An impression of the encounter between the Milky Way galaxy and the smaller Sausage galaxy about 8 billion to 10 billion years ago. Image credit: V. Belokurov (Cambridge, UK); based on image by ESO/Juan Carlos Muñoz
An international team of astronomers has discovered an ancient and dramatic head-on collision between the Milky Way and a smaller object, dubbed the “Sausage” galaxy. The cosmic crash was a defining event in the early history of the Milky Way and reshaped the structure of our galaxy, fashioning both its inner bulge and its outer halo, the astronomers report in a series of new papers.
The astronomers propose that around eight billion to 10 billion years ago, an unknown dwarf galaxy smashed into our own Milky Way. The dwarf did not survive the impact: It quickly fell apart, and the wreckage is now all around us.
“The collision ripped the dwarf to shreds, leaving its stars moving in very radial orbits” that are long and narrow like needles, says Vasily Belokurov of the University of Cambridge and the Centre for Computational Astrophysics at the Flatiron Institute in New York City. The stars’ paths take them “very close to the centre of our galaxy. This ...