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Great Andromeda Spiral Galaxy

Milky Way Galaxy, constellation Andromeda, Andromeda Galaxy, little cloud, Star Clusters

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>  Studying the Andromeda Galaxy

Great Andromeda Spiral Galaxy, also known as M31 and as the Andromeda Galaxy, large spiral galaxy in the constellation Andromeda, about 2.5 million light-years from Earth.

The Great Andromeda Spiral Galaxy is the largest nearby galactic neighbor to the Milky Way Galaxy, Earth’s home galaxy, and is part of the Local Group. Because it is so near, it appears very bright, with a total magnitude (a measure of its brightness as seen from Earth) of 3.4, and is easily visible to the naked eye on a clear, dark night. Its immense diameter of about 200,000 light-years makes it appear five times larger than the full Moon in our sky.

History of Observation

The first recorded observation of this galaxy was in ad 905 by Persian astronomer al-Sufi, who described it as the “little cloud” in his Book of Fixed Stars (964). The telescopic discovery of this object is often attributed to German astronomer Simon Marius who described the soft glow of the object in 1611 or 1612.

French astronomer Charles Messier entered the object as the 31st item in his Catalogue of Nebulae and Star Clusters (1771-1784) on August 3, 1764. The name M31 is referred to as the object’s Messier number, in which the M is followed by the number in Messier’s catalog.

Messier studied the galaxy with several instruments, including an excellent telescope, but could see no individual stars within, so he theorized that the object was a nebula, or cloud of gas and dust. It was not until 1923 that the American astronomer Edwin Hubble measured the distance to M31 and showed that it was not a nearby nebula but actually a distant galaxy like the Milky Way.

Article key phrases:

Milky Way Galaxy, constellation Andromeda, Andromeda Galaxy, little cloud, Star Clusters, M31, Local Group, dark night, brightness, Milky Way, naked eye, sky, measure, observation, light-years, galaxy, Moon, dust, Earth, distance, instruments, object, ad, August, item

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