Messier 31: Difference between revisions

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-Andromeda Galaxy is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years; 2.4×1019 km) from Earth.Also known as [[Messier 31]], M31, or NGC 224, it is often referred to as the Great Andromeda Nebula in older texts. The Andromeda Galaxy is the nearest major galaxy to the Milky Way, but not thenearest galaxy overall. It gets its name from the area of the sky in which it appears, the constellation of Andromeda, which was named after the mythological princess Andromeda. The Andromeda Galaxy is the largest galaxy of theLocal Group, which also contains the Milky Way, the Triangulum Galaxy, and about 44 other smaller galaxies.
+[[File:420px-Andromeda Galaxy (with h-alpha).jpg|thumb|Messier 31 or Andromeda Galaxy]]
-The Andromeda Galaxy is the most massive galaxy in the Local Group as well.[7] Despite earlier findings that suggested that the Milky Way contains more dark matter and could be the most massive in the grouping,[12] the 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (1012) stars:[9] at least twice the number of stars in the Milky Way, which is estimated to be 200–400 billion.[13]
-The Andromeda Galaxy is estimated to be 1.5×1012 solar masses,[7] while the mass of the Milky Way is estimated to be 8.5×1011 solar masses. In comparison a 2009 study estimated that the Milky Way and M31 are about equal in mass,[14] while a 2006 study put the mass of the Milky Way at ~80% of the mass of the Andromeda Galaxy. The two galaxies are expected to collide in 3.75 billion years, eventually merging to form a giant elliptical galaxy [15] or perhaps a large disk galaxy.[16]
+Andromeda Galaxy is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years; 2.4×1019 km) from Earth.Also known as [[Messier 31]], M31, or NGC 224, it is often referred to as the Great Andromeda Nebula in older texts. The Andromeda Galaxy is the nearest major galaxy to the Milky Way, but not the nearest galaxy overall. It gets its name from the area of the sky in which it appears, the constellation of Andromeda, which was named after the mythological princess Andromeda. The Andromeda Galaxy is the largest galaxy of theLocal Group, which also contains the Milky Way, the Triangulum Galaxy, and about 44 other smaller galaxies.
+The Andromeda Galaxy is the most massive galaxy in the Local Group as well. Despite earlier findings that suggested that the Milky Way contains more dark matter and could be the most massive in the grouping, the 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (1012) stars:[9] at least twice the number of stars in the Milky Way, which is estimated to be 200–400 billion.[13]
+The Andromeda Galaxy is estimated to be 1.5×1012 solar masses, while the mass of the Milky Way is estimated to be 8.5×1011 solar masses. In comparison a 2009 study estimated that the Milky Way and M31 are about equal in mass, while a 2006 study put the mass of the Milky Way at ~80% of the mass of the Andromeda Galaxy. The two galaxies are expected to collide in 3.75 billion years, eventually merging to form a giant elliptical galaxy [15] or perhaps a large disk galaxy.
 At 3.4, the apparent magnitude of the Andromeda Galaxy is one of the brightest of any Messier objects,[17] making it visible to the naked eye on moonless nights even when viewed from areas with moderate light pollution. Although it appears more than six times as wide as the full Moon when photographed through a larger telescope, only the brighter central region is visible to the naked eye or when viewed using binoculars or a small telescope.
 Charles Messier catalogued Andromeda as object M31 in 1764 and incorrectly credited Marius as the discoverer, unaware of Al Sufi's earlier work. In 1785, the astronomer William Herschel noted a faint reddish hue in the core region of M31. He believed M31 to be the nearest of all the "great nebulae" and based on the color and magnitude of the nebula, he incorrectly guessed that it was no more than 2,000 times the distance of Sirius.