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Twin Crowns

August 8, 2010

The summer sky features two constellations that represent crowns. One of them is north of the celestial equator -- the projection of Earth's equator on the sky -- while the other is south of the equator.

The northern crown is Corona Borealis. According to one story, it was the crown that Bacchus, the god of wine, gave as a wedding present to Ariadne. When she died, Bacchus cast the crown into the sky.

Corona Borealis is a nice semicircle of seven stars between the bright stars Arcturus and Vega.

The constellation's leading light is Gemma. It's nearly as bright as the North Star, so it's fairly easy to pick out. It's a white star that's somewhat hotter than the Sun, and close to 60 times brighter. It's about 75 light-years from Earth.

Corona Borealis stands high in the west shortly after sunset. Although it's easy to see, it's not exactly a spectacle, so a star chart like the one in our Star Date magazine will help you find it.

The other crown -- the southern crown, Corona Australis -- is tougher to pick out. In fact, you need to be in the southern half of the United States to see it at all. Its stars are faint, and it's quite low in the sky. Look for it below teapot-shaped Sagittarius, which is in the south at nightfall.

Since the southern crown lacks bright stars, you may need to content yourself with the northern crown, a nice pattern of stars that's in view from the entire country.

Tomorrow: counting stellar nurseries.

Script by Ken Croswell, Copyright 2010

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