A Star Ejected from the Milky Way's 'Heart of Darkness' Has Reached a Mind-Blowing Speed

As humankind's ancestors were learning to walk upright, a star was launched from the supermassive black hole at the center of our galaxy at a staggering 3.7 million mph (6 million km/h). 

Five million years after this dramatic ejection, a group of researchers, led by Sergey Koposov of Carnegie Mellon University's McWilliams Center for Cosmology, has spotted the star, known as S5-HVS1, in the Crane-shaped constellation Grus. The star was spotted traveling relatively close to Earth (29,000 light-years away) at unprecedented, searing speeds — about 10 times faster than most stars in our galaxy. 

"The velocity of the discovered star is so high that it will inevitably leave the galaxy and never return," Douglas Boubert, a researcher at the University of Oxford and a co-author on the study, said in a statement

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An artist's impression of the star S5-HVS1 being ejected by the Milky Way galaxy's supermassive black hole, Sagittarius A*. (Image credit: James Josephides (Swinburne Astronomy Productions))
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"This is super exciting, as we have long suspected that black holes can eject stars with very high velocities. However, we never had an unambiguous association of such a fast star with the galactic center," Koposov said in the statement. 

The star was discovered with observations from the Anglo-Australian Telescope (AAT), a 12.8-foot (3.9-meter) telescope, and the European Space Agency's Gaia satellite. The discovery was made as part of the Southern Stellar Stream Spectroscopic Survey (S5), a collaboration of astronomers from Chile, the U.S., the U.K. and Australia. 

Now that the star has been spotted, researchers could track the star back to Sagittarius A*, the black hole at the center of the Milky Way. It also serves as an incredible example of the Hills Mechanism, proposed by astronomer Jack Hills 30 years ago, in which stars are ejected from the centers of galaxies at high speeds after an interaction between a binary-star system and the black hole at the center of the galaxy.

The location and direction of the star S5-HVS1 in the night sky. The star is rocketing away from the center of our galaxy. (Image credit: Sergey Koposov)

"This is the first clear demonstration of the Hills Mechanism in action," Ting Li, a fellow  at the Carnegie Observatories and Princeton University who led the S5 collaboration, said in the statement. "Seeing this star is really amazing as we know it must have formed in the galactic center, a place very different to our local environment. It is a visitor from a strange land."

"While the main science goal of S5 is to probe the stellar streams — disrupting dwarf galaxies and globular clusters — we dedicated spare resources of the instrument to searching for interesting targets in the Milky Way, and voila, we found something amazing for 'free.' With our future observations, hopefully we will find even more!" Kyler Kuehn, deputy director of technology at the Lowell Observatory who is part of the S5 executive committee, added in the statement.

This discovery was published in a study on Nov. 4 in the journal the Monthly Notices of the Royal Astronomical Society. 

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Chelsea Gohd
Senior Writer

Chelsea “Foxanne” Gohd joined Space.com in 2018 and is now a Senior Writer, writing about everything from climate change to planetary science and human spaceflight in both articles and on-camera in videos. With a degree in Public Health and biological sciences, Chelsea has written and worked for institutions including the American Museum of Natural History, Scientific American, Discover Magazine Blog, Astronomy Magazine and Live Science. When not writing, editing or filming something space-y, Chelsea "Foxanne" Gohd is writing music and performing as Foxanne, even launching a song to space in 2021 with Inspiration4. You can follow her on Twitter @chelsea_gohd and @foxannemusic.

  • Roger M. Pearlman
    aligns as well w/ the YeC SPIRAL cosmological redshift hypothesis and model as well as SPIRAL's 'Black Hole illusion Resolution'
    where we find hyper-dense proto galactic formation preceded cosmic inflation expansion and the matter/energy that comprise each galaxy originated w/in the no longer dense black-hole at the approx. center of each galaxy.
    So yes it would have originated by our galactic center, like about all else in our galaxy.
  • Seattle7
    I'm not an astronomer, so maybe what I'm asking about is way off base, but is this ejection is similar to the discordant red shifts catalogued by Halton Arp? He noted that some quasars, which the standard model of the universe says are very distant objects, are associated with much nearer galaxies and that one interpretation (rejected by the astronomical community) was that they were ejected from the center of the associated galaxy.
    He also noted that these ejections occurred in pairs, with two objects being ejected in opposite directions along the minor axis of the galaxy. I wonder if there is another, similar object on the opposite side of the Milky Way.
    See Catalogue of Discordant Redshift Associations, Halton Arp, 2003.
    I know his theories are considered outlandish, but the data he presents has, to my very limited knowledge, not been invalidated.
  • rod
    Wow, someone reached back into the archives on space.com for this report :) This NASA ADS may help, Discovery of a nearby 1700 km/s star ejected from the Milky Way by Sgr A* The star is S5-HVS1, considered a main sequence star on the H-R star diagram and about 2.35 solar masses or larger than Sirius! As the NASA ADS Abstract reports, "When integrated backwards in time, the orbit of the star points unambiguously to the Galactic Centre, implying that S5-HVS1 was kicked away from Sgr A* with a velocity of ̃1800 km s-1 and travelled for 4.8 Myr to its current location." That is some astrometric back tracking here and kick to accelerate to some 1700 km/s as observed now. Note that the model interpretation for kicked out of Sgr A* (the black hole) and accelerated to such high velocity - is implied.