# 49 Librae

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Star in the constellation Libra

49 Librae Observation data Epoch J2000 Equinox J2000 Constellation Libra Right ascension 16h 00m 19.61087s[1] Declination −16° 32′ 00.5483″[1] Apparent magnitude (V) 5.47[2] Characteristics 49 Lib Aa Evolutionary stage Blue straggler[3] Spectral type F8 V[4] U−B color index +0.03[2] B−V color index +0.52[2] 49 Lib Ab Evolutionary stage White dwarf[3] Astrometry Radial velocity (Rv) −20.1±4.0[5] km/s Proper motion (μ) RA: −644.387[1] mas/yr Dec.: −360.803[1] mas/yr Parallax (π) 34.2281±0.1906 mas[1] Distance 95.3 ± 0.5 ly (29.2 ± 0.2 pc) Absolute magnitude (MV) 2.89[5] Orbit[4] Period (P) 1,142.4±1.1 d Semi-major axis (a) 2.72 AU[3] Eccentricity (e) 0.110±0.012 Inclination (i) 141.3+1.0 −2.0[3]° Longitude of the node (Ω) 163.5±2.8° Periastron epoch (T) 57,025±22 MJD Argument of periastron (ω) (secondary) 69.4±7.4° Semi-amplitude (K1) (primary) 3.847±0.051 km/s Details 49 Lib Aa Mass 1.55+0.07 −0.13[3] M☉ Radius 1.86+0.05 −0.04[1] R☉ Luminosity 4.74±0.03[1] L☉ Surface gravity (log g) 3.93±0.10[3] cgs Temperature 6,190±80[3] K Metallicity [Fe/H] −0.02[5] dex Rotational velocity (v sin i) 9.2±0.4[3] km/s Age 12±1[3] Gyr 49 Lib Ab Mass 0.50+0.03 −0.04[3] M☉ Other designations 49 Lib, BD−16°4196, FK5 1419, GJ 3931, HD 143333, HIP 78400, HR 5954, SAO 159625, WDS J16003-1632A[6] Database references SIMBAD data

**49 Librae** is a [binary star](/source/Binary_star)[7] system in the [Zodiac](/source/Zodiac) [constellation](/source/Constellation) of [Libra](/source/Libra_(constellation)). It has an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 5.47,[2] making it [faintly visible](/source/Bortle_scale) to the naked eye from dark suburban skies as a dim, yellow-white-hued star. The system is located 95 [light-years](/source/Light-year) away from the Sun, based on [parallax](/source/Stellar_parallax),[1] but is drifting closer with a [radial velocity](/source/Radial_velocity) of −20 km/s.[5]

The [Bayer designation](/source/Bayer_designation) [Phi Scorpii](/source/Phi_Scorpii) has been associated with this star. No star is found at the position marked φ Scorpii in [Johann Bayer](/source/Johann_Bayer)'s *[Uranometria](/source/Uranometria)*.[8] The closest stars to that position are 48 and 49 Librae; [48 Librae](/source/48_Librae) is clearly shown but not given a designation while no star is shown at the position of 49 Librae. In his Uranographia [Bode](/source/Johann_Elert_Bode) assigned the designation φ Scorpii to the star now known as 49 Librae.[9] The designation is no longer in use.[10]

## Characteristics

This is a single-lined [spectroscopic binary](/source/Spectroscopic_binary) system, first spotted to have a variable radial velocity by [W. S. Adams](/source/Walter_Sydney_Adams) in 1924. Both stars take 3.128 years to orbit around the system's [center of mass](/source/Center_of_mass) and have a rather low an [eccentricity](/source/Orbital_eccentricity) of 0.11.[4]

The primary component has a [stellar classification](/source/Stellar_classification) of F8 V or F9 V,[4] which at first would indicate it is an [F-type main-sequence star](/source/F-type_main-sequence_star). Such star would have an age around 2.3 billion years, consistent with a [Population I star](/source/Population_I_star). However, the [space velocity](/source/Stellar_kinematics) and chemical composition of this star is inconsistent with that of a Pop I star, indicating it is a much older (over 12 billion years) [Population II star](/source/Population_II_star). To account for its [evolutionary stage](/source/Stellar_evolution), which is too young for such age, it has been proposed 49 Lib A is a [blue straggler](/source/Blue_straggler) that was once smaller but gained mass after interacting gravitationally with the secondary.[3]

The secondary is a [white dwarf](/source/White_dwarf) with half the mass of the Sun.[3] The system is a source for radio and X-ray emissions, which may be coming from the secondary companion.[11]

## Evolution

Initially both components were [G-type main-sequence stars](/source/G-type_main-sequence_star) separated by 1.50 AU. The primary had a mass of 1.00±0.03 *M*☉, while the secondary had 1.05±0.02 *M*☉. [3]

The stars then started to evolve, becoming [red giants](/source/Red_giant). [Mass transfer](/source/Mass_transfer) between components started to happen. The end product was the secondary becoming the current white dwarf with half of its original mass, and the primary gaining 0.55 M☉ and becoming a F-type star.[3]

Within 500 million years, the primary will evolve and 49 Librae may become a double white-dwarf system. However, if the secondary accrete sufficient mass during the process, the system may instead undergo a [Type Ia supernova](/source/Type_Ia_supernova).[3]

## See also

- [List of supernova candidates](/source/List_of_supernova_candidates)

## References

1. ^ [***a***](#cite_ref-GaiaDR2_1-0) [***b***](#cite_ref-GaiaDR2_1-1) [***c***](#cite_ref-GaiaDR2_1-2) [***d***](#cite_ref-GaiaDR2_1-3) [***e***](#cite_ref-GaiaDR2_1-4) [***f***](#cite_ref-GaiaDR2_1-5) [***g***](#cite_ref-GaiaDR2_1-6) [***h***](#cite_ref-GaiaDR2_1-7) [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051). [Gaia DR2 record for this source](https://vizier.u-strasbg.fr/viz-bin/VizieR-S?Gaia%20DR2%206250364583301188864) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-aaass34_1_2-0) [***b***](#cite_ref-aaass34_1_2-1) [***c***](#cite_ref-aaass34_1_2-2) [***d***](#cite_ref-aaass34_1_2-3) Nicolet, B. (October 1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", *Astronomy and Astrophysics Supplement Series*, **34**: 1–49, [Bibcode](/source/Bibcode_(identifier)):[1978A&AS...34....1N](https://ui.adsabs.harvard.edu/abs/1978A&AS...34....1N).

1. ^ [***a***](#cite_ref-Fuhrmann2017_3-0) [***b***](#cite_ref-Fuhrmann2017_3-1) [***c***](#cite_ref-Fuhrmann2017_3-2) [***d***](#cite_ref-Fuhrmann2017_3-3) [***e***](#cite_ref-Fuhrmann2017_3-4) [***f***](#cite_ref-Fuhrmann2017_3-5) [***g***](#cite_ref-Fuhrmann2017_3-6) [***h***](#cite_ref-Fuhrmann2017_3-7) [***i***](#cite_ref-Fuhrmann2017_3-8) [***j***](#cite_ref-Fuhrmann2017_3-9) [***k***](#cite_ref-Fuhrmann2017_3-10) [***l***](#cite_ref-Fuhrmann2017_3-11) [***m***](#cite_ref-Fuhrmann2017_3-12) [***n***](#cite_ref-Fuhrmann2017_3-13) [***o***](#cite_ref-Fuhrmann2017_3-14) Fuhrmann, K.; Chini, R. (January 2, 2017), "Bright Times for an Ancient Star", *The Astrophysical Journal*, **834** (2): 114, [Bibcode](/source/Bibcode_(identifier)):[2017ApJ...834..114F](https://ui.adsabs.harvard.edu/abs/2017ApJ...834..114F), [doi](/source/Doi_(identifier)):[10.3847/1538-4357/834/2/114](https://doi.org/10.3847%2F1538-4357%2F834%2F2%2F114), [S2CID](/source/S2CID_(identifier)) [125888005](https://api.semanticscholar.org/CorpusID:125888005).

1. ^ [***a***](#cite_ref-Willmarth2016_4-0) [***b***](#cite_ref-Willmarth2016_4-1) [***c***](#cite_ref-Willmarth2016_4-2) [***d***](#cite_ref-Willmarth2016_4-3) Willmarth, Daryl W.; et al. (August 2016), ["Spectroscopic Orbits for 15 Late-type Stars"](https://dipot.ulb.ac.be/dspace/bitstream/2013/236718/3/Willmarth_2016_AJ_152_46.pdf) (PDF), *The Astronomical Journal*, **152** (2): 13, [Bibcode](/source/Bibcode_(identifier)):[2016AJ....152...46W](https://ui.adsabs.harvard.edu/abs/2016AJ....152...46W), [doi](/source/Doi_(identifier)):[10.3847/0004-6256/152/2/46](https://doi.org/10.3847%2F0004-6256%2F152%2F2%2F46), [S2CID](/source/S2CID_(identifier)) [53648490](https://api.semanticscholar.org/CorpusID:53648490), 46.

1. ^ [***a***](#cite_ref-aaa475_2_519_5-0) [***b***](#cite_ref-aaa475_2_519_5-1) [***c***](#cite_ref-aaa475_2_519_5-2) [***d***](#cite_ref-aaa475_2_519_5-3) Nordström, B.; et al. (November 2007), "The Geneva-Copenhagen survey of the Solar neighbourhood. II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk", *Astronomy & Astrophysics*, **475** (2): 519–537, [arXiv](/source/ArXiv_(identifier)):[0707.1891](https://arxiv.org/abs/0707.1891), [Bibcode](/source/Bibcode_(identifier)):[2007A&A...475..519H](https://ui.adsabs.harvard.edu/abs/2007A&A...475..519H), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20077221](https://doi.org/10.1051%2F0004-6361%3A20077221), [S2CID](/source/S2CID_(identifier)) [119054949](https://api.semanticscholar.org/CorpusID:119054949).

1. **[^](#cite_ref-SIMBAD_6-0)** ["49 Lib"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=49+Lib). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2013-11-06.

1. **[^](#cite_ref-apjs180_1_117_7-0)** Abt, Helmut A. (January 2009), "MK Classifications of Spectroscopic Binaries", *The Astrophysical Journal Supplement*, **180** (1): 117–118, [Bibcode](/source/Bibcode_(identifier)):[2009ApJS..180..117A](https://ui.adsabs.harvard.edu/abs/2009ApJS..180..117A), [doi](/source/Doi_(identifier)):[10.1088/0067-0049/180/1/117](https://doi.org/10.1088%2F0067-0049%2F180%2F1%2F117), [S2CID](/source/S2CID_(identifier)) [122811461](https://api.semanticscholar.org/CorpusID:122811461).

1. **[^](#cite_ref-bayer_8-0)** Bayer, Johann; Mair, Alexander (1603). [*Uranometria*](https://books.google.com/books?id=5NrCIF5mnysC&dq=bayer+uranometria&pg=IA1) (in Latin). Excvdit Christophorvs Mangvs. Retrieved 2025-11-10.

1. **[^](#cite_ref-startales_9-0)** [Ridpath, Ian](/source/Ian_Ridpath). ["Scorpius"](http://www.ianridpath.com/startales/scorpius.html). *Star Tales*. Retrieved 2025-09-10.

1. **[^](#cite_ref-kaler-sco_10-0)** ["Chi and Psi Scorpii"](http://stars.astro.illinois.edu/sow/chisco.html), *stars.astro.illinois.edu*, retrieved 2025-07-13.

1. **[^](#cite_ref-Lazio2010_11-0)** Lazio, T. Joseph W.; et al. (January 2010), "A Blind Search for Magnetospheric Emissions from Planetary Companions to Nearby Solar-Type Stars", *The Astronomical Journal*, **139** (1): 96–101, [arXiv](/source/ArXiv_(identifier)):[0910.3938](https://arxiv.org/abs/0910.3938), [Bibcode](/source/Bibcode_(identifier)):[2010AJ....139...96L](https://ui.adsabs.harvard.edu/abs/2010AJ....139...96L), [doi](/source/Doi_(identifier)):[10.1088/0004-6256/139/1/96](https://doi.org/10.1088%2F0004-6256%2F139%2F1%2F96), [S2CID](/source/S2CID_(identifier)) [118537554](https://api.semanticscholar.org/CorpusID:118537554).

v t e Constellation of Libra List of stars in Libra Libra in Chinese astronomy Stars Bayer α1 α2 (Zubenelgenubi) β (Zubeneschamali) γ (Zubenelhakrabi) δ ε ζ1 ζ2 ζ3 ζ4 η θ ι1 ι2 κ λ μ ν ξ1 ξ2 ο σ (Brachium) τ υ Flamsteed 2 3 4 5 10 11 12 16 17 18 22 23 26 28 30 36 37 41 42 47 48 49 50 Variable HN HO KU KX HR 5504 5455 HD 133131 134439 134440 135485 137010 139139 140283 141569 141937 Other 2M1510 2MASS 1507−1627 CWISEP J1446−2317 HE 1523−0901 WASP-57 WISE 1534−1043 WISE 1541−2250 Exoplanets 23 Librae b c Gliese 581b c e HD 137010 b (unconfirmed) K2-315b WASP-189b Star clusters NGC 5897 Galaxies NGC 5597 5605 5716 5728 5792 5793 5861 5885 5890 5898 5915 5917 Other AP Librae IC 1059 IRAS 14348−1447 PKS 1510−089 PKS 1519−273 QSO B1524−136 RXC J1504.1−0248 BCG Category

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Adapted from the Wikipedia article [49 Librae](https://en.wikipedia.org/wiki/49_Librae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/49_Librae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.