Cambridge Encyclopedia » Cambridge Encyclopedia Vol. 5

Andromeda (astronomy)

astronomer milky galaxy stars

A constellation in the N sky, one of 48 listed by Ptolemy (AD 140), named after the daughter of Cepheus and Cassiopeia. Its brightest stars are Alpheratz and Mirach. It contains the Andromeda galaxy, the largest of the nearby galaxies, c.725 kiloparsec away. It was mentioned by the Islamic astronomer as-Sufi in his book Book of Fixed Stars (AD 964), and rediscovered by the German astronomer Simon Marius in 1612. For centuries, astronomers regarded Andromeda as part of the Milky Way; only in the 1920s did the American astronomer Edwin Hubble establish without a doubt that it was a separate galaxy beyond the Milky Way. Spiral, like the Milky Way, about 45 kpc in diameter, it is the most remote object easily visible to the naked eye.

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