Messier 31: Difference between revisions

[[File:330px-WISE- Andromeda.jpg|thumb|The Andromeda Galaxy as seen by NASA's Wide-field Infrared Survey Explorer]]

According to a team of astronomers reporting in 2010, M31 was formed out of the collision of two smaller galaxies between 5 and 9 billion years ago. A paper published in 2012 has outlined M31's basic history since its birth. According to it, Andromeda was born roughly 10 billion years ago from the merger of many smaller protogalaxies, leading to a galaxy smaller than the one we see today.

The most important event in M31's past history was the merger mentioned above that took place 8 billion years ago. This violent collision formed most of its (metal-rich) galactic halo and extended disk and during that epoch Andromeda's star formation would have been very high, to the point of becoming a luminous infrared galaxy for roughly 100 million years. [[Messier 31]] and the [[Triangulum]] Galaxy ([[Messier 33]]) had a very close passage 2–4 billion years ago. This event produced high levels of star formation across the Andromeda Galaxy's disk – even some globular clusters – and disturbed M33's outer disk.