Wolf 922
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Capricornus |
| Right ascension | 21h 31m 18.57s |
| Declination | −09° 47′ 26.5″ |
| Apparent magnitude (V) | 11.96 – 11.99 A: 12.66 B: 14.76 |
| Characteristics | |
| Spectral type | M4.0V + M |
| U−B color index | 1.231 |
| B−V color index | 1.664 |
| J−H color index | 0.615 |
| J−K color index | 0.937 |
| Variable type | BY Draconis variable |
| Astrometry | |
| Radial velocity (Rv) | −56.3336±0.0188 km/s |
| Proper motion (μ) | RA: 1246.510 mas/yr Dec.: −61.066 mas/yr |
| Parallax (π) | 125.3±0.3 mas |
| Distance | 26.03 ± 0.06 ly (7.98 ± 0.02 pc) |
| Absolute magnitude (MV) | 12.6 |
| Orbit | |
| Primary | Wolf 922 A |
| Companion | Wolf 922 B |
| Period (P) | 704.9±0.5 d |
| Semi-major axis (a) | 0.1448±0.0005″ |
| Eccentricity (e) | 0.390±0.002 |
| Inclination (i) | 49.8±0.4° |
| Longitude of the node (Ω) | 326.1±0.4° |
| Periastron epoch (T) | 51164.0±1.1 |
| Argument of periastron (ω) (secondary) | 8.7±0.5° |
| Semi-amplitude (K1) (primary) | 5.21±0.02 km/s |
| Semi-amplitude (K2) (secondary) | 9.4±0.1 km/s |
| Details | |
| Wolf 922 A | |
| Mass | 0.270±0.004 M☉ |
| Radius | 0.3 R☉ |
| Metallicity [Fe/H] | 0.3 dex |
| Rotational velocity (v sin i) | 10 km/s |
| Wolf 922 B | |
| Mass | 0.145±0.002 M☉ |
| Other designations | |
| BB Cap, NSV 13753, Gaia DR3 6894054664842632448, GJ 831, HIP 106255, CCDM J21313-0947AB, WDS J21313-0947AB, Ci 20 1288, G 26-7, LFT 1639, LHS 511, LPM 786, LTT 8556, NLTT 51428, PLX 5184, PM J21313-0947, PM 21286-1001, Wolf 922, TIC 71600113, TYC 5790-1233-1, GCRV 26194, GCRV 72228, GSC 05790-00182, 2MASS J21311859-0947263, WISEA J213119.47-094727.0 | |
| Database references | |
| SIMBAD | data |
Wolf 922, also designated Gliese 831, is a nearby binary star composed of two low-mass red dwarfs in the zodiac constellation of Capricornus, close to the border with Aquarius. It has an apparent magnitude that varies between 11.96 and 11.99, far too faint to be seen by the naked eye from Earth but observable using a telescope with an aperture of 51 millimetres (2.0 in) or larger. It is located approximately 26 light-years (8.0 pc) distant based on parallax measurements, and approaching the Solar System at a heliocentric radial velocity of −56.33 km/s.
In 1994, it was discovered to show long-term variations in brightness by Edward W. Weis at the Van Vleck Observatory. It was given the variable-star designation BB Capricorni and classified as a BY Draconis variable in 1997.