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November 6, 2013

A faint but famous princess crowns the sky on November evenings. Andromeda is high in the east as night falls, and directly overhead by around 10 o’clock.

The constellation is marked by a slightly curved line of three equally bright stars. Alpheratz is at the top right of the line, and does double duty as one of the corners of the Great Square of Pegasus. Mirach is at the middle of the line, and is about the same brightness as Alpheratz.

Almach — also known as Gamma Andromeda — is at the bottom left of the line. It’s slightly fainter than the other two, but perhaps the most interesting of the bunch. That’s because it’s a family of at least four stars. A small telescope shows it as two stars — one that shines golden yellow, the other blue-white.

The yellow-orange one is the brightest member of the quartet, and is known as Gamma 1 Andromeda. It’s bigger, heavier, and brighter than the Sun. Part of the reason is that the star is at the end of its life, so it’s puffed up to giant proportions. Before long, it’ll cast off its outer layers, leaving behind only its tiny, hot, dead core — a white dwarf.

The other three stars form Gamma 2 Andromeda. They’re pretty close together, so even through a small telescope their light blurs together to form a single point. All three of the stars are hotter than the Sun, so they shine white or blue-white — forming a nice contrast to their golden companion.

We’ll have more about Andromeda tomorrow.


Script by Damond Benningfield, Copyright 2013

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