# Gaia BH2

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Binary system in Centaurus

Gaia BH2 DECaPS image of Gaia BH2 (star at the center) Observation data Epoch J2000 Equinox J2000 Constellation Centaurus[1] Right ascension 13h 50m 16.748s[2] Declination −59° 14′ 20.33″[2] Apparent magnitude (V) 12.711[3] Characteristics Red giant Evolutionary stage Red giant branch[2] Black hole Evolutionary stage Stellar black hole[4] Astrometry Radial velocity (Rv) −5.04±2.08[2] km/s Proper motion (μ) RA: −10.48±0.1 mas/yr[4] Dec.: −4.61±0.06 mas/yr[4] Parallax (π) 0.859±0.018 mas[4] Distance 3,800 ± 80 ly (1,160 ± 20 pc) Orbit[4] Period (P) 1,276.7±0.6 d Semi-major axis (a) 4.96±0.08 AU Eccentricity (e) 0.5176±0.0009 Inclination (i) 34.87±0.34° Longitude of the node (Ω) 266.9±0.5° Periastron epoch (T) 2457438.3±1.4 Argument of periastron (ω) (secondary) 130.9±0.4° Semi-amplitude (K1) (primary) 25.23±0.04 km/s Details Red giant Mass 1.17±0.08[5] M☉ Radius 8.55+0.20 −0.15[5] R☉ Luminosity (bolometric) 24.6±1.6[4] L☉ Surface gravity (log g) 2.71±0.24[4] cgs Temperature 4,604±87[4] K Metallicity [Fe/H] −0.22±0.02[4] dex Rotation 398±5[5] days (preliminary estimate) Rotational velocity (v sin i) <1.5[4] km/s Age 5.1+1.2 −1.8[5] Gyr Black hole Mass 8.94±0.34[4] M☉ Other designations Gaia BH2, UCAC4 154-126202, 2MASS J13501675-5914203, Gaia DR3 5870569352746779008 Database references SIMBAD data

**Gaia BH2** (Gaia DR3 5870569352746779008) is a [binary system](/source/Binary_system) consisting of a [red giant](/source/Red_giant) and a [stellar-mass black hole](/source/Stellar-mass_black_hole). Gaia BH2 is located about 3,800 [light years](/source/Light_year) away (1.16 [kpc](/source/Parsec#Parsecs_and_kiloparsecs) away) in the constellation of [Centaurus](/source/Centaurus), making it as of 2024[\[update\]](https://en.wikipedia.org/w/index.php?title=Gaia_BH2&action=edit) the [third-closest known](/source/List_of_nearest_known_black_holes) black hole system to Earth. Gaia BH2 is the second black hole discovered from [Gaia DR3](/source/Gaia_DR3) astrometric data.[4]

The black hole and red giant orbit the system [barycentre](/source/Barycentre) every 1,277 days, or around 3.5 years, with a moderate eccentricity of 0.518. The black hole's mass is around 8.94 [M☉](/source/Solar_mass), which means its [Schwarzschild radius](/source/Schwarzschild_radius) should be about 26.4 km (16.4 mi).[4] The red giant has a mass of 1.17 [M☉](/source/Solar_mass) and a radius of 8.6 [*R*☉](/source/Solar_radius).[5] Its temperature is estimated at 4,604 [K](/source/Kelvin) (4,331 [°C](/source/Celsius); 7,828 [°F](/source/Fahrenheit)).[4] The star is enriched in [alpha elements](/source/Alpha_elements), and thus is believed to have undergone mass transfer with another star.[5]

## Discovery

Gaia BH2 was originally discovered as a black hole binary candidate in 2022, found via [astrometric](/source/Astrometry) observations with [Gaia](/source/Gaia_(spacecraft)), along with [Gaia BH1](/source/Gaia_BH1). At that time it was not clear if Gaia BH2 did definitely harbour a black hole, but it was the only plausible candidate in the Gaia data other than Gaia BH1.[6][7] Later radial velocity observations confirmed this black hole system and refined its orbital parameters.[4]

## See also

- [List of nearest known black holes](/source/List_of_nearest_known_black_holes)

- [Gaia BH1](/source/Gaia_BH1)

- [Gaia BH3](/source/Gaia_BH3)

## References

1. **[^](#cite_ref-constellation_1-0)** [Roman, Nancy G.](/source/Nancy_Roman) (1987). ["Identification of a constellation from a position"](https://doi.org/10.1086%2F132034). *[Publications of the Astronomical Society of the Pacific](/source/Publications_of_the_Astronomical_Society_of_the_Pacific)*. **99** (617): 695. [Bibcode](/source/Bibcode_(identifier)):[1987PASP...99..695R](https://ui.adsabs.harvard.edu/abs/1987PASP...99..695R). [doi](/source/Doi_(identifier)):[10.1086/132034](https://doi.org/10.1086%2F132034). [Constellation record for this object](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?source=VI%2F42%2Fout&%2F%2Ftables=VI%2F42%2Fout&-c=UCAC4+154-126202&-c.eq=J2000&-c.r=++2&-c.u=arcmin&-c.geom=r&-source=&-source=VI%2F42%2Fout&-out=RA1875&-out=DE1875&-out=Cst) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-GaiaDR3_2-0) [***b***](#cite_ref-GaiaDR3_2-1) [***c***](#cite_ref-GaiaDR3_2-2) [***d***](#cite_ref-GaiaDR3_2-3) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D5870569352746779008%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. **[^](#cite_ref-ucac4_3-0)** Zacharias, N.; Finch, C. T.; Girard, T. M.; Henden, A.; Bartlett, J. L.; Monet, D. G.; Zacharias, M. I. (2012-07-01). "VizieR Online Data Catalog: UCAC4 Catalogue (Zacharias+, 2012)". *VizieR Online Data Catalog*: I/322A. [Bibcode](/source/Bibcode_(identifier)):[2012yCat.1322....0Z](https://ui.adsabs.harvard.edu/abs/2012yCat.1322....0Z).

1. ^ [***a***](#cite_ref-elbadry_4-0) [***b***](#cite_ref-elbadry_4-1) [***c***](#cite_ref-elbadry_4-2) [***d***](#cite_ref-elbadry_4-3) [***e***](#cite_ref-elbadry_4-4) [***f***](#cite_ref-elbadry_4-5) [***g***](#cite_ref-elbadry_4-6) [***h***](#cite_ref-elbadry_4-7) [***i***](#cite_ref-elbadry_4-8) [***j***](#cite_ref-elbadry_4-9) [***k***](#cite_ref-elbadry_4-10) [***l***](#cite_ref-elbadry_4-11) [***m***](#cite_ref-elbadry_4-12) [***n***](#cite_ref-elbadry_4-13) El-Badry, Kareem; Rix, Hans-Walter; Cendes, Yvette; Rodriguez, Antonio C.; Conroy, Charlie; Quataert, Eliot; Hawkins, Keith; Zari, Eleonora; Hobson, Melissa; Breivik, Katelyn; Rau, Arne; Berger, Edo; Shahaf, Sahar; Seeburger, Rhys; Burdge, Kevin B. (2023-02-01). ["A red giant orbiting a black hole"](https://doi.org/10.1093%2Fmnras%2Fstad799). *[Monthly Notices of the Royal Astronomical Society](/source/Monthly_Notices_of_the_Royal_Astronomical_Society)*. **521** (3): 4323–4348. [arXiv](/source/ArXiv_(identifier)):[2302.07880](https://arxiv.org/abs/2302.07880). [Bibcode](/source/Bibcode_(identifier)):[2023MNRAS.521.4323E](https://ui.adsabs.harvard.edu/abs/2023MNRAS.521.4323E). [doi](/source/Doi_(identifier)):[10.1093/mnras/stad799](https://doi.org/10.1093%2Fmnras%2Fstad799).

1. ^ [***a***](#cite_ref-Daniel2025_5-0) [***b***](#cite_ref-Daniel2025_5-1) [***c***](#cite_ref-Daniel2025_5-2) [***d***](#cite_ref-Daniel2025_5-3) [***e***](#cite_ref-Daniel2025_5-4) [***f***](#cite_ref-Daniel2025_5-5) Hey, Daniel; Li, Yaguang; Ong, Joel (2025-03-12). "Asteroseismology of the red giant companions to Gaia BH2 and BH3". [arXiv](/source/ArXiv_(identifier)):[2503.09690](https://arxiv.org/abs/2503.09690) [[astro-ph.SR](https://arxiv.org/archive/astro-ph.SR)].

1. **[^](#cite_ref-eb2023_6-0)** El-Badry, Kareem; Rix, Hans-Walter; Quataert, Eliot; Howard, Andrew W.; Isaacson, Howard; Fuller, Jim; Hawkins, Keith; Breivik, Katelyn; Wong, Kaze W. K.; Rodriguez, Antonio C.; Conroy, Charlie; Shahaf, Sahar; Mazeh, Tsevi; Arenou, Frédéric; Burdge, Kevin B. (2023-01-01). ["A Sun-like star orbiting a black hole"](https://doi.org/10.1093%2Fmnras%2Fstac3140). *Monthly Notices of the Royal Astronomical Society*. **518** (1): 1057–1085. [arXiv](/source/ArXiv_(identifier)):[2209.06833](https://arxiv.org/abs/2209.06833). [Bibcode](/source/Bibcode_(identifier)):[2023MNRAS.518.1057E](https://ui.adsabs.harvard.edu/abs/2023MNRAS.518.1057E). [doi](/source/Doi_(identifier)):[10.1093/mnras/stac3140](https://doi.org/10.1093%2Fmnras%2Fstac3140). [ISSN](/source/ISSN_(identifier)) [0035-8711](https://search.worldcat.org/issn/0035-8711).

1. **[^](#cite_ref-Tanikawa2022_7-0)** Tanikawa, Ataru; Hattori, Kohei; et al. (September 2022). ["Search for a Black Hole Binary in Gaia DR3 Astrometric Binary Stars with Spectroscopic Data"](https://doi.org/10.3847%2F1538-4357%2Facbf36). *[The Astrophysical Journal](/source/The_Astrophysical_Journal)*. **946** (2): 79. [arXiv](/source/ArXiv_(identifier)):[2209.05632](https://arxiv.org/abs/2209.05632). [Bibcode](/source/Bibcode_(identifier)):[2023ApJ...946...79T](https://ui.adsabs.harvard.edu/abs/2023ApJ...946...79T). [doi](/source/Doi_(identifier)):[10.3847/1538-4357/acbf36](https://doi.org/10.3847%2F1538-4357%2Facbf36).

v t e Constellation of Centaurus List of stars in Centaurus Centaurus in Chinese astronomy Stars Bayer α A (Rigil Kentaurus) B (Toliman) C (Proxima Centauri) β (Hadar) γ δ ε ζ (Leepwal) η θ (Menkent) ι (Kulou) κ λ μ ν (Heng) ξ1 ξ2 ο1 ο2 π ρ σ τ υ1 υ2 φ χ ψ x1 x2 C3 D E F G H J K M N Q Flamsteed 1 (i) 2 (g) 3 (k) 4 (h) Variable R T V Y RR SV SX BV DY UY V346 V553 V744 V752 V761 (a) V763 (C1) V766 V779 (Krzemiński's star) V803 V810 V816 (Przybylski's Star) V831 V842 V885 V886 V863 V1032 V1369 V1400 V1935 HR 4460 (A) 4466 (C2) 4499 4522 4523 4537 (j) 4546 (B) 4721 4748 (u) 4796 4817 (l) 4831 (w) 4874 (p) 4888 (e) 4889 (n) 4940 (f) 4979 4989 5006 (r) 5041 (m) 5089 (d) 5174 (z) 5222 (y) 5224 5241 5297 5358 (v) 5371 5471 (b) 5485 (c1) 5489 (c2) HD 97413 98176 100453 101581 101930 102117 (Uklun) 103197 107914 108236 109749 110113 113538 113766 114386 114729 115600 116434 (Matza) 117207 117618 (Dofida) 117939 120411 121228 121504 124448 (Popper's Star) 125072 125595 131399 Other 2MASS J1126−5003 2M1207 Gaia BH2 HD 131399 Ab PSR B1259−63 PSR J1311−3430 TOI-763 WASP-15 (Nyamien) WASP-41 WASP-42 WASP-167/KELT-13 Exoplanets 2M1207b b Centauri b HD 101930 b HD 102117 b (Leklsullun) HD 103197 b HD 109749 b HD 113538 b c HD 114386 b HD 114729 b HD 117207 b HD 117618 b (Noifasui) HD 121504 b HIP 65426 b (Najsakopajk) HIP 67522 b NGTS-13b Proxima Centauri b c d WASP-15b (Asye) Star clusters NGC 3766 4230 4507 5281 5286 5316 5460 5617 5662 Other IC 2944 ω Centauri Scorpius–Centaurus association Stock 16 Nebulae NGC 3918 5307 Other Boomerang Nebula Fleming 1 G292.0+1.8 G306.3-0.9 Gum 41 IC 2944 IRAS 13208−6020 RCW 79 RCW 86 Southern Crab Nebula SuWt 2 Galaxies NGC 3557 3568 3749 3783 4444 4603 4622 4650A 4683 4696 4706 4709 4729 4730 4743 4744 4909 4930 4945 4976 5011 A 5026 5064 5082 5090 5091 5102 5114 5121 5128 (Centaurus A) 5161 5206 5253 5266 5291 5398 5408 5419 5483 5516 Other ESO 269-57 ESO 325-4 ESO 383-76 ESO 444-46 Fourcade-Figueroa Object IC 3370 IC 4214 IC 4329A IRAS 13224−3809 J1144−4308 LEDA 677373 PKS 1144−379 PKS 1353−341 PKS 1424−418 Galaxy clusters Abell S740 Centaurus Cluster Shapley Supercluster Astronomical events GW190521 SN 185 SN 1895B (Z) SN 1972E SN 1986G J1407b SN 2019so Category

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Adapted from the Wikipedia article [Gaia BH2](https://en.wikipedia.org/wiki/Gaia_BH2) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Gaia_BH2?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.