Galaxies Collide in Colossal Collisions

Oldest stars in Milky Way Galaxy appear to be captured parts of other galaxies

The stellar halo of the Milky Way contains older stars astronomers believe were captured during a collision with another galaxy about 5 billion years in the Milky Way's past

Astronomers studying the oldest stars in the Milky Way Galaxy think that the most ancient stars in the Milky Way Galaxy could be parts of other galaxies that have been transferred or captured by the Milky Way Galaxy during gigantic collisions between galaxies. A new computer simulation conducted as part of a study supporting this idea is expected to appear in an upcoming issue of the Monthly Notices of the Royal Astronomical Society.

Andrew Cooper, of Durham University in the United Kingdom, and his fellow astronomers simulated the evolution of stars and dark matter, from 13 billions year in the past, to present time.

The Milky Way Galaxy has a disc containing young stars, including Sol, while the surrounding stellar halo is the home of stars as old as 10 billion years. Astronomers journeying to this part of space using their time machine to the stars search the stellar halo, much like archaeologists search ancient rock strata, to discern facts about the formation and life cycle of the Milky Way Galaxy. Astronomers in the United Kingdom report that the stellar halo contains stellar debris left over from a period of time during the life cycle of the Milky Way Galaxy that ended about 5 billion years ago, when smaller galaxies collided and ripped each other part.