Binary star in the constellation Orion From Wikipedia, the free encyclopedia
31 Orionis is a binary star[3] system in the equatorial constellation of Orion, located near the bright star Mintaka. It is visible to the naked eye as a faint, orange-hued point of light with a baseline apparent visual magnitude of 4.71.[2] The distance to this system is approximately 490 light years away based on parallax,[1] and it is drifting further away with a mean radial velocity of +6 km/s.[1]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion |
| Right ascension | 05h 29m 43.98147s[1] |
| Declination | −01° 05′ 32.0582″[1] |
| Apparent magnitude (V) | 4.71[2] + 10.2[3] |
| Characteristics | |
| Spectral type | K5III[4] + F7V[3] |
| U−B color index | +1.91[5] |
| B−V color index | +1.58[5] |
| Variable type | SR?[6][7] |
| Astrometry | |
| Radial velocity (Rv) | +6.02±0.15[1] km/s |
| Proper motion (μ) | RA: +1.242[1] mas/yr Dec.: −25.476[1] mas/yr |
| Parallax (π) | 6.6135 ± 0.2293 mas[1] |
| Distance | 490 ± 20 ly (151 ± 5 pc) |
| Absolute magnitude (MV) | −1.23[2] |
| Details | |
| 31 Ori A | |
| Mass | 5.2[8] M☉ |
| Radius | 62[8] R☉ |
| Luminosity | 1,361[8] L☉ |
| Surface gravity (log g) | 0.92[8] cgs |
| Temperature | 4,610[8] K |
| Metallicity [Fe/H] | −0.21[2] dex |
| Rotational velocity (v sin i) | 2.7[9] km/s |
| 31 Ori B | |
| Mass | 1.1[10] M☉ |
| Radius | 1.2[10] R☉ |
| Luminosity | 1.9[10] L☉ |
| Surface gravity (log g) | 4.24[10] cgs |
| Temperature | 6,111[10] K |
| Metallicity [Fe/H] | −0.23[10] dex |
| Age | 3.9[10] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
As of 2008, the pair had an angular separation of 12.7″.[3] The brighter member, designated component A, is an aging giant star with a stellar classification of K5III.[4] It is reported as a semi-regular variable with magnitude ranging from 4.68 to 4.72 over 141 days,[6] although the General Catalogue of Variable Stars describes this as unconfirmed by subsequent observations.[7] It has the variable star designation CI Orionis, while 31 Orionis is the Flamsteed designation. The magnitude 10.2 companion star, component B, is an F-type main-sequence star with a class of F7V.[3]
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