Friday, February 3, 2012

Feb. Constellation of the Month -- Taurus

In January, we followed the band of the Milky Way from our December constellation to the constellation of Perseus. If we continue in that direction and along the band, we'll see the constellation of Auriga, which is shaped like a non-symmetrical pentagon. Auriga should be almost overhead an hour after sunset in February. Slightly south and west of Auriga, there is a prominent constellation which looks like the diagram to the left -- Taurus, the Bull.

The head of the bull is the triangle shape at the lower middle in the diagram shown here. The brightest star is Aldebaran. Aldebaran is a red giant star, nearing the end of its life; its diameter is 44 times as wide as the Sun. In about 5 billion years, the Sun will cool and expand and become a red giant itself.

The two horns of the Bull are marked by the two stars in the upper left of the diagram. Near the tip of the left horn is M1, the Crab Nebula. It is a cloud of expanding gases which are the aftermath of a star which exploded (a supernova) in the year 1054.

Aldebaran appears to be in the middle of a cluster of stars called "the Hyades", which fills up the triangle of Taurus's head. This is a group of about 200 stars that formed at the same time and which are moving together. Aldebaran is in our line-of-sight to this cluster, but it is much closer.

An even more interesting star cluster is the Pleiades, also known as the 7 Sisters. Somewhat north and west of Aldebaran, they form a uniquely memorable shape of a number of easily visible stars close together. The Subaru logo is taken from the shape of the Pleiades. Some people can see 5 stars with the naked eye, others 7, others more. A telescope will show hundreds of stars surrounded by a nebula -- a vast cloud of interstellar gases and dust. In many nebulae with star clusters, the stars were formed from the nebula. But in this case, they are just passing through each other -- at a speed of about 25,000 miles per hour.

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