- Galaxy merger
Galaxy mergers can occur when two (or more) galaxies collide. They are the most violent type of galaxy interaction. Although galaxy mergers do not involve stars or star systems actually colliding, due to the vast distances between stars in most circumstances, the gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies involved. The exact effects of such mergers depend on a wide variety of parameters such as collision angles, speeds, and relative size/composition, and are currently an extremely active area of research. There are some generally accepted results, however:
* When one of the galaxies is significantly larger than the other, the larger will often "eat" the smaller, absorbing most of its gas and stars with little other major effect on the larger galaxy. Our home galaxy, the
Milky Way , is thought to be currently absorbing smaller galaxies in this fashion, such as theCanis Major Dwarf Galaxy , and possibly theMagellanic Clouds . TheVirgo Stellar Stream is thought to be the remains of adwarf galaxy that has been mostly merged with the Milky Way.* If two
spiral galaxies that are approximately the same size collide at appropriate angles and speeds, they will likely merge in a fashion that drives away much of the dust and gas through a variety of feedback mechanisms that often include a stage in which there areactive galactic nuclei . This is thought to be the driving force behind manyquasars . The end result is anelliptical galaxy , and many astronomers believe that this is the primary mechanism that creates ellipticals.Note that the Milky Way and the
Andromeda Galaxy are predicted to collide and merge in about two billion years. The result would quite possibly be an elliptical galaxy as described above.One of the largest galaxy mergers ever observed consisted of four elliptical galaxies in the cluster CL0958+4702. It may form one of the largest galaxies in the Universe.cite news |url=http://news.bbc.co.uk/1/hi/sci/tech/6933566.stm |title=Galaxies clash in four-way merger |publisher=BBC News |date=
August 6 2007 |accessdate=2007-08-07]Examples
Some galaxies that are suspected to be in the process of merging:
*Antennae Galaxies
*Mice Galaxies
*Centaurus A
*NGC 7318 See also
*
Andromeda-Milky Way collision
*Bulge (astronomy)
*Galaxy formation and evolution
*Interacting galaxies References
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