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The southern arm of M31

Tags: galaxy, spiral, elliptical, nebula, dust, cluster, globular, M31, Andromeda

M31 is the finest and nearest large spiral galaxy in the sky, about 2 million light years away. Despite its distance it can be seen as an elongated streak with the unaided eye in northern skies and in a large telescope under good conditions it is clearly resolved into stars and star-forming regions. This picture shows less than half the galaxy but the spiral structure, star clouds and dust lanes are evident. Also here is one of M31's close companions, the compact elliptical galaxy M32 (NGC 221), at upper left (NE). M31 and its companions belong to the Local Group of about 30 galaxies that includes the Milky Way and M31 as its most massive members as well as the Magellanic Clouds.

This picture is about half a degree across and is of the same region as the frontispiece in Hubble's famous book "The Realm of the Nebulae" (Harvard UP, 1936). In his illustration Hubble points out a Cepheid variable star, a globular cluster, a star cloud and open cluster as typical ingredients of a spiral galaxy. The star cloud is so conspicuous that it has its own New General Catalogue number, NGC 206 .

Photograph made from plates taken in October, 1991.
Top left is NE. Image width is about 38 arc min.

Credit: David Malin

© 1991-2002, David Malin/IAC/RGO (or David Malin/Instituto de Astrofisca des Canarias/Royal Greenwich Observatory)