Theta Librae

θ Librae
Location of θ Librae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Libra
Right ascension 15h 53m 49.53806s[1]
Declination –16° 43′ 45.4582″[1]
Apparent magnitude (V) 4.136[2]
Characteristics
Spectral type G9IIIb[3]
U−B color index +0.82[4]
B−V color index +1.01[4]
Astrometry
Radial velocity (Rv)4.56±0.25[5] km/s
Proper motion (μ) RA: +100.33[1] mas/yr
Dec.: +135.02[1] mas/yr
Parallax (π)19.36 ± 0.15 mas[6]
Distance168 ± 1 ly
(51.7 ± 0.4 pc)
Absolute magnitude (MV)0.665[2]
Details
Mass1.47[7] M☉
Radius12.27[7] R☉
Luminosity68.1[7] L☉
Surface gravity (log g)2.44[7] cgs
Temperature4,739[7] K
Metallicity [Fe/H]–0.35[7] dex
Rotational velocity (v sin i)0.0[5] km/s
Age3.4[7] Gyr
Other designations
θ Lib, 46 Librae, BD−16°4174, HD 142198, HIP 77853, HR 5908, SAO 159563[8]
Database references
SIMBADdata

θ Librae, Latinised as Theta Librae, is a single[9] star in the southern zodiac constellation of Libra, near the constellation border with Scorpius. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.14.[2] The distance to this star is approximately 168 light years, as determined by parallax, and it is drifting further away with a radial velocity of 5 km/s.[5] The position of this star near the ecliptic means it is subject to lunar occultations.[10]

This object is an aging giant star with a stellar classification of G9IIIb.[3] Having exhausted the supply of hydrogen at its core, it has cooled and expanded; at present it has 12.3 times the girth of the Sun.[7] The star has an estimated mass about 47% greater than the Sun. It is radiating about 68 times the luminosity of the Sun from its photosphere at an effective temperature of about 4,739 K.[7] It is probably on the red giant branch, which indicates it is generating energy through hydrogen fusion in a shell outside an inert helium core.[7] However, there is a 41% chance that it is a red clump giant on the horizontal branch,[2] which would mean it was somewhat older and less massive.[7] It has sometimes been classified spectroscopically as a subgiant, but detailed study shows that it is too cool and luminous to be on the subgiant branch.[11]

  1. ^ a b c d Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Liu2007 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Keenan1989 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference clpl99 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Massarotti2008 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  7. ^ a b c d e f g h i j k Cite error: The named reference reffert2015 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Edwards1980 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference thoren2004 was invoked but never defined (see the help page).