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April 28, 2011

The Sun is an impressive star. It's brighter and more massive than probably 90 percent of the stars in the galaxy. It lights and heats our entire solar system all on its own.

But imagine a system where the Sun is the weak sister -- where a second star puts it to shame.

That's the case with Alphecca, the brightest star of Corona Borealis, the northern crown. It's in the east-northeast at nightfall, and climbs the eastern sky over the next few hours.

Although the eye alone sees a single point of light, Alphecca actually consists of two stars. One of them is quite similar to the Sun -- a bit smaller and fainter, but the same general type. Its companion, though, is much more impressive. It's about two-and-a-half times the Sun's diameter, and almost 70 times brighter than the Sun. And the two stars are quite close together -- much closer than the Sun and Mercury, the innermost planet in our solar system.

At that range, it's unlikely that planets orbit either of the individual stars. But it is possible that planets could orbit both stars.

From an orbit far away from these mismatched twins, the Sun-like star would look pale and puny, like the beam of a headlight next to a searchlight. So in this system, a star that's a lot like the Sun is little more than an afterthought.

Look for Alphecca at the center of the northern crown, a semicircle of stars that's in the eastern sky at nightfall, and crowns the sky in the wee hours of the morning.

Script by Damond Benningfield, Copyright 2011


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