Messier 31 (M31), better known as the Andromeda Galaxy, is a large spiral galaxy located in the constellation
Andromeda. Lying at a distance of 2.54 million light years from Earth, the Andromeda Galaxy is the nearest major galaxy to our own. It is on a collision course with our home galaxy, the Milky Way. Messier 31 has an apparent magnitude of 3.44. Its designation in the New General Catalogue is NGC 224.
The Andromeda Galaxy was named after the area of the sky that it occupies, the constellation
Andromeda, which represents the princess Andromeda in Greek mythology. Andromeda was chained to a rock and left to a sea monster to appease Poseidon after her mother Cassiopeia had boasted that her daughter’s beauty surpassed that of the sea nymphs. The princess was saved by Perseus, the Greek hero represented by the neighbouring constellation.The Andromeda Galaxy is relatively easy to find in the sky as it is one of the brightest Messier objects. It lies in the vicinity of two prominent
asterisms in the northern sky: the
Great Square of Pegasus (formed by
Alpheratz,
Algenib,
Markab and
Scheat) and
Cassiopeia’s W. The only objects listed in Messier’s catalogue that are brighter than M31 are the
Pleiades (M45) and the
Ptolemy Cluster (M7).The Andromeda Galaxy is one of the most distant deep sky objects visible to the naked eye. The best time of year to observe it is during the months of October, November and December.In 10×50 binoculars, the galaxy appears as an oval shaped cloud with a bright nucleus. Binoculars and small telescopes reveal only the galaxy’s bright core, but larger instruments show its full size, which is six times larger than the apparent diameter of the full Moon. The Andromeda Galaxy’s brightest companions, the dwarf galaxies
Messier 32 and
Messier 110, can also be seen in binoculars.
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