A team of astronomers from the Chinese Academy of Sciences (NAOC) recently identified 591 new hyperspeed stars. Their work, led by Dr. Li Yinbi, is published in the issue of The Astrophysical Journal Supplement Series from December 17.
Most stars in the Milky Way behave predictably, orbiting the galactic center at speeds around 100 to 300 km/s. But some objects reach considerably higher speeds:these are the so-called "hyper-speed stars".
After being theorized in the 1980s, astronomers managed to prove their existence as early as 2005, with the discovery of a first star of its kind, and so far, 550 of these objects had been identified. In a new study, Chinese astronomers announce that they have isolated 591 more, doubling the known numbers. Among these newly discovered stars, 43 may even be able in the future to leave the gravitational constraints of the Milky Way, to finally soar into intergalactic space.
Researchers say they isolated these new stars in data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), China's largest optical telescope capable of observe approximately 4000 celestial targets in a single exposure. Commissioned in 2012, this telescope has established the largest spectra database in the world.
Astronomers also relied on the Gaia telescope, from the European Space Agency (ESA). Launched in 2013, this instrument has so far provided us with the astrometric parameters of more than 1.3 billion stellar sources. “These two massive databases have given us an unprecedented opportunity to be able to find more hyper-velocity stars” , explains Professor Luo Ali, co-author of this research.
According to the study, all of these stars evolve within the stellar halo of the Milky Way, most of which was formed from accretion and disruption tides of satellite galaxies. These space "sprinters" would therefore be from much smaller galaxies orbiting our own.
Recall that a few months ago, a team of astronomers announced that they had spotted another of these hyper-velocity stars moving at crazy speeds. At issue:a close encounter with our Galaxy's supermassive black hole.
Concretely, about five million years ago, a couple of stars indeed approached Sagittarius A*. One of them was probably eaten, but the other survived... Not without a good kick in the butt! This star called S5-HVS1, about 2.3 times more massive than the Sun, would indeed have benefited from a gravitational slingshot, propelling it into the Galaxy at more than 6 million km/h . The previous record was so far held by the star 708 US, flashed at 4.3 million km/h .
