Red Nova

Two stars that recently merged into one threw up a thick veil of dust around themselves.

V1309 Scorpii first came to light in September of 2008, when a nova flared up in the beautiful constellation Scorpius, which is visible in the southern sky tonight. A nova is an exploding star, and most novae turn blue. But the nova in Scorpius was unusual, because it turned red instead.

By good luck, astronomers had been keeping an eye on this part of the sky. During the years leading up to the explosion, they’d made more than a thousand observations of the star. These observations revealed the star’s remarkable nature: it was really two stars that were stuck together, forming a contact binary. If Earth circled a contact binary, we’d see not a glowing sphere in the daytime sky, but a glowing peanut.

The pre-nova observations also indicated that the two stars were spiraling closer and closer together. They then merged into one, sparking the blast. At its peak brightness, it rivaled the most luminous stars in the entire galaxy.

Recent observations of V1309 Scorpii reveal that a thick blanket of dust formed shortly after the nova erupted. The single star born in the merger spun quickly, so it flung gas from its surface out into space. The gas cooled and turned red, accounting for the nova’s color. As the gas cooled, grains of dust also formed, blocking much of the light — almost as if the now-single star was seeking to block the view of outsiders like us.


Script by Ken Croswell, Copyright 2017

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