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Moon and Spica

April 24, 2013

Close binary stars aren’t exactly good neighbors. Each star in such a pair can steal gas from its companion, distort the other’s shape, and even change its entire evolution. And the two stars can fight a sort of duel, producing torrents of X-rays.

A couple of those things are happening right now in the star system known as Spica, which stands just a whisker above the Moon as night falls this evening.

Spica consists of two big, hot stars that are only a few million miles apart.

Both stars are much hotter than the Sun. Such stars blow thick “winds” of charged particles into space at millions of miles per hour. The winds from the two stars ram together, getting so hot that they produce a lot of X-rays. If any planets orbit Spica’s two stars, they’d have to be a long way out to be safe from this blast of energy.

The stars also pull on each other so strongly that they distort the other’s shape. Instead of nice, round balls like the Sun, the stars of Spica are tapered, like eggs.

As the stars age, their effects on each other will become more pronounced. The heavier of the two stars will soon expand to gigantic proportions, engulfing the smaller companion within its outer layers. No one is certain how that will affect the evolution of the two stars. Finally, the heavier star will explode - an event that’s likely to send whatever remains of its companion racing through the galaxy like a cannonball - given a final “kick” by its close neighbor.


Script by Damond Benningfield, Copyright 2013

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