Wednesday, July 25, 2018

Andromeda Galaxy Merged with a Massive Galaxy Long Ago

 According to new research published by scientists at the University of Michigan (UM), the Andromeda galaxy, the Milky Way's closest large galactic neighbour, merged and cannibalized a massive galaxy about two billion years ago. The decimated galaxy, known as M32p, would have been the third-largest member of the Local Group of galaxies, after the Milky Way and the Andromeda galaxies.
 Through new computer simulations, it was shown that most of the stars in Andromeda's outer faint halo were mostly contributed by the shredding of one large galaxy. The merger may also explain the thickening of the disk of the Andromeda galaxy as well as a burst of star formation that occurred about two million years ago.
 The theory also bodes well with the long-standing mystery of the formation of M32, the Andromeda galaxy's satellite galaxy. It is believed that the compact and dense M32 is likely the surviving centre of the cannibalized galaxy. “M32 is a weirdo,” said Eric Bell of UM. “While it looks like a compact example of an old, elliptical galaxy, it actually has lots of young stars. It’s one of the most compact galaxies in the universe. There isn’t another galaxy like it.” 
 “The Andromeda Galaxy, with a spectacular burst of star formation, would have looked so different 2 billion years ago,” Bell said. “When I was at graduate school, I was told that understanding how the Andromeda Galaxy and its satellite galaxy M32 formed would go a long way towards unravelling the mysteries of galaxy formation.”
 The method utilized by these scientists can be applied to other galaxies, allowing researchers insight into the largest galactic mergers in the universe. With these results, scientists can gain a better understanding behind the driving forces of galaxy growth and learn about what mergers do to galaxies.

Read the full press release at:
Or read the full study here:

Image: Andromeda galaxy with satellite galaxies M32 (center left) and M110 (lower right) via S. Ozime

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