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Evening Clusters

January 19, 2014

A bright, colorful triangle decorates the eastern sky as night falls this evening. It’s easy to spot because its bottom point is marked by the giant planet Jupiter, which looks like a brilliant cream-colored star. It far outshines any other planet or star in the sky at that hour, so it really stands out. The yellow-orange star Capella is well to the upper left of Jupiter, with orange Aldebaran roughly the same distance to the upper right of Jupiter.

Capella is the leading light of Auriga, the charioteer. And the constellation’s borders hold several star clusters — families of scores to hundreds of stars that are bound together by their mutual gravitational pull. They trickle off to the lower right of Capella.

The best known are Messier 36, 37, and 38. They’re easy targets for binoculars, with M37 the brightest of the three. It contains more than 500 stars, which may be up to 500 million years old. The other two clusters are younger and contain fewer stars.

Over the eons, all three clusters will lose some of their stars. Those at the edges of the cluster are more loosely bound than the ones near the center. The gravitational fingers of the rest of the galaxy’s stars eventually will pull these stars away. In fact, it’s possible that one or more of the clusters could completely disintegrate, with all of their stars going their separate ways — leaving their stellar homes for the wide-open spaces of the galaxy.


Script by Damond Benningfield, Copyright 2013

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