Epsilon Aurigae

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One of the highlights of autumn nights is Capella, the brightest star of Auriga, the charioteer. It climbs into view in the northeast by mid evening.

There are no other bright stars in that region of the sky, so Capella stands alone. But in a few decades, that may not be the case. Another star in Auriga may stage a violent outburst that could make it much brighter than Capella -- at least for a while.

Epsilon Aurigae is one of the oddest star systems in the galaxy.

Its main star is a supergiant -- it's as big as Earth's orbit around the Sun, and it's far brighter and more massive than the Sun.

But every 27 years, a dark companion passes in front of the star, cutting its brightness in half. The eclipse lasts a couple of years, which means that the companion must be gigantic. It could be a wide disk of gas and dust with two fairly small stars at its center. The next eclipse will begin in August.

Something else odd is happening in the system. The supergiant gets a little brighter and darker every couple of months. In recent years, the length of these "pulses" has been getting shorter. That could indicate that something is happening to the star itself. But one researcher thinks it could also mean that the disk of gas around the companion stars is dumping material onto the bright star. Whatever the reason, the researcher says the star may create a powerful explosion in a few decades -- making Epsilon Aurigae far outshine nearby Capella.

Script by Damond Benningfield, Copyright 2008

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