University of Michigan | 2019 Mar 12
A fast-moving star may have been ejected from the Milky Way’s stellar disk by a cluster of young stars, according to researchers from the University of Michigan who say the star did not originate from the middle of the galaxy, as previously believed by astronomers.Using one of the Magellan Telescopes in Chile as well as the data from the European
Space Agency (ESA) space mission Gaia, scientist recreated the trajectory of a massive
“hyper-runaway star.” The trajectory shows the star was ejected from the Milky Way
disk, not the Galactic center as previously believed. Image credit: Kohei Hattori
“This discovery dramatically changes our view on the origin of fast-moving stars,” said Monica Valluri... “The fact that the trajectory of this massive fast-moving star originates in the disk rather that at the Galactic center indicates that the very extreme environments needed to eject fast-moving stars can arise in places other than around supermassive black holes.”
Producing a fast-moving star requires lots of energy, usually found in extreme environments, Valluri said.
The Milky Way contains tens of billions of stars, most of which are distributed in a pizza-like structure called the stellar disk. In 2005, astronomers first discovered fast-moving stars that move more than twice as fast as most other stars—more than 1 million miles per hour, or 500 kilometers per second (310 miles/second), compared to the rest of the galaxy where stars average a bit more than 200 km/sec (124 miles/second).
Less than 30 of these extremely fast-moving stars (generally called “hypervelocity stars”) have been discovered so far. ...
Origin of a Massive Hyper-runaway Subgiant Star LAMOST-HVS1:
Implication from Gaia and Follow-up Spectroscopy ~ Kohei Hattori et al