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Sagittarius galaxy impacts Milky Way's disk

Simulation showing impact of the Sagittarius galaxy on the disk of Milky Way

A computer simulation showing the impact of the Sagittarius galaxy on the disk of the Milky Way. This impact had a major influence on the development of the Milky Way's spiral arms; this spiral structure is clearly visible in the image. Also shown is the Sagittarius Stream, a long stream of stars and dark matter stripped from the Sagittarius galaxy by the gravitational pull of the Milky Way.

Research by astronomers at the University of California, Irvine, has found that the Sagittarius galaxy, a dwarf galaxy loaded with dark matter, has careened twice through our much larger home galaxy in the past 2 billion years--according to telescope data and detailed simulations--and is lined up to do so again. As the galaxies collide, the force of the impact sends stars streaming from both in long loops. These continue to swell with stars and are gradually tugged outward by the Milky Way's rotation into a familiar ringed arm.

To learn more about this research, see the UC-Irvine news story Milky Way's spiral arms are the product of an intergalactic collision course. [Research supported by National Science Foundation grant AST 06-07377.] (Date of Image: August 2011)

Credit: Erik Tollerud, Chris Purcell and James Bullock, University of California, Irvine
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