A dramatic head-on collision with a dwarf galaxy, dubbed the “Gaia Sausage” galaxy, about 10 billion years in the past reshaped the construction of our galaxy, the Milky Way, fashioning each its internal bulge and its outer halo, new analysis suggests.
The dwarf didn’t survive the affect. It shortly fell aside, and the wreckage is now throughout us, based on the findings.
“The collision ripped the dwarf to shreds, leaving its stars moving in very radial orbits” which might be lengthy and slim like needles, mentioned Vasily Belokurov of the University of Cambridge and the Center for Computational Astrophysics on the Flatiron Institute in New York City.
The stars’ paths take them “very close to the centre of our galaxy. This is a telltale sign that the dwarf galaxy came in on a really eccentric orbit and its fate was sealed.”
The outcomes detailed in a collection of recent papers within the journals the Monthly Notices of the Royal Astronomical Society, The Astrophysical Journal Letters and arXiv.org define the salient options of this extraordinary occasion.
Several of the papers have been led by Cambridge graduate scholar GyuChul Myeong. He and colleagues used knowledge from the European Space Agency’s Gaia satellite tv for pc.
This spacecraft has been mapping the stellar content material of our galaxy, recording the journeys of stars as they journey by the Milky Way.
Thanks to Gaia, astronomers now know the positions and trajectories of our celestial neighbours with unprecedented accuracy.
The paths of the celebrities from the galactic merger earned them the moniker the “Gaia Sausage,” defined Wyn Evans of Cambridge.
“We plotted the velocities of the stars, and the sausage shape just jumped out at us. As the smaller galaxy broke up, its stars were thrown onto very radial orbits. These Sausage stars are what’s left of the last major merger of the Milky Way,” Evans mentioned.
The new analysis additionally recognized no less than eight giant, spherical clumps of stars referred to as globular clusters that have been introduced into the Milky Way by the Sausage galaxy.
Small galaxies usually shouldn’t have globular clusters of their very own, so the Sausage galaxy will need to have been sufficiently big to host a set of clusters.
“While there have been many dwarf satellites falling onto the Milky Way over its life, this was the largest of them all,” mentioned Sergey Koposov of Carnegie Mellon University in Pittsburgh, Pennsylvania, US.