| Messier number: |
M31 |
|
| Catalogue number: |
NGC224 | |
| Common name: |
The Andromeda Galaxy | |
| Constellation: |
Andromeda | |
| Magnitude: |
3.4 | |
| Type: |
Spiral Galaxy | |
| Right Ascension: |
00h:42.7' | |
| Declination: |
+41° 16.1' | |
| Size: |
178 x 63 arc mins | |
| Distance from Earth: |
2.9 million light years |
Once known as the Great Nebula in Andromeda, the famous naked eye spiral galaxy in Andromeda was discovered in ancient times and was described in 964 AD by the Persian astronomer Abd-al-Rahman Al-Sulfi, in his "Book of Fixed Stars", who called it "little cloud". It contains an estimated 3 billion suns, and is the nearest galaxy to our Milky Way. It was once thought that M31 was more massive than our Milky Way, but recent measurements made by the European southern Observatory's Very Large Telescope in Chile show Andromeda to be about 66% its size. M31 forms part of the local group of about 30 galaxies, which includes the Milky Way.
The Andromeda Galaxy is probably the most distant object that can be seen with the naked eye. Its a sobering thought to say we can see objects nearly 3 million light years away without optical aids! Andromeda and the Milky Way are moving towards each other due to mutual gravitational attraction, and eventually they will collide, but no need to worry, as this is way into the future, and our Sun will have become a red giant, and fried the Earth long before then.
M31 was catalogued by Charles Messier in 1764 who erroneously, attributed its discovery to Simon Marius, who had described it in 1612. Messier described it as "The beautiful nebula of the belt of Andromeda, shaped like a spindle", but its true structure was not understood until 1923 when Edwin Hubble found a Cepheid Variable in what was, until then, known as the Andromeda Nebula. There are several close companion galaxies, the most prominent are seen in the image above. They are M32 (NGC221)and M110 (NGC205.
Andromeda is unusual in that its centre contains two nuclei, thought to result from an earlier collision with another galaxy. A supernova was discovered in Andromeda in 1885, the first to be discovered beyond our own Milky Way galaxy.
Taken in December 2006
Canon EOS-5D (unmodified) through Skywatcher ED80Pro
telescope on LXD75 mount. Unguided.
Stacked in DSS, post processed in
Adobe Photoshop CS2.
Taken on 7th September 2007
24 x 300 secs Luminance unbinned, 24 x 75
secs each R,G,B binned 2 x 2. Average combined in MaximDL. Flats deducted, no
darks/bias.
Takahashi FS-102NSV telescope at prime focus F8
Starlight Express SXV-H16
Starlight Express Adaptive Optics Unit
Astronomik LRGB
filters
(With thanks to Peter Shah for post-processing the data)