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The nucleus of the Andromeda galaxy, M31

Tags: galaxy, spiral, dust, Andromeda

The nearest comparable spiral galaxy to the Milky Way is M31 (NGC 224), the great galaxy in Andromeda. It is visible to the unaided eye and has been known as a curious hazy patch since ancient times. Only in the last 75 years has its nature as a distant city of stars like the Milky Way become apparent.

This picture covers almost half a degree of sky (about the size of the full moon), but wide angle telescopes show the galaxy to be over three degrees long at its widest. Here we see only the central part of M31, the huge mass of stars that are in orbit around its nucleus. Silhouetted against this starry background are tangled sheets and curtains of dust, very reminiscent of dust clouds we see in our own galaxy.

M31 is in the Local Group of galaxies of which the Milky Way is the other prominent member. These galaxies are gravitationally bound to each other and do not share in the general expansion of the universe. M31 and the Milky Way are approaching each other at a velocity of about 300 km per second, which is a very modest speed on the cosmic scale. Like all the images on these pages, this picture was made from three black and white glass negatives. Some care has been taken to ensure that the colours seen here are realistic.

Photograph made from plates taken in October, 1991.
Top left is NE. Image width is about 15.5 arc min.

Credit: David Malin

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