Gaia Sees Stars Out in Deep Space, Flying Between Galaxies

“Of the seven million Gaia stars with full 3D velocity measurements, we found twenty that could be travelling fast enough to eventually escape from the Milky Way."

"Stars can be accelerated to high velocities when they interact with a supermassive black hole. So the presence of these stars might be a sign of such black holes in nearby galaxies. But the stars may also have once been part of a binary system, flung towards the Milky Way when their companion star exploded as a supernova. Either way, studying them could tell us more about these kinds of processes in nearby galaxies.”

“We eventually expect full 3D velocity measurements for up to 150 million stars. This will help find hundreds or thousands of hypervelocity stars, understand their origin in much more detail, and use them to investigate the Galactic center environment as well as the history of our Galaxy."