjoy watching Jupiter more than any other planet? Because it actually does something.

Here's a world that's 11 times the diameter of Earth, yet it rotates on its axis once every ten hours or so. This means that its Earth-facing side changes completely in just five hours and, with patience, a stargazer with a small telescope can easily watch its pastel cloud bands and Great Red Spot spin around in just one full evening of viewing.

If that's not remarkable enough, consider this: Jupiter has in orbit around it 63 moons (at last count), and what I enjoy most is keeping up with the antics of its four largest. These are known as the Galilean satellites - Io, Europa, Ganymede and Callisto - because it was the Italian astronomer Galileo who discovered them and their movements four centuries ago.

These moons do-si-do around the Jovian disk from night to night - sometimes vanishing behind Jupiter or even casting their shadows onto the giant planet's cloud tops - and provide endless entertainment for the back-yard astronomer. Much of the fun of watching these moons is knowing which is which. You can identify them by visiting www.shallowsky.com/jupiter.html where you can type in the date and time and receive a graphic representation of their positions, along with that of the Great Red Spot. And to learn more about these incredible moons and their amazing parent planet, be sure to check out www.nineplanets.org/jupiter.html.
Now that Jupiter's back in the early evening sky, why not set up your telescope, or contact your local astronomy club to learn when they'll be hosting their next "star party" so you can get a close-up look at the exciting Giant Planet. Yes, sir! It's going to be a great summer of Jupiter-watching!

Dennis Mammana is an astronomy author and photographer, and can be reached via e-mail at mammana@skyscapes.com.
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