A supermassive black hole flung a star out of the Milky Way
Black holes are mysterious, strange, and a little scary. As it turns out, they may very well be bullies, too. Astronomers recently noticed a star careening through the Milky Way at nearly 4 million mph which is a surprising 10 times faster than the sun. Scientists predict that, at that speed, it could exit our galaxy for good, never to return. Using the Anglo-Australian Telescope at the Australian National University's Siding Spring Observatory, researchers were able to pinpoint additional details and where it came from, as well as why it seemed to be in a massive rush to leave our neck of the space woods.
The responsible party? A supermassive black hole at the center of our solar system.
"We traced this star's journey back to the center of our galaxy, which is pretty exciting," Gary Da Costa, study author and professor at the ANU Research School of Astronomy and Astrophysics, explained. Originally, the scientists had planned on sifting through their findings for the remains of smaller galaxies orbiting the Milky Way, but the star they happened upon was a much more interesting catch. The stray star, pushed out by the supermassive black hole at the center of our universe, Sagittarius A*, served as a stark reminder of what could potentially happen to a star system or even a planet if somehow it got too close.
"If such a binary system approaches a black hole too closely, the black hole can capture one of the stars into a close orbit and kick out the other at very high speed," said Thomas Nordlander, professor at ANU as well as co-author on the study. Case in point: the star now on the outskirts of the galaxy is now about 29,000 lightyears away from Earth. It was sent hurtling through space around 5 million years ago, and will probably continue traveling indefinitely. As in it won't stop. It literally can't.
"In astronomical terms, the star will be leaving our galaxy fairly soon and it will likely travel through the emptiness of intergalactic space for an eternity," Da Costa explained. "It's great to be able to confirm a 30-year-old prediction that stars can be flung out of a galaxy by the supermassive black hole at its center."
As it turns out, this isn't the only "hyper velocity" star that scientists have seen in the past. This one, however, was traveling at a much higher speed than other in the past. It's also the only one that anyone can be sure of that came directly from the center of the Milky Way.
"The two really special features of this star, though, are that its speed is much higher than other similar stars that were previously discovered (which all had velocity below 1000 km/s) and it's the only one where we can be almost certain that it has come directly from the center of the Milky Way," study co-author Dougal Mackey explained."Together those facts provide evidence for something called the 'Hills mechanism' which is a theorised way for the supermassive black hole in the center of the Milky Way to eject stars with very high velocity."
The same researchers who discovered this now outcast star are looking to learn more about it in a bid to figure out what it's made of. They believe it was born right at the Galactic Center, which is an area that's already difficult for them to observe in great detail. It looks like this unfortunate star may very well help them unlock the key to understanding others in the same location. Unfortunately, it looks like this particular star is destined to remain lonely as it careens through space. Black holes are jerks.