StarDate: September 7, 2009

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Even though summer ends in just a couple of weeks, its signature star pattern is still going strong.

In fact, the Summer Triangle stands high overhead as night falls throughout September. Its three points are Vega, which is almost directly overhead; Deneb, in the northeast; and Altair in the southeast.

Altair is the leading light of Aquila, the eagle. In fact, the name "Altair" comes from an Arabic phrase that means "the flying eagle." Altair and two moderately bright stars that flank it reminded long-ago skywatchers of a bird with outstretched wings. More about Altair tomorrow.

In Greek mythology, the eagle carried the thunderbolts of Zeus, the king of the gods. And the constellation launched a thunderbolt of its own more than 1600 years ago -- a stellar explosion that shined brighter than the planet Venus, which right now is the brilliant "morning star."

The explosion most likely was a nova. Such an explosion takes place when a small but hot stellar corpse known as a white dwarf steals gas from the surface of a bloated companion star. As the gas piles up on the surface of the white dwarf, it gets hotter and hotter. Eventually, it gets so hot that it triggers a nuclear explosion. The explosion blasts the layer of hot gas into space, and the white dwarf briefly shines thousands of times brighter than normal.

Early skywatchers described the brief appearance of a star where none had been seen before as a "new" star -- a nova.

Script by Damond Benningfield, Copyright 2009

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