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The Pleiades, the Hyades, and the Double Cluster

© Sonya Thomas-Haley

Winter is the best time to see the Pleiades. Sometimes called The Seven Sisters, this is actually a cluster of many more than seven stars. It contains about 200 stars and is about 400 light years away. It is conspicuous in the sky and easily found by following a line from Betelgeuse, the left shoulder of Orion, to red Aldebaran and extending the line out. This is a good test of your visual acuity. Most people see six stars. If you see more, congratulate yourself on your excellent vision (and you have my undying envy since I definitely don't possess such excellent vision). Because the stars are rather widely spread apart, they are best viewed either through binoculars or the finder scope of your telescope. Try and see if you can make out any of the faint, blue nebulosity around the stars. These are young, hot stars. When we think "hot" we usually think of the color red, but the hottest stars are actually blue.

The Hyades is right next to the star Aldebaran. It forms a large "V" shape. Aldebaran is not actually part of this cluster; it's only half the distance away from us as the Hyades. The cluster is about 130 light years away. It is part of a much larger group of much fainter stars called the "Taurus Moving Cluster." Over millions of years this cluster has been receding from us towards Orion. Millions of years hence, it will probably appear to be a small, faint, compact cluster. There is no nebulosity and no blue giants, so this cluster is rather elderly as clusters go.

The Double Cluster, NGC 869 and NGC 884 is a must see. It is located halfway between the "W" of Cassiopeia and the brightest star in the constellation Perseus. They are wonderful in binoculars. They are also a fine sight in a telescope although you might have trouble getting them both in the same field of view. Some of the stars are supergiants that shine some 50,000 times brighter than the sun. They are over 7,000 light years away. Imagine what they would be like if they were nearer to us. Such huge, bright stars live very short lives. They burn so much fuel so fast that they exist for only a small fraction of the lifetime of a star like our sun. Any cluster that has supergiants is therefore a young cluster.

The copyright of the article The Pleiades, the Hyades, and the Double Cluster in Amateur Astronomy is owned by Gregg Pasterick. Permission to republish The Pleiades, the Hyades, and the Double Cluster in print or online must be granted by the author in writing.