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Facts About The Andromeda Galaxy for Kids


  • The Andromeda Galaxy is the nearest spiral galaxy to our Milky Way galaxy, but not the closest 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 the Local Group, which also contains the Milky Way, the Triangulum Galaxy, and about 30 other smaller galaxies.
  • Although the largest, the Andromeda Galaxy may not be the most massive, as recent findings suggest 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 stars: at least twice the number of stars in the Milky Way galaxy, which is estimated to be 200–400 billion.
  • The Andromeda Galaxy is estimated to be 7.1×10 solar masses.
  • At an apparent magnitude of 3.4, the Andromeda Galaxy is notable for being one of the brightest Messier objects, making it visible to the naked eye on moonless nights even when viewed from areas with moderate light pollution.
  • Charles Messier catalogued it as object M31 in 1764 and incorrectly credited Marius as the discoverer, unaware of Al Sufi’s earlier work.
  • He believed it to be the nearest of all the “great nebulae” and based on the colour and magnitude of the nebula, he incorrectly guessed that it was no more than 2,000 times the distance of Sirius.
  • The Andromeda nebula was very similar to the spectra of individual stars, and from this it was deduced that M31 had a stellar nature.
  • The result was the largest velocity recorded at that time, at 300 kilometres per second (190 mi/s), moving in the direction of the Sun.
  • As a result he was able to come up with a distance estimate of 500,000 light-years (3.2×10 AU).
  • M31 plays an important role in galactic studies, since it is the nearest spiral galaxy (although not the nearest galaxy).
  • Based on his observations of this galaxy, he was able to discern two distinct populations of starsbased on their metallicity, naming the young, high velocity stars in the disk Type I and the older, red stars in the bulge Type II.
  • Radio emission from the Andromeda Galaxy was first detected by Hanbury Brown and Cyril Hazard at Jodrell Bank Observatory using the 218-ft Transit Telescope, and was announced in 1950 (Earlier observations were made by radio astronomy pioneer Grote Reber in 1940, but were inconclusive, and were later shown to be an order of magnitude too high).
  • In the 1990s, measurements of both standard red giants as well as red clump stars from the Hipparcos satellite measurements were used to calibrate the Cepheid distances.
  • This violent collision formed most of its (metal-rich) galactic halo and extended disk and during that epoch Andromeda’s star formation would be very high, to the point of becoming a Luminous infrared galaxy during roughly 100 millon years.
  • There have been interactions with satellite galaxies like M32, M110, or others that have already disappeared absorbed by M31 that have formed structures like Andromeda’s Giant Stellar Stream and a merger roughly 100 million years ago that is behind a counter-rotating disk of gas found in the center of M31 as well as the presence there of a relatively young (100 million years) stellar population.
  • In 2005, a group of astronomers consisting of Ignasi Ribas (CSIC, Institute for Space Studies of Catalonia (IEEC)) and his colleagues announced the discovery of an eclipsing binary star in the Andromeda Galaxy.
  • Scott Tremaine has proposed that the observed double nucleus could be explained if P1 is the projection of a disk of stars in an eccentric orbit around the central black hole.
  • There are approximately 460 globular clusters associated with the Andromeda Galaxy.