There's no mistaking Jupiter in the sky these late spring evenings, rising above the southeastern horizon just as the sun is setting later and later. Jupiter is by far the brightest starlike object in that part of the sky and, even with a smaller telescope, you can see some of the cloud bands that circle the gargantuan 88,000-mile wide planet.

Want to see something Galileo Galilei saw, something that got him in a lot of trouble? While you're enjoying Jupiter through your scope, about 400 million miles away right now, look for four little stars on either side of Jupiter. These are four of Jupiter's over 60 moons, gravitationally enslaved to the mighty massive planet.

From night to night they constantly change their alignment with Jupiter as they orbit the great planet in periods of two to 17 days. Some nights you don't see all four of the moons, because one or more of them may be either behind or in front of Jupiter, lost in the backdrop of the planet's glow. On the diagram, the alignment of Jupiter's moons is shown for the coming week. A great Web site to keep up with Jupiter's moons is from the University of Maryland: /www.astro.umd.edu/~lgm/astr120_fall97/jupiter.html

These four moons are referred to as the Galilean moons because Galileo Galilei watched them as often as he could with his small telescope in the early 1600s. He didn't quite know the nature of either Jupiter or the moons but definitely concluded that the moons were orbiting Jupiter.

The century prior, the famous Polish astronomer Nicolas Copernicus proposed that the sun, and not the Earth, was the center of the solar system. Back then the government and Catholic Church treated that as sheer heresy. To suggest that Earth was not the center of the solar system got you in big time trouble, so much so that Copernicus didn't publish his theory until the day he died. Galileo was privately a big fan of the Copernican theory. When he observed Jupiter's moons circling the planet, he reasoned that if Jupiter could be the center of its own little universe why couldn't the sun be an astronomical hub?

He published his observations and theories and was convicted by the church and sentenced to house arrest for the rest of his life. It wasn't until 1992 that Pope John Paul II finally pardoned Galileo — better late than never!

Thanks to the fleet of robotic spacecraft that have visited or passed by Jupiter in the last 30 years, we know a lot more about the Galilean moons.

The two outer moons, Callisto and Ganymede, are the largest of Jupiter's moons, with diameters of around 3,000 and 3,300 miles respectively, both way bigger than our own moon.

Callisto is the most heavily cratered object we know of in the solar system, just over a million miles from Jupiter.

Ganymede, about 700,000 miles from the big mother planet, is the largest moon in the solar system, even larger than the planet Mercury. It has mountains, valleys, and even lava flows, but not much of an atmosphere.

The two most interesting moons by far are the inner Galilean moons, Europa and Io. The surface of Europa is a giant sheet of cracked ice about three miles thick.

Astronomers don't know for sure, but beneath the ice there may be warmer oceans of water that could harbor some kind of life. As far away as Jupiter and its moons are from the sun, you may wonder how it could be warm enough for liquid water on Europa. The heat inside Europa is the result of the extremely strong tidal forces of Jupiter, less than 400,000 miles away. Who knows, maybe they'll be ice fishing on Europa's surface some day.

Those same strong tidal forces literally raise hell on Io, Jupiter's closest moon, only 260,000 miles from the giant. It's only about 1,100 miles in diameter, but it's the most volcanically active body in the solar system. Because of the constant volcanic eruptions, Io's surface is a chaotic mix of reds, oranges, yellows, and grays. In fact, Io is referred to as the "pizza planet" by many astronomers. Many of these eruptions, some spewing almost 200 miles above the surface, have been caught easily by the cameras of space probes. Recently the New Horizon probe on the way to Pluto imaged some fantastic eruptions on Io.

Enjoy Jupiter's dancing moons and keep in the back of your astronomical minds some of the bizarre happenings on Galileo's little friends.

Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and author of the book, "Pennsylvania Starwatch," available at bookstores and at his Web site www.lynchandthestars.com.