Scientists believe the Milky Way is a cosmic thief, home-wrecker

Milky Way

Scientists at the Harvard-Smithsonian Centre for Astrophysics have determined that half of the 11 furthest known stars in the Milky Way were ripped from another galaxy known as the Sagittarius Dwarf.

“The star streams that have been mapped so far are like creeks compared to the giant river of stars we predict will be observed eventually,” said the lead author, Marion Dierickx, a graduate student at Harvard University in a press release.

According to the research, the Sagittarius Dwarf — just one of the dozens of mini-galaxies that surrounds our Milky Way — made its way around our galaxy at a point in the distant past. The research found that with each pass, the Milky Way tugged on the smaller galaxy, gradually dismantling it, and stealing some of its stars.

Scientists have observed that some of the stars within the Milky Way were ripped from a smaller galaxy

Dierickx and her PhD advisor Avi Loeb used computer models to record and simulate movements of the dwarf for the last eight million years. Varying its initial velocity and its angle of approach, they were able to determine which was the “best matched current observations”.

“The starting speed and approach angle have a big effect on the orbit, just like the speed and angle of a missile launch affects its trajectory,” said Loeb.

According to the research they collected, they found that the dwarf weighed one percent of the Milky Way’s mass. Dierickx’s calculations determined that over a course of time, the Sagittarius Dwarf lost a third of its stars and nine-tenths of its dark matter. The calculations also suggest that these stars now lie around one million light years from the centre of the Milky Way.

Their research also concluded that six of the 11 furthest known stars in our galaxy do not originate from the Saggitarius dwarf, but from a different dwarf galaxy. However, Dierickx concluded that “more interlopers from Sagittarius are out there just waiting to be found”.

Featured image: European Southern Observatory via Flickr



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