One of the brightest stars of summer is Vega, the lead star in the small but pretty constellation Lyra, the harp. And even though summer's about done, Vega's still in great view -- directly overhead at nightfall.
Lyra's home to many other wonders besides Vega, though. One of the most interesting is the constellation's second-brightest star, known as Beta Lyrae. It's a bit south of Vega.
Beta Lyrae is a binary -- two stars locked in a mutual orbit around each other. Both stars are larger, hotter, and brighter than the Sun -- one star is blue, and the other is white. But what's most remarkable is that the two stars are so close together that each star's gravity has distorted the other. That's because the blue star's gravity pulls hardest on the near side of the white star, and vice versa. So instead of being round, both stars look like eggs.
The two stars are so close together that they orbit each other once every 13 days. And during every orbit, one star passes in front of the other as seen from Earth, blocking its light. You can even see these eclipses with just your eyes. Just compare Beta Lyrae's brightness to that of Gamma Lyrae, the star that's next to it. Normally, they're the same brightness. But during an eclipse, Beta looks fainter, because you're seeing only one star instead of two.
Beta and Gamma Lyrae form the southern base of the harp. They're fairly easy to pick out -- not far from brilliant Vega.
Script by Ken Croswell, Copyright 2008
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