Running Away

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Running Away

Families of stars almost always break up. Usually, members drift away gradually. Sometimes, though, some of them run away from the family group in a big hurry.

An example is Mu Columbae. It’s in the constellation Columba, the dove, which is low in the south as night falls. The star is about 1300 light-years away. But it’s so brilliant that, under dark skies, it’s visible to the eye alone — but just barely.

Mu Columbae is one of the more impressive stars in our part of the galaxy. It’s about 16 times the mass of the Sun, and perhaps 45,000 times brighter. And it’s moving at about 260,000 miles per hour relative to the Sun. That’s far zippier than all but a handful of other stars.

Astronomers have discovered that Mu Columbae is moving in exactly the opposite direction from another runaway star, in Auriga the charioteer. Tracing their paths backward shows that they converge at a pair of massive stars in Orion.

The leading idea says the runaways began their high-speed journeys about 2.6 million years ago. Two pairs of massive stars passed quite close to each other. They staged a fast, violent gravitational dance. The heaviest members of the two pairs changed partners, forming a new binary. The less-massive members of the original systems were kicked out. So instead of run-aways, the stars are actually kick-aways — stars kicked out of the family by their weightier siblings.

Script by Damond Benningfield

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