49 Librae
49 Librae is the Flamsteed designation for a binary star system in the Zodiac constellation of Libra. It has an apparent visual magnitude of 5.47, making it faintly visible to the naked eye from dark suburban skies as a dim, yellow-white hued star. The system is located 95 light years away from the Sun, based on parallax, but is drifting closer with a radial velocity of −20 km/s.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Libra |
| Right ascension | 16h 00m 19.61087s |
| Declination | –16° 32′ 00.5483″ |
| Apparent magnitude (V) | 5.47 |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | F8 V |
| U−B color index | +0.03 |
| B−V color index | +0.52 |
| Astrometry | |
| Radial velocity (Rv) | −20.1±4.0 km/s |
| Proper motion (μ) | RA: –644.387 mas/yr Dec.: –360.803 mas/yr |
| Parallax (π) | 34.2281 ± 0.1906 mas |
| Distance | 95.3 ± 0.5 ly (29.2 ± 0.2 pc) |
| Absolute magnitude (MV) | 2.89 |
| Orbit | |
| Period (P) | 1,142.4±1.1 d |
| Semi-major axis (a) | ≥ 59.53±0.244 Gm |
| Eccentricity (e) | 0.110±0.012 |
| Inclination (i) | 143.0±2.0° |
| Longitude of the node (Ω) | 163.5±2.8° |
| Periastron epoch (T) | 57025±22 MJD |
| Argument of periastron (ω) (secondary) | 69.4±7.4° |
| Semi-amplitude (K1) (primary) | 3.847±0.051 km/s |
| Details | |
| 49 Lib A | |
| Mass | 1.4 M☉ |
| Radius | 1.86+0.05 −0.04 R☉ |
| Luminosity | 4.74±0.03 L☉ |
| Surface gravity (log g) | 4.14 cgs |
| Temperature | 6,237 K |
| Metallicity [Fe/H] | –0.02 dex |
| Rotational velocity (v sin i) | 9.6±1.0 km/s |
| Age | 12 Gyr |
| 49 Lib B | |
| Mass | 0.45 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The variable nature of the velocity for 49 Librae was first noted by W. S. Adams in 1924. It is a single-lined spectroscopic binary with an orbital period of 3.128 years and an eccentricity of 0.11. The primary component has a stellar classification of F8 V or F9 V, indicating it is an F-type main-sequence star. It has an estimated 1.4 times the mass of the Sun, while the companion only has 0.4 solar masses. The system is a source for radio and X-ray emissions, which may be coming from the secondary companion.