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Moon and Pleiades

March 20, 2010

Two of the loveliest sights in the night sky snuggle close this evening: the crescent Moon and the Pleiades star cluster. They're high in the west at nightfall, and set after midnight.

The Pleiades is a cluster of hundreds of stars that's more than 400 light-years away. But only a few of its stars are bright enough to see with the unaided eye. Most people see six of them, while those blessed with dark skies and good eyesight may see eight or more. They form a tiny dipper.

The brightest of the Pleiades is Alcyone, a star that's several times heavier than the Sun, and hundreds of times brighter. It also spins faster than the Sun -- an indication that it's a good bit younger than the Sun is. As a star ages, its magnetic field acts as a brake, slowing its rotation.

Alcyone spins so fast that it throws some of its hot gas into space. The gas forms a disk around the star. It's so hot that it produces its own light. Analyzing this light reveals details about the star's composition.

Alcyone connects the bowl and handle of the dipper formed by the Pleiades. The Moon will pass just to the left of the dipper, a fraction of a degree from Alcyone and some of the other stars. This event is easily visible to the unaided eye, but binoculars will enhance the view. They'll reveal many more stars, plus some of the features on the dark portion of the Moon. Look for them as night begins to fall, and throughout the rest of the evening.

Script by Damond Benningfield, Copyright 2010

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