HR 5171
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus |
| A | |
| Right ascension | 13h 47m 10.864s |
| Declination | −62° 35′ 22.95″ |
| Apparent magnitude (V) | 6.1 – 7.5 |
| B | |
| Right ascension | 13h 47m 09.953s |
| Declination | −62° 35′ 15.99″ |
| Apparent magnitude (V) | 9.83 |
| Characteristics | |
| A | |
| Spectral type | K0 0-Ia |
| B−V color index | +2.499 |
| Variable type | EB + SDOR? |
| B | |
| Spectral type | B0 Ibp |
| B−V color index | +0.39 |
| Astrometry | |
| Radial velocity (Rv) | −38.20 km/s |
| Distance | 9,630+300 −310 ly (2,953+92 −96 pc) |
| A | |
| Proper motion (μ) | RA: −5.648 mas/yr Dec.: −1.797 mas/yr |
| Parallax (π) | 0.2459±0.0514 mas |
| Distance | approx. 13,000 ly (approx. 4,100 pc) |
| Absolute magnitude (MV) | −9.2 |
| B | |
| Proper motion (μ) | RA: −5.715 mas/yr Dec.: −2.143 mas/yr |
| Parallax (π) | 0.3257±0.0126 mas |
| Distance | 10,000 ± 400 ly (3,100 ± 100 pc) |
| Absolute magnitude (MV) | −5.8 |
| Orbit | |
| Primary | Aa |
| Name | Ab (disputed) |
| Period (P) | 1,304±6 days |
| Semi-major axis (a) | 2,028 - 2,195 R☉ |
| Eccentricity (e) | 0 |
| Inclination (i) | >60° |
| Details | |
| Aa | |
| Mass | 27 – 36 M☉ |
| Radius | 1,315 – 1,575 R☉ |
| Luminosity | 630,000+60,000 −55,000 L☉ |
| Surface gravity (log g) | −0.5±0.6 cgs |
| Temperature | 4,290±760 K |
| Age | 3.5 Myr |
| Ab (disputed) | |
| Mass | 5+15 −3 M☉ |
| Radius | 312 - 401, 650±150 R☉ |
| Temperature | 4,800 – 5,200 K |
| B | |
| Radius | 20 R☉ |
| Luminosity | 160,000 L☉ |
| Surface gravity (log g) | 3.0 – 3.5 cgs |
| Temperature | 26,000 K |
| Age | 4 Myr |
| Other designations | |
| V766 Cen, AAVSO 1340-62, CD−61°3988, HD 119796, HIP 67261, HR 5171, SAO 252448, WDS J13472-6235 | |
| Database references | |
| SIMBAD | data |
HR 5171, also known as V766 Centauri, is a multiple star system in the constellation Centaurus. The primary star is said to be either an extreme red supergiant (RSG) or recent post-red supergiant (Post-RSG) yellow hypergiant (YHG), both of which suggest it is one of the largest known stars. The star's diameter is uncertain but likely to be between 1,300 and 1,600 times that of the Sun. It is around 3 kiloparsecs (10,000 light-years) from Earth. It is a variable star, and when it is near its maximum brightness, magnitude 6.1, it is faintly visible to the naked eye under excellent observing conditions.
A 2014 publication hypothesized the star to be a contact binary, sharing a common envelope of material with a smaller yellow supergiant and secondary star, the two orbiting each other every 1,304±6 d. However, a 2019 publication ruled out this hypothesis.
An optical companion, HR 5171B, may or may not be at the same distance as the yellow hypergiant.