Hills mechanism

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

The Hills mechanism[1] is a phenomenon that occurs when a binary star system is disrupted by a supermassive black hole.

Tidal forces from the black hole cause one of the stars to be captured by it, and fall into an orbit around it. The other star is jettisoned away from the black hole at very high speeds. The phenomenon, proposed by astronomer Jack Hills in 1988 and confirmed in 2019, when an example of such a jettisoned star was observed.[2] This ejected star, namely S5-HVS1, an A-type main-sequence star, notable as the fastest star detected as of November 2019, has been determined to be traveling at nearly four million miles an hour (more specifically, 1,755 km/s (3,930,000 mph)) away from the galactic core of the Milky Way.[3][4][5][6][7][8][9][10][11]


  1. ^ Hills, J. G (25 February 1988). "Hyper-velocity and tidal stars from binaries disrupted by a massive Galactic black hole". Nature. 331 (6158): 687–689. Bibcode:1988Natur.331..687H. doi:10.1038/331687a0.
  2. ^ Gohd, Chelsea (November 13, 2019). "A Star Ejected from the Milky Way's 'Heart of Darkness' Has Reached a Mind-Blowing Speed". Space.com. Space.com. Retrieved November 14, 2019.
  3. ^ Overbye, Dennis (14 November 2019). "A Black Hole Threw a Star Out of the Milky Way Galaxy - So long, S5-HVS1, we hardly knew you". The New York Times. Retrieved 18 November 2019.
  4. ^ Koposov, Sergey E.; et al. (11 November 2019). "Discovery of a nearby 1700 km/s star ejected from the Milky Way by Sgr A*". Monthly Notices of the Royal Astronomical Society. arXiv:1907.11725. doi:10.1093/mnras/stz3081.
  5. ^ Starr, Michelle (31 July 2019). "Bizarre Star Found Hurtling Out of Our Galaxy Centre Is Fastest of Its Kind Ever Seen". ScienceAlert.com. Retrieved 18 November 2019.
  6. ^ Irving, Michael (13 November 2019). "Fastest star ever found is being flicked out of the Milky Way". NewAtlas.com. Retrieved 18 November 2019.
  7. ^ Imster, Imster (18 November 2019). "Black hole hurls star out of Milky Way - Astronomers have spotted a star – S5-HVs1 – speeding out of the Milky Way at around 4 million miles (more than 6 million km) per hour. They believe it's being ejected from our galaxy after venturing too near the giant black hole at the Milky Way's heart about 5 million years ago". Earth & Sky. Retrieved 18 November 2019.
  8. ^ Gohd, Chelsea (12 November 2019). "A Star Ejected from the Milky Way's 'Heart of Darkness' Has Reached a Mind-Blowing Speed - It is a visitor from a strange land". Space.com. Retrieved 18 November 2019.
  9. ^ Staff (15 November 2019). "A Runaway Star Ejected from the Galactic Heart of Darkness". Carnegie-Mellon University. Retrieved 18 November 2019.
  10. ^ Lincoln, Don (13 November 2019). "Supermassive Black Hole Ejects Star From Milky Way Galaxy". Forbes. Retrieved 18 November 2019.
  11. ^ Plait, Phil (13 November 2019). "Our Local Supermassive Black Hole Shot A Star Right Out Of THe Galaxy". Bad Astronomy. Retrieved 19 November 2019.