Gaia BH2

Gaia BH2

DECaPS image of Gaia BH2 (star at the center)
Observation data
Epoch J2000      Equinox J2000
Constellation Centaurus
Right ascension 13h 50m 16.748s[1]
Declination −59° 14′ 20.33″[1]
Apparent magnitude (V) 12.711[2]
Characteristics
Red giant
Evolutionary stage Red giant
Black hole
Evolutionary stage Stellar black hole
Astrometry
Radial velocity (Rv)−5.04±2.08[1] km/s
Proper motion (μ) RA: −10.48±0.1 mas/yr[3]
Dec.: −4.61±0.06 mas/yr[3]
Parallax (π)0.859 ± 0.018 mas[3]
Distance3,800 ± 80 ly
(1,160 ± 20 pc)
Orbit[3]
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[3]
Red giant
Mass1.07±0.19 M☉
Radius7.77±0.25 R☉
Luminosity (bolometric)24.6±1.6 L☉
Surface gravity (log g)2.71±0.24 cgs
Temperature4,604±87 K
Metallicity [Fe/H]−0.22±0.02 dex
Rotational velocity (v sin i)<1.5 km/s
Black hole
Mass8.94±0.34 M☉
Other designations
Gaia BH2, UCAC4 154-126202, 2MASS J13501675-5914203, Gaia DR3 5870569352746779008
Database references
SIMBADdata

Gaia BH2 (Gaia DR3 5870569352746779008) is a binary system consisting of a red giant and what is very likely 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.[3]

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 1.07 M☉ and a radius of 7.77 R☉. Its temperature is estimated at 4,604 K (4,331 °C; 7,828 °F).[3]

  1. ^ a b c Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference ucac4 was invoked but never defined (see the help page).
  3. ^ a b c d e f Cite error: The named reference elbadry was invoked but never defined (see the help page).