Astronomers have identified group of more than 675 hypervelocity stars , which seem to have been pushed out of our on Milky Way galaxy.
The astronomers, Kelly Holley-Bockelmann and Lauren Palladino, say the group of hypervelocity stars they have identified have two characteristics that suggest they’re exiles from the Milky Way: they were found in intergalactic space between our galaxy and the neighbouring Andromeda, but their colour indicates that they originated close to the galactic centre. Their red colour isn’t, as you might guess, from their velocity: in this case, as Holley-Bockelmann explains, it comes from their high metallicity. Metallicity indicates a higher proportion of elements other than hydrogen and helium, which is most typical of stars around the core of a galaxy. Older stars, or stars that formed near the fringe of a galaxy, have lower metallicity. Even moving at hypervelocity speeds, these stars have been on the run for a long time, their 50,000 light-year trip from the centre to the edge of the Milky Way took about ten million years. To accelerate to galactic escape velocity, the stars’ encounter with the galactic supermassive black hole probably involved one of two scenarios, they were once members of binaries that got too close, with one star swallowed by the black hole, and the other accelerated outwards; or alternatively, while the supermassive was swallowing a smaller black hole, a passing star got a hypervelocity kick from the interaction. The next step will be that the researchers will determine as to whether some of the findings of brown dwarfs, which would indicate that they are much closer to Earth than it looks.