The nucleus of M31, unsharp mask
AAO image reference INT 2.    « Previous || Next »
Nucleus of M31
Top left is NE. Image width is about 15 arc min
© 1991-2002, Malin/IAC/RGO. Photograph from Isaac Newton Telescope plates by David Malin.


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.

Entry from NGC 2000.0 (R.W. Sinnott, Ed.) © Sky Publishing Corporation, 1988:
NGC  224  Gx 00 42.7  +41 16 s  And 178. 3.5  !!! eeB, eL, vmE (Andromeda); = M31
More data about this galaxy is accessible from the hotlinked NGC name and is reproduced
with permission from the NASA/IPAC Extragalactic Database (NED).

Related images
INT 1.  The nucleus of M31, direct image
INT 3.  The southern arm of M31 (NGC 224) and M32 (NGC 221)
Caltech M31The Andromeda galaxy, M31 and its companions.

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