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The nucleus of M31, (unsharp mask)

Tags: galaxy, spiral, dust, M31, Andromeda

At the heart of the nearby spiral galaxy M31 is a tiny, bright nucleus, seen to be slightly elongated on this colour picture. Hubble Space Telescope pictures show the nucleus to be a double structure, possibly the remains of the nucleus of another galaxy which has now been almost completely absorbed in M31. Around the binary nucleus swirls a huge cloud of mostly old, faint stars. These haze of stars is unresolved on the plates that were used to make this picture (same plates used for  INT 1) and have been removed by a photographic process known as 'unsharp masking'.

This not only reveals the inner nucleus but also shows traces of dust which seem to stream into the bright central part of the galaxy. Studies of the stars around the nucleus strongly suggest that at the heart of M31 there lurks a black hole, accelerating stars close to it to abnormally high velocities. Similar effects are seen in the Milky Way, but in our galaxy the nucleus is hidden at optical wavelengths, so observations are made in the infrared and at radio wavelengths. .

Photograph made from plates taken in October, 1991.
Top left is NE. Image width is about 15 arc min.

Credit: David Malin

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