b'Carnegie Science|Spring/Summer 2020 19Runaway Star Ejected from Supermassive Black HoleIt was moving ten times faster than This artists concept shows the ultrafast star S5-HSV1, which was ejected frommost of the stars the Milky Way by the supermassive black hole at the galaxys center.in the galaxy.Image courtesy James Josephides, Swinburne A star traveling at ultrafastAstronomy ProductionsTing Li (left) is a Carnegie-speeds after being ejected by the supermassive black hole at the heart of our galaxy was spotted by an international team of astronomers including Carnegies Ting LiPrinceton Fellow and leads the Southern Stellar Stream and Alex Ji. Monthly Notices of the RoyalSpectroscopic Survey. Alex Ji Astronomical Society (right) is a Carnegie Hubblepublished their work. At the blistering speed of some 3.7Fellow, and he uses near-field cosmology in his research of the million miles per hour (6 millionfirst stars and galaxies.kilometers per hour), the star is moving so fast that it will leave the Milky Way,of such a fast star with the Galacticits going to leave our galaxy and die all blasting into intergalactic space.Center, said Koposov. We think the blackalone, out in the middle of nowhere. Quite Called S5-HVS1, the star was discoveredhole ejected the star with a speed ofa fall from grace.in the Grus, or Crane, constellation by leadthousands of kilometers per second aboutThe initial discovery was made on the author Sergey Koposov of Carnegie Mellonfive million years ago . . . when humanitysAnglo-Australian Telescope (AAT) and University, as part of the Southern Stellarancestors were just learning to walk onthen coupled with observations from the Stream Spectroscopic Survey (S5) led bytwo feet. European Space Agencys Gaia satellite, Carnegie-Princeton Fellow Li. It wasThirty years ago, astronomer Jackwhich allowed the astronomers to reveal moving ten times faster than most of theHills proposed that superfast stars could bethe full speed of the star.stars in the galaxy.ejected by black holes via a process bearingI am so excited this fast-moving star The velocity of the discovered star is sohis name. This is the first clearwas discovered by S5, added Kyler Kuehn high that it will inevitably leave the galaxydemonstration of the Hills Mechanism inof Lowell Observatory, a member of the S5 and never return, said coauthor Douglasaction, Li said. Seeing this star is reallyExecutive Committee. While the main Boubert of the University of Oxford. amazing, she added. As we know it mustscience goal of S5 is to probe the stellar High-velocity stars have been ahave formed in the Galactic Center, a placestreamsdisrupting dwarf galaxies and source of curiosity since their discoveryvery different from our local environment.globular clusterswe dedicated spare two decades ago. Because S5-HVS1 isIt is a visitor from a strange land.resources to searching for interesting moving so quickly and passed relativelyOriginally, S5-HSV1 lived with atargets in the Milky Way, and voil, we close to Earth29,000 light-years, close bycompanion in a binary system, but theyfound something amazing for free.astronomical standardsit presented anstrayed too close to Sagittarius A, the unprecedented opportunity to bettersupermassive black hole at the center of understand these phenomena. The uniquethe Milky Way. The companion star wasSUPPORT:The U.S. National Science Foundation, a Heising-Simons circumstances allowed the researchers tocaptured by the black hole, while S5-HVS1Foundation grant, a Magdalen College Fellowship by trace its journey right back to the center ofwas thrown out at extremely high speed. Examination, the Rudolf Peierls Centre for Theoretical Physics NASA Hubble Fellowship grants, the Australian the Milky Way, where there is black hole 4My favorite part of this discovery isResearch Council Discovery Project grants, and the Australian Research Council Centre of Excellence for All Sky million times the mass of the Sun.thinking about where this star came fromAstrophysics in 3 Dimensions supported this work.This is super exciting, as we haveand where its going, said Ji. It was bornThe research made use of data from the European Space Agencys Gaia Mission that was processed by the Gaia Data long suspected that black holes can ejectin one of the craziest places in theProcessing and Analysis Consortium (DPAC). National institutions, in particular the institutions participating in the stars with very high velocities. However,universe, near a supermassive black holeGaia Multilateral Agreement, provided funding for the DPAC.we never had an unambiguous associationwith lots of other nearby star friends; but'