Chi2 Orionis
Chi2 Orionis (Chi2 Ori / χ2 Orionis / χ2 Ori) /kaɪ.tuːˈɒraɪ/ is a B-type supergiant star in the constellation of Orion. It has an apparent visual magnitude of 4.63 but being quite distant, and heavily extinguished it burns with the greatest absolute visual light magnitude among stars in Orion within the near reaches of the galaxy, 0.9 of a magnitude brighter than Rigel. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is considered to be a member of the Gemini OB1 association.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Orion |
| Right ascension | 06h 03m 55.18437s |
| Declination | +20° 08′ 18.4281″ |
| Apparent magnitude (V) | 4.63 |
| Characteristics | |
| Spectral type | B2Ia |
| U−B color index | −0.68 |
| B−V color index | +0.28 |
| R−I color index | +0.22 |
| Variable type | α Cyg |
| Astrometry | |
| Radial velocity (Rv) | 16.8±0.9 km/s |
| Proper motion (μ) | RA: 2.679 mas/yr Dec.: −2.500 mas/yr |
| Parallax (π) | 0.7636 ± 0.1219 mas |
| Distance | approx. 4,300 ly (approx. 1,300 pc) |
| Absolute magnitude (MV) | −7.6 |
| Details | |
| Mass | 42.3±1.0 M☉ |
| Radius | 61.9 R☉ |
| Luminosity | 446,000 L☉ |
| Surface gravity (log g) | 2.35 cgs |
| Temperature | 19,000 K |
| Rotational velocity (v sin i) | 72 km/s |
| Age | 5±0.6 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
In apparent brightness it ranks, within Orion, admitting the higher published mean brightness of much more variable stars ranked above it, 35th.
Chi1 Orionis is an unrelated, yellow, main sequence star over two degrees away.