(M31 or NGC 224)
The Andromeda Galaxy, once known as The Great Nebula in Andromeda, is one of the largest members of what is called the Local Group. It is a spiral galaxy closest to our solar system, and is visible as a faint, misty spot in the Andromeda constellation. It is also classified as M31. This classification comes from it being the 31st object in a list first compiled by the 18th century French astronomer Charles Messier. This list was a list of things that were not comets, for which he was searching. Andromeda was even mistakenly believed to be a nebula prior to being observed by way of powerful telescopes.
The distance between M31 and the Milky Way galaxy is approximately 2.2 million light-years, and is the nearest spiral galaxy. This supports the fact that Andromeda is not an "open or globular" cluster in our Milky Way galaxy, but yet a tremendous independent celestial creation. Being classified as a spiral galaxy, Andromeda is characterized by a nuclear bulge, and by arched lanes of stars and glowing interstellar clouds, which appear as spiral arms. Andromeda is very similar in size and spiral configuration to our own galaxy. This galaxy is the only object, not part of the Milky Way that can be seen with the unassisted eye. Supported by a good observing environment, even the galaxy's bright central protuberance can be detected with the eye. This galaxy covers and area in the Northern Hemisphere's evening sky roughly five times as large as the full moon.
Although 2.2 million light-years away, M31 is close enough to us that images of its core, less than 1 pc across, can be resolved by the Hubble Space Telescope. These pictures enlightened the scientific community that this galaxy has two bright regions in its core or in other terms: a double nucleus. The dimmer region is believed to be its actual nucleus. The more luminous of the two has two ideology. The belief is that it could be a smaller galaxy that once intruded M31's core and possibly the remains of a violent dynamical encountering event in the earlier history of the Local Group. The second belief is that it is a cluster of stars. The brighter star cloud in the Andromeda galaxy has even been assigned its own NGC number: NGC 206. Stars within 50 light-years of the galaxy's nucleus are orbiting the nucleus at excessive speeds, which suggests that a massive object is located at the galaxy's center.
Also discovered by astronomers is the fact that the Andromeda and Milky Way galaxies are approaching each other with speeds of 300,000 miles per hour. A so called "collision scenario" has come into existence. Although the collision will take billions of years to occur, the final outcome will produce a single elliptical-shaped galaxy, intermingling both old and new stars. Also, many new stars will supposedly come into actuality when the two galaxies collide; mostly brilliant blue clusters, and hundreds of times more intense than the star clusters already existing. After the collision, Andromeda is thought to perchance take a U-turn lasting approximately 100 million years. "Any hint of the Milky Way and Andromeda as majestic spiral galaxies will be gone." (AstroFile).
Basic information on the Andromeda Galaxy:
Right Ascension 00 : 42.7 (h:m)
Declination +41 : 16 (deg:m)
Distance 2200 (kly)
Visual Brightness 3.4 (mag)
Apparent Dimension 178x63 (arc min)