Epsilon Librae
Star in the constellation Libra
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Epsilon Librae is a binary star system in the zodiac constellation Libra. Its name is a Bayer designation that is Latinized from ε Librae, and abbreviated Epsilon Lib or ε Lib. With an apparent visual magnitude of 4.922,[2] it is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 32.02 mas,[1] it is located about 102 light years away from the Sun.
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Libra |
| Right ascension | 15h 24m 11.89101s[1] |
| Declination | −10° 19′ 20.1740″[1] |
| Apparent magnitude (V) | 4.922[2] |
| Characteristics | |
| Spectral type | F3 V[3] or F5 IV[4] |
| U−B color index | +0.080[2] |
| B−V color index | +0.451[2] |
| Astrometry | |
| Proper motion (μ) | RA: −66.52[1] mas/yr Dec.: −154.24[1] mas/yr |
| Parallax (π) | 32.02±0.72 mas[1] |
| Distance | 102 ± 2 ly (31.2 ± 0.7 pc) |
| Absolute magnitude (MV) | 2.37[5] |
| Orbit[6] | |
| Period (P) | 226.9437±0.0025 d |
| Semi-major axis (a) | 0.85192±0.00359 au |
| Eccentricity (e) | 0.6649±0.0014 |
| Inclination (i) | 52.6±9.4[7]° |
| Periastron epoch (T) | 2453593.022 ± 0.041 HJD[8] |
| Argument of periastron (ω) (secondary) | 339.84±0.15° |
| Details | |
| ε Lib A | |
| Mass | 1.17±0.02[6] M☉ |
| Radius | 2.159[9] R☉ |
| Luminosity | 9.3[10] L☉ |
| Surface gravity (log g) | 4.13[10] cgs |
| Temperature | 6,552±80[6] K |
| Metallicity [Fe/H] | +0.09[10] dex |
| Rotational velocity (v sin i) | 10[5] km/s |
| Age | 1.5[10] Gyr |
| ε Lib B | |
| Mass | 0.410±0.004[6] M☉ |
| Other designations | |
| ε Lib, 31 Lib, BD−09°4138, HD 137052, HIP 75379, HR 5723, SAO 159234[11] | |
| Database references | |
| SIMBAD | data |
This is a single-lined spectroscopic binary star system. The pair orbit each other with a period of 226.9 days and an eccentricity of 0.66.[6] The semimajor axis of their orbit is estimated to be 0.85 AU, or 85% of the distance from the Earth to the Sun. The primary, component A, has been catalogued with stellar classifications of F3 V[3] and F5 IV,[4] suggesting that it is an F-type star that either belongs to the main sequence or has evolved into a subgiant as the hydrogen at its core nears exhaustion.
The primary has 1.17 times the mass of the Sun[6] and 2.16 times the Sun's radius.[9] It is around 1.5 billion years old[10] and is spinning with a projected rotational velocity of 10[5] km/s. The star radiates 9.3 times the solar luminosity[10] from its outer atmosphere at an effective temperature of 6,552 K.[6] The secondary, component B, has 41% of the Sun's mass.[6]