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Luminous Red Novae

September 3, 2015

For stars that live alone, life is simple. They’re born, they evolve as they age, and they expire — quietly in some cases, more violently in others.

For a star with a close companion, though, life is a lot more complicated. Each star’s evolution can affect the other. And in the end, their interaction can sound almost metaphysical: the two stars can be “reborn” when they merge to form a single star.

Astronomers have discovered a couple of these mergers in recent months. One of them involved an event that was seen more than three centuries ago, while the other was observed just this year.

In 1670, a bright new star briefly flared to life in Vulpecula, the fox, which is high in the southeast at nightfall right now. For centuries, it was classified as a nova — an eruption caused by hot gas from one star piling on the surface of a companion. Recent observations, though, showed that debris around the system didn’t match what you’d expect from a nova.

And in January, astronomers saw a similar outburst happening in the Andromeda galaxy.

Each of these eruptions has been classified as a luminous red nova. Such an eruption is thought to be the result of a merger between two stars. As the stars come together, some of the gas in their outer layers is blasted into space, causing the system to flare to perhaps millions of times its normal brightness. The debris eventually fades away, leaving a rejuvenated single star where once there were two.

Script by Damond Benningfield, Copyright 2015

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