55 Cancri

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With eight "official" planets, our solar system is the most planet-rich star system that we know of. But a system in the constellation Cancer is catching up. Astronomers have discovered five planets there, and they're looking for more.

The system is known as 55 Cancri. It's about 40 light-years away, and its star is similar to the Sun.

Astronomers discovered the first planet orbiting 55 Cancri in 1996. They announced the discovery of the fifth planet just last year. All the planets are giants, and they're all pretty close to the star itself, so the system is quite different from our own.

Even so, the most recently discovered planet is intriguing, because it's at the right distance from the star for liquid water -- a distance known as the habitable zone. Since water's a key ingredient for life, any planet that could have water is considered a possible home for life.

Unfortunately, the planet is about 45 times as massive as Earth. Such giants aren't good candidates for life. But if the planet has any moons, they could offer a friendlier environment -- perhaps a solid surface, a thick atmosphere, and pools of water.

55 Cancri soars high overhead tonight. It's not visible to the unaided eye, but you can see it through binoculars, near the constellation's northern edge. It's about halfway between two bright planets -- orange Mars, which is high overhead at nightfall, and golden Saturn, which is about halfway up the eastern sky.

Script by Damond Benningfield, Copyright 2008

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