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θ Librae
	Location of θ Librae (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Libra
Right ascension	15h 53m 49.53806s
Declination	–16° 43′ 45.4582″
Apparent magnitude (V)	4.136
Characteristics
Spectral type	G9IIIb
U−B color index	+0.82
B−V color index	+1.01
Astrometry
Radial velocity (Rv)	4.56±0.25 km/s
Proper motion (μ)	RA: +100.33 mas/yr ; Dec.: +135.02 mas/yr
Parallax (π)	19.36 ± 0.15 mas
Distance	168 ± 1 ly ; (51.7 ± 0.4 pc)
Absolute magnitude (MV)	0.665
Details
Mass	1.47 M☉
Radius	12.27 R☉
Luminosity	68.1 L☉
Surface gravity (log g)	2.44 cgs
Temperature	4,739 K
Metallicity [Fe/H]	–0.35 dex
Rotational velocity (v sin i)	0.0 km/s
Age	3.4 Gyr
Other designations
	θ Lib, 46 Librae, BD−16°4174, HD 142198, HIP 77853, HR 5908, SAO 159563
Database references
SIMBAD	data

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]

References

^ ^a ^b ^c ^d Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
^ ^a ^b ^c ^d Liu, Y. J.; et al. (2007). "The abundances of nearby red clump giants". Monthly Notices of the Royal Astronomical Society. 382 (2): 553–66. Bibcode:2007MNRAS.382..553L. doi:10.1111/j.1365-2966.2007.11852.x.
^ ^a ^b Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
^ ^a ^b Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
^ ^a ^b ^c Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209, S2CID 121883397
^ van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Reffert, Sabine; Bergmann, Christoph; Quirrenbach, Andreas; Trifonov, Trifon; Künstler, Andreas (2015). "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity". Astronomy and Astrophysics. 574: A116. arXiv:1412.4634. Bibcode:2015A&A...574A.116R. doi:10.1051/0004-6361/201322360. S2CID 59334290.
^ "tet Lib". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-19.
^ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
^ Edwards, D. A.; et al. (April 1980). "Photoelectric observations of lunar occultations. XI". Astronomical Journal. 85: 478–489. Bibcode:1980AJ.....85..478E. doi:10.1086/112700.
^ Thorén, P.; Edvardsson, B.; Gustafsson, B. (2004). "Subgiants as probes of galactic chemical evolution". Astronomy and Astrophysics. 425: 187–206. arXiv:astro-ph/0407260. Bibcode:2004A&A...425..187T. doi:10.1051/0004-6361:20040421. S2CID 2116895.