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Delta Lyrae

July 10, 2011

Stars shine in different colors, and these colors look especially nice when they contrast with one another. And tonight, with the help of binoculars, you can see a double star that forms an especially colorful pairing. One star is red, while the other is blue.

It's known as Delta Lyrae. It's in the constellation Lyra, the harp. Lyra is easy to find, thanks to its brilliant star Vega, which is one of the five brightest stars in the night sky. The other stars of Lyra are much fainter, but if you have a star chart, you should be able to locate Delta Lyrae, not far from Vega.

The two stars of Delta Lyrae just happen to lie in the same direction from us. They're not related, so they're what astronomers call an "optical double" rather than a true double star. In fact, more than a hundred light-years of space likely separate the two stars.

Still, as viewed from Earth, the stars of Delta Lyrae form a pair. Look at them through binoculars and you'll see that the brighter star is red and the fainter one is blue, so they make a beautiful color contrast.

The colors are quite real. They indicate the surface temperatures of the stars. Red stars are cooler than the Sun, while blue stars are hotter than the Sun. So simply by looking at the two stars' colors, you can tell that one of them is hotter than the other -- a pretty amazing feat when you consider that both stars are many hundreds of light-years away.


Script by Ken Croswell, Copyright 2011


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