# Iota1 Librae

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Multiple star system in the constellation Libra

For other stars with this Bayer designation, see [ι Librae](/source/Iota_Librae).

Iota1 Librae Location of ι1 Librae (circled in red) Observation data Epoch J2000 Equinox J2000 Constellation Libra Right ascension 15h 12m 13.29025s[1] Declination −19° 47′ 30.1592″[1] Apparent magnitude (V) +4.54[2] (5.1 + 5.6 + 10.4 + 10.9)[3] Characteristics Spectral type B9IVpSi + B9[4] + G5IV[3] U−B color index −0.38[2] B−V color index −0.08[2] Variable type Alpha2 Canum Venaticorum Astrometry Radial velocity (Rv) −11.6[2] km/s Proper motion (μ) RA: −35.40[1] mas/yr Dec.: −32.79[1] mas/yr Parallax (π) 8.59±0.25 mas[1] Distance 380 ± 10 ly (116 ± 3 pc) Absolute magnitude (MV) −0.79[5] Position (relative to A)[3] Component BC Angular distance 57.8″ Position angle 111° Orbit[6] Primary Aa Name Ab Period (P) 23.512±0.026 yr Semi-major axis (a) 0.12932±0.00064″ Eccentricity (e) 0.2440±0.0029 Inclination (i) 154.2±1.0° Longitude of the node (Ω) 173.8±2.3° Periastron epoch (T) 1971.034±0.076 Argument of periastron (ω) (secondary) 340.1±2.8° Semi-amplitude (K1) (primary) 3.4[7] km/s Position (relative to B)[3] Component C Angular distance 2.058″ Position angle 111° Details[3] Aa Mass 3.61 M☉ Ab Mass 3.12 M☉ B Mass 0.98 M☉ C Mass 0.91 M☉ Other designations ι1 Lib, 24 Librae, BD−19°4047, HD 134759, HIP 74392, HR 5652, SAO 159090, WDS J15122-1948A[2] Database references SIMBAD data

**Iota1 Librae** is a quadruple[4] [star system](/source/Star_system) in the [constellation](/source/Constellation) [Libra](/source/Libra_(constellation)). Its name is a [Bayer designation](/source/Bayer_designation) that is [Latinized](/source/Romanization_of_Greek) from **ι1 Librae**, and abbreviated Iota1 Lib or ι1 Lib. Its [apparent magnitude](/source/Apparent_magnitude) is 4.54. It is located 379 [light years](/source/Light_years) from earth.[8]

## Visibility

Due to its southern location, although the star can be seen from most regions of the earth, observers in the southern hemisphere are more advantaged. Near [Antarctica](/source/Antarctica), it appears [circumpolar](/source/Circumpolar_star), while it always remains invisible only in the vicinity of the [Arctic Circle](/source/Arctic_Circle). Its magnitude of 4.5 means that [naked eye](/source/Naked_eye) visibility is dependent on a sky sufficiently free from the effects of [light pollution](/source/Light_pollution).

The best time for observation in the evening sky falls in the months between May and September; from both hemispheres of the period of visibility remains approximately the same, thanks to the position of the star not far from the celestial equator.

## Physical

A [light curve](/source/Light_curve) for Iota1 Librae plotted from *[STEREO](/source/STEREO)* data, adapted from Wraight *et al.* (2012)[9]

Iota1 Librae is a quadruple star system.[4] The inner pair, designated components Aa and Ab, form a [spectroscopic binary](/source/Spectroscopic_binary)[7] with an [orbital period](/source/Orbital_period) of 23.512 years and an [eccentricity](/source/Orbital_eccentricity) of 0.2440.[6] The brighter member has a [stellar classification](/source/Stellar_classification) of B9 IVp Si,[4] indicating it is a [B-type](/source/B-type_star) [subgiant star](/source/Subgiant_star) with an overabundance of [silicon](/source/Silicon) in the [photosphere](/source/Photosphere). It is a [variable star](/source/Variable_star) of the [Alpha2 Canum Venaticorum](/source/Alpha2_Canum_Venaticorum_variable) type with a magnitude that varies from 4.53 to 4.56, while its spectrum likewise shows variability.[10] The secondary component is of class B9.[4] The two stars are very close together (0.129 [arcsec](/source/Arcsecond) away), respectively of magnitude 5.10 and 5.60.[3]

The two other stars are the components C and D; separated by 57.8" from AB and 2.058" from each other. The combined spectrum is G5IV, and each star has masses of 0.98 and 0.91 solar masses, and magnitudes 10.40 and 10.90, respectively.[3]

Due to its position on the ecliptic, it is sometimes obscured by the Moon or planets. A lunar occultation took place April 4, 2012.[11]

## References

1. ^ [***a***](#cite_ref-vanLeeuwen2007_1-0) [***b***](#cite_ref-vanLeeuwen2007_1-1) [***c***](#cite_ref-vanLeeuwen2007_1-2) [***d***](#cite_ref-vanLeeuwen2007_1-3) [***e***](#cite_ref-vanLeeuwen2007_1-4) van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", *Astronomy and Astrophysics*, **474** (2): 653–664, [arXiv](/source/ArXiv_(identifier)):[0708.1752](https://arxiv.org/abs/0708.1752), [Bibcode](/source/Bibcode_(identifier)):[2007A&A...474..653V](https://ui.adsabs.harvard.edu/abs/2007A&A...474..653V), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078357](https://doi.org/10.1051%2F0004-6361%3A20078357), [S2CID](/source/S2CID_(identifier)) [18759600](https://api.semanticscholar.org/CorpusID:18759600).

1. ^ [***a***](#cite_ref-SIMBAD_2-0) [***b***](#cite_ref-SIMBAD_2-1) [***c***](#cite_ref-SIMBAD_2-2) [***d***](#cite_ref-SIMBAD_2-3) [***e***](#cite_ref-SIMBAD_2-4) ["iot01 Lib"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=iot01+Lib). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2017-12-16.

1. ^ [***a***](#cite_ref-Tokovinin2018_3-0) [***b***](#cite_ref-Tokovinin2018_3-1) [***c***](#cite_ref-Tokovinin2018_3-2) [***d***](#cite_ref-Tokovinin2018_3-3) [***e***](#cite_ref-Tokovinin2018_3-4) [***f***](#cite_ref-Tokovinin2018_3-5) [***g***](#cite_ref-Tokovinin2018_3-6) Tokovinin, Andrei (2018-03-01), "The Updated Multiple Star Catalog", *The Astrophysical Journal Supplement Series*, **235** (1): 6, [arXiv](/source/ArXiv_(identifier)):[1712.04750](https://arxiv.org/abs/1712.04750), [Bibcode](/source/Bibcode_(identifier)):[2018ApJS..235....6T](https://ui.adsabs.harvard.edu/abs/2018ApJS..235....6T), [doi](/source/Doi_(identifier)):[10.3847/1538-4365/aaa1a5](https://doi.org/10.3847%2F1538-4365%2Faaa1a5), [ISSN](/source/ISSN_(identifier)) [0067-0049](https://search.worldcat.org/issn/0067-0049). [Iota1 Librae's database entry](https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/ApJS/235/6&ID=15122-1948) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Eggleton2008_4-0) [***b***](#cite_ref-Eggleton2008_4-1) [***c***](#cite_ref-Eggleton2008_4-2) [***d***](#cite_ref-Eggleton2008_4-3) [***e***](#cite_ref-Eggleton2008_4-4) Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", *[Monthly Notices of the Royal Astronomical Society](/source/Monthly_Notices_of_the_Royal_Astronomical_Society)*, **389** (2): 869–879, [arXiv](/source/ArXiv_(identifier)):[0806.2878](https://arxiv.org/abs/0806.2878), [Bibcode](/source/Bibcode_(identifier)):[2008MNRAS.389..869E](https://ui.adsabs.harvard.edu/abs/2008MNRAS.389..869E), [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2008.13596.x](https://doi.org/10.1111%2Fj.1365-2966.2008.13596.x), [S2CID](/source/S2CID_(identifier)) [14878976](https://api.semanticscholar.org/CorpusID:14878976).

1. **[^](#cite_ref-Anderson2012_5-0)** Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", *Astronomy Letters*, **38** (5): 331, [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971), [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A), [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015), [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644).

1. ^ [***a***](#cite_ref-Mason2023_6-0) [***b***](#cite_ref-Mason2023_6-1) Mason, Brian D.; Tokovinin, Andrei; Mendez, Rene A.; Costa, Edgardo (October 2023), "Speckle Interferometry at SOAR in 2022", *The Astronomical Journal*, **166** (4): 139, [Bibcode](/source/Bibcode_(identifier)):[2023AJ....166..139M](https://ui.adsabs.harvard.edu/abs/2023AJ....166..139M), [doi](/source/Doi_(identifier)):[10.3847/1538-3881/acedaf](https://doi.org/10.3847%2F1538-3881%2Facedaf), [ISSN](/source/ISSN_(identifier)) [0004-6256](https://search.worldcat.org/issn/0004-6256).

1. ^ [***a***](#cite_ref-Pourbaix2004_7-0) [***b***](#cite_ref-Pourbaix2004_7-1) Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", *Astronomy & Astrophysics*, **424**: 727–732, [arXiv](/source/ArXiv_(identifier)):[astro-ph/0406573](https://arxiv.org/abs/astro-ph/0406573), [Bibcode](/source/Bibcode_(identifier)):[2004A&A...424..727P](https://ui.adsabs.harvard.edu/abs/2004A&A...424..727P), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20041213](https://doi.org/10.1051%2F0004-6361%3A20041213), [S2CID](/source/S2CID_(identifier)) [119387088](https://api.semanticscholar.org/CorpusID:119387088).

1. **[^](#cite_ref-Vizier_8-0)** [Extended Hipparcos Compilation (XHIP) (+ Anderson, 2012)](http://vizier.u-strasbg.fr/viz-bin/VizieR-5?-ref=VIZ50573aac4cd&-out.add=.&-source=V/137C/XHIP&recno=74147)

1. **[^](#cite_ref-Wraight_9-0)** Wraight, K. T.; Fossati, L.; Netopil, M.; Paunzen, E.; Rode-Paunzen, M.; Bewsher, D.; Norton, A. J.; White, Glenn J. (February 2012), "A photometric study of chemically peculiar stars with the STEREO satellites – I. Magnetic chemically peculiar stars", *Monthly Notices of the Royal Astronomical Society*, **420** (1): 757–772, [arXiv](/source/ArXiv_(identifier)):[1110.6283](https://arxiv.org/abs/1110.6283), [Bibcode](/source/Bibcode_(identifier)):[2012MNRAS.420..757W](https://ui.adsabs.harvard.edu/abs/2012MNRAS.420..757W), [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2011.20090.x](https://doi.org/10.1111%2Fj.1365-2966.2011.20090.x)

1. **[^](#cite_ref-Vizier2_10-0)** [General Catalogue of Variable Stars (Samus + 2007-2012)](http://vizier.u-strasbg.fr/viz-bin/VizieR-5?-ref=VIZ50573aac4cd&-out.add=.&-source=B/gcvs/nsv_cat&recno=6981)

1. **[^](#cite_ref-OATO_11-0)** ["Moon occults ι Librae (2012-04-09 02:03 CEST)"](http://www.oato.inaf.it/index.php?option=com_events&task=view_detail&agid=2141&year=2012&month=04&day=09&Itemid=340&catids=87). [Turin Astronomical Observatory](/source/Turin_Astronomical_Observatory). Retrieved March 23, 2012.{{[cite web](https://en.wikipedia.org/wiki/Template:Cite_web)}}: CS1 maint: deprecated archival service ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_deprecated_archival_service))

## External links

- [Simbad archive](http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Iota+Librae&submit=display+all+measurements)

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 [Iota1 Librae](https://en.wikipedia.org/wiki/Iota1_Librae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Iota1_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.