# Xi Lupi

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Triple star system in the constellation Lupus

Xi Lupi Location of ξ Lupi (circled in red) Observation data Epoch J2000.0 Equinox ICRS Constellation Lupus ξ1 Lup Right ascension 15h 56m 53.48964s[1] Declination −33° 57′ 58.0131″[1] Apparent magnitude (V) 5.114[2] ξ2 Lup Right ascension 15h 56m 54.11281s[3] Declination −33° 57′ 51.3380″[3] Apparent magnitude (V) 5.55[4] Characteristics ξ1 Lup Spectral type A3 V[5] U−B color index 0.069[2] B−V color index 0.116[2] ξ2 Lup Spectral type B9 V[5] B−V color index +0.06[4] Astrometry ξ1 Lup Radial velocity (Rv) −10.0±4.2[6] km/s Proper motion (μ) RA: +11.963 mas/yr[1] Dec.: −37.94 mas/yr[1] Parallax (π) 15.0230±0.1787 mas[1] Distance 217 ± 3 ly (66.6 ± 0.8 pc) ξ2 Lup Radial velocity (Rv) −12.20±1.78[6] km/s Proper motion (μ) RA: +10.663 mas/yr[3] Dec.: −41.073 mas/yr[3] Parallax (π) 15.5015±0.0722 mas[3] Distance 210.4 ± 1.0 ly (64.5 ± 0.3 pc) Details ξ1 Lup A Mass 2.0[7] M☉ Radius 2.0[7] R☉ Surface gravity (log g) 4.14±0.14[8] cgs Temperature 8,650[7] K Rotational velocity (v sin i) 78[8] km/s Age 450[7] Myr ξ1 Lup B Mass 1.65[7] M☉ Radius 1.6[7] R☉ Temperature 7,800[7] K Age 450[7] Myr ξ2 Lup Mass 2[7] M☉ Radius 1.74±0.04[9] R☉ Luminosity 22.7±1.0[9] L☉ Surface gravity (log g) 4.34±0.06[9] cgs Temperature 9,550±120[9] K Rotational velocity (v sin i) 184[8] km/s Age 500[7] Myr Other designations CCDM J15569-3358, WDS J15569-3358 A: ξ1 Lup, CD−33°10826A, HD 142629, HIP 78105, HR 5925, SAO 207144[10] B: ξ2 Lup, CD−33°10826B, HD 142630, HIP 78106, HR 5926, SAO 207145[11] Database references SIMBAD ξ1 Lup ξ2 Lup

**Xi Lupi** is a [triple star](/source/Triple_star) system[7] in the [southern](/source/Southern_celestial_hemisphere) [constellation](/source/Constellation) of [Lupus](/source/Lupus_(constellation)). Its main identifier is a [Bayer designation](/source/Bayer_designation) that is [Latinized](/source/Romanization_of_Greek) from ξ Lupi, and abbreviated Xi Lup or ξ Lup. The combined [apparent magnitude](/source/Apparent_magnitude) is 4.56, making it faintly visible to the [naked eye](/source/Naked_eye).[a] The system is located at 210 [light-years](/source/Light-year) (64 [parsecs](/source/Parsec)) from Earth, and is a member of the Upper Scorpius sub-group of the nearby [Sco OB2](/source/Sco_OB2) association.[12]

## Characteristics

This is a hierarchical triple system. It consists on the binary star ξ1 Lup and the star ξ2 Lup; both form a [visual binary](/source/Visual_binary) separated by 10.2" in the sky, or 660 [astronomical units](/source/Astronomical_unit) at their distance. The components of ξ1 Lup, named ξ1 Lup A and B, are separated by about the same distance Earth is from Sun (1 au), the orbital period is an estimated 200 days, although the observed separation is merely a [projected separation](/source/Projected_separation) and the whole orbit has not been observed.[7]

ξ1 Lup has a combined [stellar classification](/source/Stellar_classification) of A3 V,[5] and its primary and secondary components have, respectively, 2.0 and 1.65 times the [mass of the Sun](/source/Mass_of_the_Sun), radii 2.0 and 1.6 times solar and [effective temperatures](/source/Effective_temperature) of 8,650 and 7,850 [K](/source/Kelvin).[7]

ξ2 Lup has a stellar classification of B9 V,[5] matching a [B-type main-sequence star](/source/B-type_main-sequence_star). It has twice the mass of the Sun,[7] 1.74 times the [Sun's radius](/source/Sun's_radius), is 23 times more luminous and has an [effective temperature](/source/Effective_temperature) of 9,550 K.[9] It spins rapidly with a [projected rotational velocity](/source/Projected_rotational_velocity) of 184 [km/s](/source/Metre_per_second).[8] The star has a [peculiar velocity](/source/Peculiar_velocity) of 14.3±1.9 km/s relative to its neighbors, and is probably (86% chance) a [runaway star](/source/Runaway_star).[13]

The system is currently about 500 million years old. When ξ1 Lup A evolves into an [AGB star](/source/AGB_star), it will likely engulf component Ab, but given the orbit of the system is unknown, it may be more distant, and survive its companion's AGB phase. Assuming the Aa-Ab separation is correct, the system will likely end as a triple white dwarf system; few of such system have been observed so far.[7]

## Notes

1. **[^](#cite_ref-12)** Calculated from components' individual magnitudes using the equation given in [Apparent magnitude § Magnitude addition](/source/Apparent_magnitude#Magnitude_addition).

## References

1. ^ [***a***](#cite_ref-DR3a_1-0) [***b***](#cite_ref-DR3a_1-1) [***c***](#cite_ref-DR3a_1-2) [***d***](#cite_ref-DR3a_1-3) Vallenari, A.; et al. (Gaia collaboration) (2023), ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940), *Astronomy and Astrophysics*, **674**: A1, [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211), [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940), [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D6012174802400278016%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Slawson1992_2-0) [***b***](#cite_ref-Slawson1992_2-1) [***c***](#cite_ref-Slawson1992_2-2) Slawson, Robert W.; Hill, Robert J.; Landstreet, John D. (September 1992), "A homogeneous catalog of new UBV and H-beta photometry of B- and A-type stars in and around the Scorpius-Centaurus OB association", *Astrophysical Journal Supplement Series*, **82** (1): 117–144, [Bibcode](/source/Bibcode_(identifier)):[1992ApJS...82..117S](https://ui.adsabs.harvard.edu/abs/1992ApJS...82..117S), [doi](/source/Doi_(identifier)):[10.1086/191711](https://doi.org/10.1086%2F191711).

1. ^ [***a***](#cite_ref-DR3b_3-0) [***b***](#cite_ref-DR3b_3-1) [***c***](#cite_ref-DR3b_3-2) [***d***](#cite_ref-DR3b_3-3) Vallenari, A.; et al. (Gaia collaboration) (2023), ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940), *Astronomy and Astrophysics*, **674**: A1, [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211), [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940), [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D6012174836760016512%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-tycho2_4-0) [***b***](#cite_ref-tycho2_4-1) Høg, E.; et al. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", *Astronomy and Astrophysics*, **355**: L27, [Bibcode](/source/Bibcode_(identifier)):[2000A&A...355L..27H](https://ui.adsabs.harvard.edu/abs/2000A&A...355L..27H), [doi](/source/Doi_(identifier)):[10.1888/0333750888/2862](https://doi.org/10.1888%2F0333750888%2F2862).

1. ^ [***a***](#cite_ref-Levato1975_5-0) [***b***](#cite_ref-Levato1975_5-1) [***c***](#cite_ref-Levato1975_5-2) [***d***](#cite_ref-Levato1975_5-3) Levato, H. (January 1975), "Rotational velocities and spectral types for a sample of binary systems", *Astronomy and Astrophysics Supplement Series*, **19**: 91–99, [Bibcode](/source/Bibcode_(identifier)):[1975A&AS...19...91L](https://ui.adsabs.harvard.edu/abs/1975A&AS...19...91L).

1. ^ [***a***](#cite_ref-deBruijne2012_6-0) [***b***](#cite_ref-deBruijne2012_6-1) de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", *Astronomy & Astrophysics*, **546**: 14, [arXiv](/source/ArXiv_(identifier)):[1208.3048](https://arxiv.org/abs/1208.3048), [Bibcode](/source/Bibcode_(identifier)):[2012A&A...546A..61D](https://ui.adsabs.harvard.edu/abs/2012A&A...546A..61D), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201219219](https://doi.org/10.1051%2F0004-6361%2F201219219), [S2CID](/source/S2CID_(identifier)) [59451347](https://api.semanticscholar.org/CorpusID:59451347), A61.

1. ^ [***a***](#cite_ref-Waisberg2025_7-0) [***b***](#cite_ref-Waisberg2025_7-1) [***c***](#cite_ref-Waisberg2025_7-2) [***d***](#cite_ref-Waisberg2025_7-3) [***e***](#cite_ref-Waisberg2025_7-4) [***f***](#cite_ref-Waisberg2025_7-5) [***g***](#cite_ref-Waisberg2025_7-6) [***h***](#cite_ref-Waisberg2025_7-7) [***i***](#cite_ref-Waisberg2025_7-8) [***j***](#cite_ref-Waisberg2025_7-9) [***k***](#cite_ref-Waisberg2025_7-10) [***l***](#cite_ref-Waisberg2025_7-11) [***m***](#cite_ref-Waisberg2025_7-12) [***n***](#cite_ref-Waisberg2025_7-13) [***o***](#cite_ref-Waisberg2025_7-14) Waisberg, Idel; Klein, Ygal; Katz, Boaz (July 2025), "Hidden Companions to Intermediate-mass Stars. Upgraded Multiplicity 2 → 3. XXIX. Discovery of a 1.65 M☉, 1.0 au Companion to Xi1 Lupi", *Research Notes of the AAS*, **9** (7), [doi](/source/Doi_(identifier)):[10.3847/2515-5172/adefd9](https://doi.org/10.3847%2F2515-5172%2Fadefd9).

1. ^ [***a***](#cite_ref-David2015_8-0) [***b***](#cite_ref-David2015_8-1) [***c***](#cite_ref-David2015_8-2) [***d***](#cite_ref-David2015_8-3) David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", *The Astrophysical Journal*, **804** (2): 146, [arXiv](/source/ArXiv_(identifier)):[1501.03154](https://arxiv.org/abs/1501.03154), [Bibcode](/source/Bibcode_(identifier)):[2015ApJ...804..146D](https://ui.adsabs.harvard.edu/abs/2015ApJ...804..146D), [doi](/source/Doi_(identifier)):[10.1088/0004-637X/804/2/146](https://doi.org/10.1088%2F0004-637X%2F804%2F2%2F146), [S2CID](/source/S2CID_(identifier)) [33401607](https://api.semanticscholar.org/CorpusID:33401607).

1. ^ [***a***](#cite_ref-tic_9-0) [***b***](#cite_ref-tic_9-1) [***c***](#cite_ref-tic_9-2) [***d***](#cite_ref-tic_9-3) [***e***](#cite_ref-tic_9-4) Stassun, Keivan G.; Oelkers, Ryan J.; Paegert, Martin; Torres, Guillermo; Pepper, Joshua; De Lee, Nathan; Collins, Kevin; Latham, David W.; Muirhead, Philip S.; Chittidi, Jay; Rojas-Ayala, Bárbara; Fleming, Scott W.; Rose, Mark E.; Tenenbaum, Peter; Ting, Eric B. (2019-10-01), "The Revised TESS Input Catalog and Candidate Target List", *The Astronomical Journal*, **158** (4): 138, [arXiv](/source/ArXiv_(identifier)):[1905.10694](https://arxiv.org/abs/1905.10694), [Bibcode](/source/Bibcode_(identifier)):[2019AJ....158..138S](https://ui.adsabs.harvard.edu/abs/2019AJ....158..138S), [doi](/source/Doi_(identifier)):[10.3847/1538-3881/ab3467](https://doi.org/10.3847%2F1538-3881%2Fab3467), [ISSN](/source/ISSN_(identifier)) [0004-6256](https://search.worldcat.org/issn/0004-6256).

1. **[^](#cite_ref-SIMBADa_10-0)** ["ksi01 Lup"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=ksi01+Lup), *[SIMBAD](/source/SIMBAD)*, [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg), retrieved 2017-03-08.

1. **[^](#cite_ref-SIMBADb_11-0)** ["ksi02 Lup"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=ksi02+Lup), *[SIMBAD](/source/SIMBAD)*, [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg), retrieved 2017-03-08.

1. **[^](#cite_ref-Brown1997_13-0)** Brown, A. G. A.; Verschueren, W. (March 1997), "High S/N Echelle spectroscopy in young stellar groups. II. Rotational velocities of early-type stars in SCO OB2", *Astronomy and Astrophysics*, **319**: 811–838, [arXiv](/source/ArXiv_(identifier)):[astro-ph/9608089](https://arxiv.org/abs/astro-ph/9608089), [Bibcode](/source/Bibcode_(identifier)):[1997A&A...319..811B](https://ui.adsabs.harvard.edu/abs/1997A&A...319..811B).

1. **[^](#cite_ref-Tetzlaff2011_14-0)** Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", *Monthly Notices of the Royal Astronomical Society*, **410** (1): 190–200, [arXiv](/source/ArXiv_(identifier)):[1007.4883](https://arxiv.org/abs/1007.4883), [Bibcode](/source/Bibcode_(identifier)):[2011MNRAS.410..190T](https://ui.adsabs.harvard.edu/abs/2011MNRAS.410..190T), [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2010.17434.x](https://doi.org/10.1111%2Fj.1365-2966.2010.17434.x), [S2CID](/source/S2CID_(identifier)) [118629873](https://api.semanticscholar.org/CorpusID:118629873).

v t e Constellation of Lupus List of stars in Lupus Lupus in Chinese astronomy Stars Bayer α (Uridim) β γ δ ε ζ η θ ι κ λ μ ν1 ν2 ξ ο π ρ σ τ1 τ2 υ φ1 φ2 χ ψ1 ψ2 ω Flamsteed 1 (i) 2 (f) Variable RU EX GG GQ HR II IL IM KT (d) V407 V462 HR 5362 5364 5401 5651 (e) 5724 (k) 5825 (g) 5943 5967 HD 134004 135344 136164 141943 142527 143811 Other Gliese 588 HIP 70849 Lupus-TR-3 SSSPM J1549−3544 WASP-132 Exoplanets GQ Lupi b HIP 70849 b Lupus-TR-3b WASP-178b Star clusters NGC 5749 NGC 5822 NGC 5824 NGC 5927 NGC 5986 Nebulae IC 4406 NGC 5882 Galaxies IC 4444 NGC 5530 NGC 5643 Astronomical events SN 1006 Category

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