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Fast Neighbor

May 6, 2015

61 Virginis is a near twin to the Sun. It’s almost exactly the same size and mass, although it’s a bit cooler and fainter. And like the Sun, it has a family of planets. Astronomers have discovered three planets so far, all orbiting quite close to the star.

61 Virginis won’t stay where it is for long. It moves across the sky faster than all but a few other stars. It’ll shift position by one degree in just a few thousand years — about twice the width of the full Moon. That may not sound like much, but compared to most stars, 61 Virginis is like a runaway train.

One reason for the speed is the star’s distance — it’s just 28 light-years away, which makes it an especially close neighbor. Stars that are close appear to move faster than those that are farther away.

Another reason is that 61 Virginis really is moving at a high rate of speed relative to the solar system — roughly 140,000 miles per hour. That suggests that 61 Virginis may be an interloper from another part of the galaxy — perhaps hurled this way by an encounter with another star.

61 Virginis shows that the night sky is constantly changing — even if we can’t always see the difference. More about that tomorrow.

And 61 Virginis is just visible to the unaided eye. If you have clear, dark skies, in fact, you can find it this evening. Look for Spica, Virgo’s brightest star, in the southeast at nightfall. 61 Virginis is a few degrees to the lower right of Spica.


Script by Damond Benningfield, Copyright 2015

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