04 November 2009

Dominating the Autumn Sky: Pegasus

In November, the nights grow longer and the sky changes rapidly. The Summer Triangle gradually fades into the west, and Orion and the winter constellations have not risen in the east to dominate the night sky. Instead, we see the less prominent (but no less beautiful) zodiac constellations of Capricornus, Aquarius and Pisces in the south, and directly overhead the large constellation Pegasus with the very distinctive asterism "The Great Square" in clear view. The sketch of the constellation Pegasus shown here is courtesy of the Battle Point Astronomical Association.

Pegasus is named after the Greek mythological character of the winged horse. Some constellations look a lot like their mythological namesake, but in this case I am always challenged to see the winged horse in the sky. But no matter, the shape of Pegasus is distinctive, and the Great Square makes it easy to find. This time of year Pegasus is high in the eastern sky after sunset and it moves almost directly overhead by 10 pm. I was out in my backyard a few minutes ago looking at it and to best see it I had to sit back on a chair. The Great Square is so striking because, yes, it is indeed nearly a perfect square, but more interesting is that there are virtually no other bright stars inside the square to disturb the shape. All around Pegasus, however, are a good number of bright stars, some of which form the head and feet of the winged horse, while the stars on the north side of the Great Square are actually part of Andromeda. In fact, I use Pegasus to help me find the constellation Andromeda and that points us to the Andromeda Galaxy (but that is a topic for another post).

For an excellent set of illustrations and tour of the Autumn sky, visit this webpage from the Smoky Mountain Astronomical Society.

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