Fomalhaut
The southern third of the sky is a bit of a stellar wasteland on these early autumn evenings. Lots of stars speckle the sky, but almost all of them are faint and feeble. One exception is Fomalhaut, the "mouth" of the southern fish, Piscis Austrinus. The star just peeks above the southeastern horizon at nightfall, and scoots low across the sky later on.
Fomalhaut played in important role in ancient skylore, and it's playing an important role today in the effort to understand how planets are born.
In ancient Persia, Fomalhaut was one of four "guardians of heaven" -- bright stars that each ruled over a quadrant of the sky. Since there are no other bright stars anywhere close to Fomalhaut, it was an obvious choice for its patch of sky.
Fomalhaut itself isn't all that special, though. It's about twice as massive as the Sun, and about twice as big. Because of its heft, its surface is a good bit hotter than the Sun's, so the star shines pure white.
Estimates of its age vary, but it's probably around 200 million years old. Its mass dictates that it won't live more than about a billion years. By comparison, the Sun is already more than four times that old.
What makes Fomalhaut special is the environment around the star. It's encircled by a broad disk of gas and dust -- the ingredients for planets. And recent observations suggest that several planets may already circle inside the disk. More about that tomorrow.
Script by Damond Benningfield, Copyright 2006
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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