Our Heartless Milky Way Is Stealing Stars From Other Galaxies

Our thieving Milky Way stole a bunch of stars from unsuspecting galaxies — and it feels no remorse.

Artist’s conception of newly discovered galaxies / ICRAR

New research from the Harvard-Smithsonian Center for Astrophysics (CfA) suggests some of the 11 farthest stars in our galaxy — approximately 300,000 lightyears from Earth — were probably snatched from the Sagittarius dwarf galaxy. It’s the second-closest galaxy to our own, making it the perfect victim for this celestial crime.

Graduate student Marion Dierickx and her PhD advisor, Harvard theorist Avi Loeb, investigated the encounter by running computer simulations that tracked the Sagittarius dwarf galaxy’s movements, including its velocity and inclination, over eight billion years. The team found that as Sagittarius orbited the Milky Way, our galaxy’s gravitational pull tugged at the dwarf galaxy, swiping five or so stars in the process. Six other distant stars were probably pilfered from another neighbouring dwarf galaxy.

Harvard-Smithsonian Centre for Astrophysics (CfA)

Harvard-Smithsonian Center for Astrophysics (CfA)

In all, there’s been no justice for Sagittarius. Over time, it has lost a third of its stars to the Milky Way, along with 90 per cent of its dark matter. But Dierickx and Loeb hope the Sloan Digital Sky Survey at the Apache Point Observatory (APO) in Sunspot, New Mexico, and the soon-to-completed Large Synoptic Survey Telescope in Cerro Pachón, Chile will be able to find more stolen stars — and finally hold the Milky Way accountable for its actions.

“More interlopers from Sagittarius are out there just waiting to be found,” Dierickx said in a press release.

[Harvard-Smithsonian Center for Astrophysics (CfA)]