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On September 14, 2011, a team of astronomers revealed that the Milky Way’s spiral arms could have been generated after two collisions with SagDEG over the past billion years. As the galaxies collide, model simulations indicate that stars are sent streaming in long loops from both galaxies. These loops continue to swell with stars and are gradually tugged outward by the Milky Way’s rotation into ringed arms.
Больше разных интересностей и картинок на сайте http://www.solstation.com/x-objects/sag-deg.htm (pdf)
а тут: http://www.atlasoftheuniverse.com/250lys.html можно быстренько оценить масштабы видимой части вселенной.