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Former Neighbor

May 7, 2015

Neighbors come and go — in space as well as here on Earth. That’s because the stars all follow their own orbits around the center of the galaxy. So a star may sweep past our own solar system, becoming a close neighbor for a while before departing for other neighborhoods.

An example is a star system that was discovered in 2013. It’s only 20 light-years away, making it a close neighbor. But not so long ago, it was the closest neighbor — though it would have been too faint to see from Earth.

The system consists of a tiny, faint star known as a red dwarf, plus a failed star known as a brown dwarf. It’s been nicknamed Scholz’s Star for the astronomer who found it in observations by a space telescope.

Follow-up observations showed that the system is heading almost directly away from us — an indication that it once was much closer. 70,000 years ago, in fact, it passed just eight-tenths of a light-year from the Sun. By comparison, today’s nearest neighbor is five times farther.

The system probably passed through the edge of the Oort Cloud — a vast shell of comets around the Sun. If it had passed through the inner part of the cloud, it might have sent many of the big iceballs into the inner solar system — perhaps on a collision course with Earth. Such impacts could wipe out much of the life on our planet.

Fortunately, Scholz’s Star wasn’t an instrument of doom. But something else in the galaxy might be. More about that tomorrow.


Script by Damond Benningfield, Copyright 2015

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