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Summer Triangle

June 13, 2014

The Moon is just a day past full tonight, so it fills the sky with light, overpowering the fainter stars. But some bright stars shine through. Among them are the points of the Summer Triangle — Vega, Deneb, and Altair. They’re in the east and northeast as twilight fades away, and climb high across the sky later on.

Vega is the triangle’s highest and brightest point. In fact, it’s one of the brightest stars in all the night sky, so it really stands out.

Vega looks so bright for a couple of reasons. First, it really is a bright star, outshining all but a tiny fraction of the other stars in the galaxy. And second, it’s quite close — only about 25 light-years away. At that range, its distance is known with great accuracy. Even so, there’s a small margin of error — about a light-month.

Altair is at the lower right of the triangle. The star is similar to Vega — a little smaller and cooler, but in the same general class. It’s only about a quarter is bright, though, so it looks fainter than Vega even though it’s closer.

Deneb is the triangle’s true luminary. It shines tens of thousands of times brighter than the Sun, so it’s easily visible even though it’s hundreds of light-years away. It’s one of the biggest, heaviest stars in our part of the galaxy. And while Vega and Altair face a quiet fate similar to the Sun’s, Deneb will expire as a supernova — a stellar blast that would outshine everything in the night sky except the Moon.

Script by Damond Benningfield, Copyright 2014

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