Discovery of a star sensitive to the spin of Sagittarius A*

@article{dayem2026discovery,
  title = {{Discovery of a star sensitive to the spin of Sagittarius A*}},
  author = {K. Abd El Dayem and R. Abuter and N. Aimar and Pau Amaro‐Seoane and Anthony Berdeu and Jean-Philippe Berger and Guillaume G. Bourdarot and W. Brandner and Andreas M. Burkert and Diego Calderón and Carlos M Correia and Jorge Cuadra and R. Davies and Denis Defrère and L. Delit and A. Drescher and Frank Eisenhauer and Luis Esteras Otal and Maximilian Fabricius and H. Feuchtgruber and S. Flesch and N. M. Förster Schreiber and A. Foschi and Quentin Fournier and Paulo J V Garcia and R. García López and Aleksey Generozov and R. Genzel and S. Gillessen and Frédéric Gonté and X. Haubois and S. F. Hönig and M. Houllé and S. Joharle and A. Kaufer and J Kammerer and P. Kervella and Johann Kolb and Laura Kreidberg and Lucas Labadie and S. Lacour and Olivier Lai and Romain Laugier and J.-B. Le Bouquin and J. Leftley and R. Li and Bruno Lopez and Dieter Lutz and F. Mang and A. Mérand and Florentin A. Millour and M. Montargès and N. Morujão and H. Nowacki and Mathias Nowak and S. Oberti and J. Osorno and T. Ott and T. Paumard and C. Paladini},
  journal = {Nature},
  year = {2026},
  month = aug,
  doi = {10.1038/s41586-026-10894-w},
  url = {https://doi.org/10.1038/s41586-026-10894-w},
  note = {CC BY},
}

TY  - JOUR
TI  - Discovery of a star sensitive to the spin of Sagittarius A*
AU  - K. Abd El Dayem
AU  - R. Abuter
AU  - N. Aimar
AU  - Pau Amaro‐Seoane
AU  - Anthony Berdeu
AU  - Jean-Philippe Berger
AU  - Guillaume G. Bourdarot
AU  - W. Brandner
AU  - Andreas M. Burkert
AU  - Diego Calderón
AU  - Carlos M Correia
AU  - Jorge Cuadra
AU  - R. Davies
AU  - Denis Defrère
AU  - L. Delit
AU  - A. Drescher
AU  - Frank Eisenhauer
AU  - Luis Esteras Otal
AU  - Maximilian Fabricius
AU  - H. Feuchtgruber
AU  - S. Flesch
AU  - N. M. Förster Schreiber
AU  - A. Foschi
AU  - Quentin Fournier
AU  - Paulo J V Garcia
AU  - R. García López
AU  - Aleksey Generozov
AU  - R. Genzel
AU  - S. Gillessen
AU  - Frédéric Gonté
AU  - X. Haubois
AU  - S. F. Hönig
AU  - M. Houllé
AU  - S. Joharle
AU  - A. Kaufer
AU  - J Kammerer
AU  - P. Kervella
AU  - Johann Kolb
AU  - Laura Kreidberg
AU  - Lucas Labadie
AU  - S. Lacour
AU  - Olivier Lai
AU  - Romain Laugier
AU  - J.-B. Le Bouquin
AU  - J. Leftley
AU  - R. Li
AU  - Bruno Lopez
AU  - Dieter Lutz
AU  - F. Mang
AU  - A. Mérand
AU  - Florentin A. Millour
AU  - M. Montargès
AU  - N. Morujão
AU  - H. Nowacki
AU  - Mathias Nowak
AU  - S. Oberti
AU  - J. Osorno
AU  - T. Ott
AU  - T. Paumard
AU  - C. Paladini
PY  - 2026
DA  - 2026/08/19
JO  - Nature
DO  - 10.1038/s41586-026-10894-w
UR  - https://doi.org/10.1038/s41586-026-10894-w
AB  - Residing in the center of the Milky Way, Sgr A* is the closest massive black hole. Its vicinity has allowed measuring individual stellar orbits around it with periods as short as 12 years. The stars act as test particles and probe the gravitational potential around the 4.3 × 10^6 M_sun black hole. These observations have determined the central mass to sub-percent precision, and the mildly relativistic motions of stars have given access to seeing the dominant relativistic corrections, the gravitational redshift, the transverse Doppler effect and the prograde precession imposed by the Schwarzschild metric nature of the potential. These effects are of order (v/c)^2 (for velocity v and speed of light c). The Kerr metric occur- ring for a rotating black hole leads to corrections of order (v/c)^3. Here, we report the discovery of a faint main sequence star (mK = 19.3), S301, the orbit of which has a period of 8.7 years and small enough a pericenter distance, such that the star’s peak velocity reaches 25000 km/s or 8% of c. Within the measurement capabilities of current near-infrared interferometry and future spectroscopy on an extremely large telescope, S301’s motion is directly sensitive to the spin of Sgr A*. The high eccentricity of S301 suggests that it is the captured component of a binary that was torn apart via the Hills mechanism, sending the other component away as a hyper-velocity star.
SN  - 0028-0836
SN  - 1476-4687
ER  -