Sigma Librae
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Libra |
| Right ascension | 15h 04m 04.21480s |
| Declination | −25° 16′ 55.0905″ |
| Apparent magnitude (V) | 3.20 - 3.46 |
| Characteristics | |
| Spectral type | M2.5III |
| U−B color index | +1.94 |
| B−V color index | +1.70 |
| Variable type | SRb |
| Astrometry | |
| Radial velocity (Rv) | −4.2 km/s |
| Proper motion (μ) | RA: −73.484 mas/yr Dec.: −42.632 mas/yr |
| Parallax (π) | 12.539±0.3 mas |
| Distance | 261.0+5.25 −6.26 ly (80.02+1.61 −1.92 pc) |
| Absolute magnitude (MV) | −1.5 |
| Details | |
| Mass | 1.9±0.2 M☉ |
| Radius | 108±3 R☉ |
| Luminosity | 1,800 L☉ |
| Surface gravity (log g) | 0.9±0.3 cgs |
| Temperature | 3,596 K |
| Metallicity [Fe/H] | 0.00 dex |
| Other designations | |
| Brachium, 20 Librae, CD−24 11834, FK5 556, HD 133216, HIP 73714, HR 5603, SAO 183139., WDS 15041-2517 | |
| Database references | |
| SIMBAD | data |
Sigma Librae (σ Librae, abbreviated Sigma Lib, σ Lib) is a binary star in the constellation of Libra. The apparent visual magnitude is +3.29, making it visible to the naked eye. Based upon parallax measurements, this system is at a distance of roughly 260 light-years (80 parsecs) from the Sun, with a 2% margin of error. At that distance, the visual magnitude is diminished by 0.20±0.17 from extinction caused by intervening gas and dust.
The two components are designated Sigma Librae A (officially named Brachium /ˈbreɪkiəm/, the traditional name for the system) and B.