But where did it come from and why is it so fast to leave? Astronomers using the 3.9-meter Anglo-Australian telescope at the Australian National University's Spring Siding Observatory have found the star and made subsequent measurements to track its path.
The findings of the star, published on Tuesday in the Monthly Newsletter of the Royal Astronomical Society.
"We tracked this star's journey back to the center of our galaxy, which is quite exciting," says Gary Da Costa, author of the study and professor at ANU's Astronomy and Astrophysics Research School. This star travels at record speed – 10 times faster than most stars in the Milky Way, including our Sun.
Astronomers searched for the remains of small galaxies orbiting the Milky Way. The telescope they used can measure about 400 targets at a time. Instead, they found a star on the outskirts of the galaxy that had been struck there by a supermassive black hole in the center. The black hole is known as Sagittarius A * or Sgr A *. The black hole is 4.2 million times more massive than our sun.
If the black hole interacts with a binary star system that closes, the results can be tragic for the star system.
"If such a binary system approaches a black hole too close, a black hole can capture one star in close orbit and strike the other at very high speed," says Thomas Nordlander, co-author of the study and professor at ANU.
The star is 29,000 light-years from Earth and was struck by a black hole about five million years ago.
"Astronomically, the star will leave our galaxy relatively soon and will most likely travel through the void of intergalactic space for all eternity," said Costa. "It is great to be able to confirm a 30-year prediction that stars can be cast from a galaxy by a supermassive black hole in its center.
Astronomers plan to continue to track the star and obtain a more accurate measurement of its speed and position, thanks to the European Space Agency's Gaia satellite, according to Dougal Mackey, author of the study Annette and ARC Future Fellow in the Research School of Astronomy and Astrophysics at the Australian National University.
McKee said that there are a number of known "high-speed stars" like this, but special features separate the recently observed star.
"However, the two really special features of this star are that its velocity is much higher than other similar stars that were previously discovered (which all had speeds below 1000 km / s) and is the only one where we can let's be sure it came directly from the center of the Milky Way, "he said. "Together, these facts provide evidence of something called the Hills mechanism, which is a theoretical way for a supermassive black hole in the center of the Milky Way to cast stars at very high speeds."
Astronomers do not know how common these so-called The "expulsions" are, but they have a theory that one can happen every few hundred thousand years, he said.
Defining the orbits of these types of stars can also help astronomers understand and measure other parts of the galaxy. And understanding the composition and properties of a star born in the middle of the galaxy would shed light on stars that are otherwise difficult to observe.
"For this particular star, we hope to get better spectroscopic measurements that can allow us to determine its composition," Mackie said. "This is interesting because we think he was born right in the Galactic Center, which is a region that is very difficult to monitor in detail. So with this star, we can learn about the star formation conditions in this region and the composition of the gas that stars form. "