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Scorpius, the scorpion, skitters low across the southwest this evening. Its brightest stars form a pattern that really does look like a scorpion, with the bright orange star Antares right in the middle.
A few years back, astronomers made an astonishing discovery in Scorpius. For the first time ever, they saw two stars merge to form a single star.
In 2008, astronomers saw a strange explosion in Scorpius that was about 10,000 light-years from Earth. The explosion was a nova. Most novae are blue, but this one was red. Not only do red novae differ in color from normal novae, but they're also much brighter. Their cause had been a mystery.
By good luck, though, the nova in Scorpius happened to lie in a part of the sky that Polish astronomers were monitoring for planets and dark matter. As a result, the astronomers had observed the brightness of the object more than 1300 times before it became a nova.
The observations revealed that the star was a contact binary -- two stars that orbited each other so closely that they actually touched. Over time, the stars moved closer together, orbiting each other faster and faster. Then, in 2008, the stars merged, creating an explosion -- a red nova. It didn't destroy the stars, though -- it left behind a single star as a remnant.
Never before had astronomers seen such a remarkable metamorphosis. The discovery means that many red novae -- and perhaps all of them -- are born from the mergers of double stars.
Script by Ken Croswell, Copyright 2011