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Cited by 717Stellar, planetary, and galactic studiesAstrophysical Phenomena and ObservationsGalaxies: Formation, Evolution, Phenomena

The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy’s Central Black Hole: A Paradox of Youth

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Ghez, A. M., Duchêne, G., Matthews, K., Hornstein, S. D., Tanner, A., Larkin, J., Morris, M., Becklin, E. E. +6 more·2003·The Astrophysical Journal
DOI 10.1086/374804
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Abstract

We have obtained the first detection of spectral absorption lines in one of the high-velocity stars in the vicinity of the Galaxy's central supermassive black hole. Both Brγ (2.1661 μm) and He I (2.1126 μm) are seen in absorption in S0-2 with equivalent widths (2.8 ± 0.3 and 1.7 ± 0.4 Å) and an inferred stellar rotational velocity (220 ± 40 km s -1 ) that are consistent with that of an O8-B0 dwarf, which suggests that it is a massive (~15 M ☉ ) young (less than 10 Myr) main-sequence star. This presents a major challenge to star formation theories, given the strong tidal forces that prevail over all distances reached by S0-2 in its current orbit (130-1900 AU) and the difficulty in migrating this star inward during its lifetime from farther out where tidal forces should no longer preclude star formation. The radial velocity measurements ( = -510 ± 40 km s -1 ) and our reported proper motions for S0-2 strongly constrain its orbit, providing a direct measure of the black hole mass of 4.1(±0.6) × 10 6 3 M ☉ . The Keplerian orbit parameters have uncertainties that are reduced by a factor of 2-3 compared to previously reported values and include, for the first time, an independent solution for the dynamical center; this location, while consistent with the nominal infrared position of Sgr A*, is localized to a factor of 5 more precisely (±2 mas). Furthermore, the ambiguity in the inclination of the orbit is resolved with the addition of the radial velocity measurement, indicating that the star is behind the black hole at the time of closest approach and counterrevolving against the Galaxy. With further radial velocity measurements in the next few years, the orbit of S0-2 will provide the most robust estimate of the distance to the Galactic center.

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  • Our Galaxy contains a SMBH of mass Mbh≈4.14×10^6 M⊙ at its center, Sgr A*, at a distance D=8.127 kpc.

    “Our Galaxy is known to contain a supermassive black hole (SMBH) of mass M bh ≈ 4 . 14 × 10 6 M ⊙ at its center, Sgr A ∗ , at a distance of D = 8 . 127 kpc (Genzel et al. 1996; Schödel et al. 2002; Ghez et al. 2003; Genzel et al. 2010; GRAVITY Collaboration et al. 2019; EHT Collaboration et al. 2022a).”

    From The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way (2024) · cites this paper as Ghez et al. 2003

    The Introduction identifies a supermassive black hole at the Milky Way’s center associated with Sgr A*. Section 4.1 (Dynamics) estimates its mass as approximately (4.1 ± 0.6) × 10^6 solar masses, scaled to an assumed distance of 8 kpc. It does not give the claimed precise values of 4.14 × 10^6 solar masses and 8.127 kpc; it says the data did not yet yield a meaningful distance measurement. (LLM, conf=0.90)

    Experimental — accuracy not yet measured

  • The mass of the Milky Way black hole is approximately 4 × 10^6 solar masses.

    “very similar to the MW black hole, M bh ≈ 4 × 10 6 M ⊙ (Genzel et al. 1996; Schödel et al. 2002; Ghez et al. 2003; EHT Collaboration et al. 2022a).”

    From The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way (2024) · cites this paper as Ghez et al. 2003

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Research works printed but not linked: 2

  1. Ghez, A. M., Becklin, E. E., Duchene, G., Hornstein, S., Morris, M., Salim, S., & Tanner, A. 2003, Astron. Nachr., in press
  2. Wizinowich, P., Acton, S. D., Lai, O., Gathright, J., Lupton, W., & Stomski, P. 2000, Proc. SPIE, 4007, 2

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Authors
Ghez, A. M., Duchêne, G., Matthews, K., Hornstein, S. D., Tanner, A., Larkin, J., Morris, M., Becklin, E. E., Salim, S., Kremenek, T., Thompson, D., Soifer, B. T., Neugebauer, G., & McLean, I.
Affiliations
  • University of California, Los Angeles (US)
  • California Institute of Technology (US)
ORCID
Venue
The Astrophysical Journal
Publisher
American Astronomical Society
Published
2003-04-01
Volume
586
Issue
2
Pages
L127-L131
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
DOI
10.1086/374804
OpenAlex
W2003155983
Cited by
717
References
30
Citations by year
2026: 24 · 2025: 28 · 2024: 38 · 2023: 30 · 2022: 25 · 2021: 30 · 2020: 32 · 2019: 27 · 2018: 31 · 2017: 15 · 2016: 15 · 2015: 24 · 2014: 13 · 2013: 19 · 2012: 21
FWCI
40.10
Type
journal article
Language
en
Open access
Locations
  • The Astrophysical Journal (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • CaltechAUTHORS (California Institute of Technology) (submittedVersion)
  • CERN Document Server (European Organization for Nuclear Research) (submittedVersion)
  • arXiv (Cornell University)
Funders
  • National Science Foundation (9988397, 9876783)
  • National Aeronautics and Space Administration
  • W. M. Keck Foundation
  • California Institute of Technology
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
Keywords
Galactic Center, supermassive black holes, Sgr A*, black hole mass, stellar orbits, tidal disruption, young massive stars, stellar rotation, radial velocity, proper motions, Keplerian orbits, galactocentric distance

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