Epsilon Librae

Epsilon Librae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
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]
Distance102 ± 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
Mass1.17±0.02[6] M☉
Radius1.5[9] R☉
Luminosity9.3[10] L☉
Surface gravity (log g)4.13[10] cgs
Temperature6,552±80[6] K
Metallicity [Fe/H]+0.09[10] dex
Rotational velocity (v sin i)10[5] km/s
Age1.5[10] Gyr
ε Lib B
Mass0.410±0.004[6] M☉
Other designations
ε Lib, 31 Lib, BD−09° 4138, HD 137052, HIP 75379, HR 5723, SAO 159234.[11]
Database references
SIMBADdata

Epsilon Librae (ε Lib) is the Bayer designation for a binary star system in the zodiac constellation Libra. 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.

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 an estimated 1.17[6] times the mass of the Sun and 1.5 times the Sun's radius. It is around 1.5[10] billion years old and is spinning with a projected rotational velocity of 10[5] km/s. The star radiates 9.3[10] times the solar luminosity 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]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Celis1975 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Houk1999 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Malaroda1975 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Takeda2005 was invoked but never defined (see the help page).
  6. ^ a b c d e f g h Cite error: The named reference Katoh2013 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Jancart2005 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Pourbaix2004 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference PasinettiFracassini2001 was invoked but never defined (see the help page).
  10. ^ a b c d e f Cite error: The named reference Takeda2007 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).