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StarDate: September 19, 2010

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The stars that form a constellation's familiar connect-the-dots pattern look like they're together. But that's usually just an illusion. In most cases, the stars lie at quite different distances from us. They appear together in our sky only because they happen to lie in the same direction from Earth.

An excellent example is one of the highlights of the autumn sky. Cassiopeia, the queen, glistens in the northeast at nightfall, and wheels high across the north later on.

The queen's five brightest stars form the shape of the letter W. And they certainly look as though they're together. But they're all at different distances. For example, the star at the top of the W -- Beta Cassiopeiae -- is 55 light-years away, while the next star down -- Alpha Cassiopeiae -- is 230 light-years away.

If you lived in another solar system, you'd view these five stars from a different vantage point, so they would make a different pattern.

Indeed, if you lived on a planet orbiting Alpha Centauri, your view of Cassiopeia would be profoundly different. Alpha Centauri is the nearest star system to the Sun -- just over four light-years away. From a planet around Alpha Centauri, Cassiopeia would have not five, but six bright stars. And the brightest of them would be one of the brightest in the night.

The star would look a bit yellow, because it would be none other than our own Sun -- adding a brilliant decoration to a beautiful queen.

 

Script by Ken Croswell, Copyright 2010

 

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