Gaia BH2
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 13h 50m 16.748s |
| Declination | −59° 14′ 20.33″ |
| Apparent magnitude (V) | 12.711 |
| Characteristics | |
| Red giant | |
| Evolutionary stage | Red giant |
| Black hole | |
| Evolutionary stage | Stellar black hole |
| Astrometry | |
| Radial velocity (Rv) | −5.04±2.08 km/s |
| Proper motion (μ) | RA: −10.48±0.1 mas/yr Dec.: −4.61±0.06 mas/yr |
| Parallax (π) | 0.859±0.018 mas |
| Distance | 3,800 ± 80 ly (1,160 ± 20 pc) |
| Orbit | |
| 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 M☉ |
| Radius | 8.55+0.20 −0.15 R☉ |
| Luminosity (bolometric) | 24.6±1.6 L☉ |
| Surface gravity (log g) | 2.71±0.24 cgs |
| Temperature | 4,604±87 K |
| Metallicity [Fe/H] | −0.22±0.02 dex |
| Rotation | 398±5 days (preliminary estimate) |
| Rotational velocity (v sin i) | <1.5 km/s |
| Age | 5.1+1.2 −1.8 Gyr |
| Black hole | |
| Mass | 8.94±0.34 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 consisting of a red giant and a stellar-mass black hole. Gaia BH2 is located about 3,800 light years away (1.16 kpc away) in the constellation of Centaurus, making it as of 2024 the third-closest known black hole system to Earth. Gaia BH2 is the second black hole discovered from Gaia DR3 astrometric data.
The black hole and red giant orbit the system 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☉, which means its Schwarzschild radius should be about 26.4 km (16.4 mi). The red giant has a mass of 1.17 M☉ and a radius of 8.6 R☉. Its temperature is estimated at 4,604 K (4,331 °C; 7,828 °F). The star is enriched in alpha elements, thus is believed to have undergone mass transfer with another star.