A nearby galaxy throws hyperfast stars into the Milky Way

Have you ever seen a shooting star? No, not a blazing micrometeorite in the Earth's atmosphere – a real star, coming out of its orbit millions of kilometers to the hour in an infernal journey to explode this pop population of a galaxy and enter the intergalactic space.

Astronomers call them "hypervelocity stars" and represent the fastest stars in our galaxy. These rogue stars move so fast that they are not gravitationally bound to the Milky Way; Instead of turning around the center of the galaxy, as do our sun and billions of other people, many hypervelocular stars seem to be making their way down a path impossible to stop out of the Milky Way. Some may drift aimlessly across the intergalactic space. Others might one day immerse themselves in the hearts of distant and foreign galaxies, like cosmic expats.

And still others could already be extraterrestrials themselves. In a new study published on September 20 in the Avis journal of the Royal Astronomical Society, astronomers from the University of Leiden in the Netherlands have identified 13 new hypervelocity stars that can not be traced in any part of our galaxy. Instead of trying to get out of the Milky Way, these renegade stars seem to be introduced. [18 Biggest Unsolved Mysteries in Physics]

"Rather than flying out of the galactic center, most of the high velocity stars we've seen seem to be heading towards him," said co-author of the study, Tommaso Marchetti, a researcher at the University of California. Leiden Observatory, in a statement. "These could be stars from another galaxy, zooming in the Milky Way."

Marchetti and his colleagues identified these potential interstellar intruders by examining position and velocity data from more than 7 million Milky Way stars, provided earlier this year by the Gaia satellite of the Space Agency European. By searching specifically in the sky for the fastest stars in the galaxy, the researchers discovered 20 still unknown stars that could travel without ties to the gravity of the galaxy.

Seven of these stars seem to be "hyper-fugitives," she wrote, apparently from the galactic disk of the Milky Way and quickly heading toward intergalactic space. The remaining 13 stars seem to be moving on a trajectory that makes the intersection of the massive disk of the galaxy unlikely. More likely, the researchers wrote, these extraterrestrial stars came from a nearby galaxy such as the Great Magellanic Cloud (a satellite galaxy of the Milky Way, about a hundredth of our own) and sank a long time into our corner of the universe. since.

The two groups of stars represent some of the fastest stars ever detected in our galaxy, moving at several hundred million kilometers at the hour. (For comparison, solar satellites around the galactic center are at about 515,000 mph, or about 240 kilometers per second, according to NASA.)

How can a star be pushed so far and so fast out of its orbit? Astronomers believe that this has something to do with binary star systems (a pair of stars rotating one around the other or around a common focal point). ). If a star on a binary pair disappeared – for example, if it was sucked into a supermassive black hole or if it reached the end of its life and exploded in a supernova – astronomers believe that the resulting gravitational disturbance might be important enough for him kick partner fantastically out of the orbit.

"Anyway, studying them could tell us more about this type of process in nearby galaxies," said co-author of the study, Elena Rossi, theoretical physicist at the Leiden Observatory.

In 2017, astronomers had observed directly that about twenty hypervelocity stars, while their models estimated that there could be 10,000 or more that were circling around of our galaxy. This new study provides new evidence that a galaxy not far away, so far away, could give us stars – and with these stellar messengers we could perhaps get to know our neighbors better.

Originally posted on Live Science.