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On the Origin of Hyper-Velocity Stars Near Sagittarius A*

Research output: Contribution to Journal/MagazineJournal article

  • George Greenyer
  • Antonio Coulton
  • Josh Smith
  • Rhys Jaques
  • Nathan Wright
  • Keenan Wright
  • David Sobral
<mark>Journal publication date</mark>19/06/2020
<mark>Journal</mark>Notices of Lancaster Astrophysics (NLUAstro)
Number of pages13
Pages (from-to)29-41
Publication StatusPublished
<mark>Original language</mark>English


We present our investigation into the origins of high- and hyper-velocity stars around the Milky Way by exploring Gaia data. We begin by establishing a working set of criteria for a star to even be considered as a potential hyper-velocity star, which we defined chronologically as: if the uncertainty in parallax is acceptably low; if the star has above average total velocity for its home set; and finally if the star has a velocity that is mostly radial we investigate it further. We also discuss the complications encountered trying to identify candidate stars. Finally, we perform a time-reversing procedure to trace our final set of stars back to where they may have originated. We found a large number of candidate stars in our initial broad range search, but by enforcing stricter constraints we found a final sample of 1,158 potential hyper-velocity stars. This set displayed zero stars passing close enough to Sagittarius A* to have been thrown out or boosted to their current velocities. However, by selecting hyper-velocity stars with little proper motion in right ascension and declination, we discovered five stars which may have passed close enough to Sagittarius A* to have had their orbits significantly altered. A detailed analysis of the trajectories of those stars was performed, resulting in one star that may have originated from a binary system that had a close encounter with Sagittarius A*. We propose a potential binary partner in some of the known stars orbiting Sagittarius A* with similar periapsis.

Bibliographic note

Greenyer et al. (2020), NLUAstro, 2, 29