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49 Librae
View on Wikipedia| 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[7] system in the Zodiac constellation of Libra. It has an apparent visual magnitude of 5.47,[2] making it faintly visible to the naked eye from dark suburban skies as a dim, yellow-white-hued star. The system is located 95 light-years away from the Sun, based on parallax,[1] but is drifting closer with a radial velocity of −20 km/s.[5]
The Bayer designation Phi Scorpii has been associated with this star. No star is found at the position marked φ Scorpii in Johann Bayer's Uranometria.[8] The closest stars to that position are 48 and 49 Librae; 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 assigned the designation φ Scorpii to the star now known as 49 Librae.[9] The designation is no longer in use.[10]
Characteristics
[edit]This is a single-lined spectroscopic binary system, first spotted to have a variable radial velocity by W. S. Adams in 1924. Both stars take 3.128 years to orbit around the system's center of mass and have a rather low an eccentricity of 0.11.[4]
The primary component has a stellar classification of F8 V or F9 V,[4] which at first would indicate it is an F-type main-sequence star. Such star would have an age around 2.3 billion years, consistent with a Population I star. However, the space velocity 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. To account for its evolutionary stage, which is too young for such age, it has been proposed 49 Lib A is a blue straggler that was once smaller but gained mass after interacting gravitationally with the secondary.[3]
The secondary is a 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
[edit]Initially both components were G-type main-sequence stars 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. 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.[3]
References
[edit]- ^ a b c d e f g h 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 Nicolet, B. (October 1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
- ^ a b c d e f g h i j k l m n o Fuhrmann, K.; Chini, R. (January 2, 2017), "Bright Times for an Ancient Star", The Astrophysical Journal, 834 (2): 114, Bibcode:2017ApJ...834..114F, doi:10.3847/1538-4357/834/2/114, S2CID 125888005.
- ^ a b c d Willmarth, Daryl W.; et al. (August 2016), "Spectroscopic Orbits for 15 Late-type Stars" (PDF), The Astronomical Journal, 152 (2): 13, Bibcode:2016AJ....152...46W, doi:10.3847/0004-6256/152/2/46, S2CID 53648490, 46.
- ^ a b c d 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:0707.1891, Bibcode:2007A&A...475..519H, doi:10.1051/0004-6361:20077221, S2CID 119054949.
- ^ "49 Lib". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2013-11-06.
- ^ Abt, Helmut A. (January 2009), "MK Classifications of Spectroscopic Binaries", The Astrophysical Journal Supplement, 180 (1): 117–118, Bibcode:2009ApJS..180..117A, doi:10.1088/0067-0049/180/1/117, S2CID 122811461.
- ^ Bayer, Johann; Mair, Alexander (1603). Uranometria (in Latin). Excvdit Christophorvs Mangvs. Retrieved 2025-11-10.
- ^ Ridpath, Ian. "Scorpius". Star Tales. Retrieved 2025-09-10.
- ^ "Chi and Psi Scorpii", stars.astro.illinois.edu, retrieved 2025-07-13.
- ^ 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:0910.3938, Bibcode:2010AJ....139...96L, doi:10.1088/0004-6256/139/1/96, S2CID 118537554.
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