Appearances can be deceiving -- especially among the stars.
For an example, look at the stars that mark the points of the Summer Triangle, which is in view in the east and northeast at nightfall.
The brightest member of the trio is Vega, a brilliant star that's well up in the northeast. Yet Vega appears so bright in part because it's close by -- only about 25 light-years away.
The true luminary of the Summer Triangle is the star Deneb, which is to the lower left of Vega during the evening hours. It's probably a thousand times brighter than Vega, and at least a hundred thousand times brighter than the Sun. Astronomers are a bit uncertain of its true brightness because estimates of its distance vary by several hundred light-years.
Deneb is a type of star called a supergiant. Its diameter is probably a couple of hundred times that of the Sun. If it took the Sun's place in our solar system, Deneb would swallow all three of the innermost planets -- including Earth.
Deneb is also a couple of dozen times as massive as the Sun. That means it burns through the nuclear fuel in its core much faster than the Sun -- one reason that it shines so bright. And it'll live a much shorter life than the Sun; astronomers say it could blow itself to bits as a supernova in the next couple of million years.
Look for Deneb low in the northeast in early evening, and high overhead later on, trailing Vega across the summer sky.
Script by Damond Benningfield, Copyright 2004, 2008
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