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Beta Aquilae

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Beta Aquilae
Location of β Aquilae (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Aquila[1]
Right ascension 19h 55m 18.793s[2]
Declination +06° 24′ 24.35″[2]
Apparent magnitude (V) 3.87 + 12.0[3]
Characteristics
Spectral type G9.5 IV[4] + M2.5 V[5]
U−B color index 0.48[6]
B−V color index 0.86[6]
R−I color index 0.49
Variable type Suspected
Astrometry
Radial velocity (Rv)−40.3±0.09[7] km/s
Proper motion (μ) RA: +45.944 mas/yr[2]
Dec.: −480.965 mas/yr[2]
Parallax (π)73.5249±0.1415 mas[8]
Distance44.36 ± 0.09 ly
(13.60 ± 0.03 pc)
Absolute magnitude (MV)+3.03[1]
Details
A
Mass1.24±0.02[9] M☉
Radius3.123±0.033[10] R☉
Luminosity6.18±0.26[10] L☉
Surface gravity (log g)3.66±0.03[10] cgs
Temperature5,163±17[10] K
Metallicity [Fe/H]−0.20±0.04[11] dex
Rotation5.08697±0.00031[12] days
Rotational velocity (v sin i)22.28[13] km/s
Age4.77±0.50[9] Gyr
Other designations
Alshain, Alschairn, β Aql, 60 Aquilae, BD+06°4357, FK5 749, GC 27587, GJ 771, HD 188512, HIP 98036, HR 7602, SAO 125235, PPM 168947, WDS 19553+0624, LHS 5350a, LTT 15822[14]
Database references
SIMBADdata
ARICNSdata

Beta Aquilae is a triple star[15] system in the equatorial constellation of Aquila. Its name is a Bayer designation that is Latinized from β Aquilae, and abbreviated Beta Aql or β Aql. This system is visible to the naked eye as a point-like source with an apparent visual magnitude of 3.87.[3] Based on parallax measurements, it is located at a distance of 44.4 light-years.[8] It is drifting closer to the Sun with a radial velocity of −40 km/s,[7] and is predicted to approach to within 27 light-years (8.4 pc) in roughly 207,000 years.[16]

Its two visible components are designated Beta Aquilae A and B. The former is formally named Alshain /ælˈʃeɪn/, the traditional name for the system.[17][18]

Nomenclature

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In this starfield showing many stars of Aquila constellation, the asterism α, β and γ Aquilae can be easily recognized on the left portion of the image.

β Aquilae (Latinised to Beta Aquilae) is the system's Bayer designation. The designations of the two components as Beta Aquilae A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[19]

The system bore the traditional name Alshain, derived from the Persian shāhīn-i tarazu "the scale beam", the Persian name for the asterism of α, β and γ Aquilae, itself a translation of the Arabic al-mizan "the balance". The name Tarazed for γ Aquilae is derived from the same Persian term.[17][18] In 2016, the IAU organized a Working Group on Star Names (WGSN)[20] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[21] It approved the name Alshain for the component Beta Aquilae A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.[18]

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Unuk al Ghyrab (عنق ألغراب - únuq al-ghuraab), which was translated into Latin as Collum Corvi, meaning the crow's neck.[22]

In Chinese, 河鼓 (Hé Gŭ), meaning River Drum, refers to an asterism consisting of Beta Aquilae, Altair and Gamma Aquilae.[23] Consequently, the Chinese name for Beta Aquilae itself is 河鼓一 (Hé Gŭ yī, English: the First Star of River Drum).[24]

Properties

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The primary, component A, is of magnitude 3.71 and spectral class G8IV. It has a very low level of surface magnetic activity and may be in a state similar to a Maunder minimum.[25] The activity shows a cycle of 969±27 d.[12] The star displays solar-like oscillations.[26] Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[27]

This is an aging subgiant star that has exhausted the supply of hydrogen at its core and is evolving into a giant.[12] Its angular diameter has been precisely determined using interferometry at the CHARA array, which combined with its estimated distance, result in a radius 3.123 times the radius of the Sun.[10] It has a mass 24% greater than the Sun's,[9] a luminosity 6.2 times that of the Sun, and an effective temperature of 5,163 K.[10]

The 12th magnitude secondary companion, designated component B, is a double-lined spectroscopic binary,[28] which is at an angular separation of 13 arcseconds from the primary. It has a stellar classification of M2.5 V,[5] matching a class M red dwarf.

In culture

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In the Chinese folk tale The Cowherd and the Weaver Girl, Beta and Gamma Aquilae are children of Niulang (牛郎, The Cowherd, Altair) and Zhinü (織女, The Princess, Vega).[29]

The Koori people of Victoria knew Beta and Gamma Aquilae as the black swan wives of Bunjil (Altair), the wedge-tailed eagle.[30]

USS Alshain (AKA-55) was a United States Navy ship.

References

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  1. 1 2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  2. 1 2 3 4 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 Eggleton, P. P.; Tokovinin, A. A. (2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  4. ↑ Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
  5. 1 2 Montes, D.; et al. (September 2018), "Calibrating the metallicity of M dwarfs in wide physical binaries with F-, G-, and K-primaries - I: High-resolution spectroscopy with HERMES: stellar parameters, abundances, and kinematics", Monthly Notices of the Royal Astronomical Society, 479 (1): 1332–1382, arXiv:1805.05394, Bibcode:2018MNRAS.479.1332M, doi:10.1093/mnras/sty1295.
  6. 1 2 Oja, T. (August 1986), "UBV photometry of stars whose positions are accurately known. III", Astronomy and Astrophysics Supplement Series, 65 (2): 405–4, Bibcode:1986A&AS...65..405O.
  7. 1 2 Jofré, E.; et al. (February 2015), "Stellar parameters and chemical abundances of 223 evolved stars with and without planets", Astronomy & Astrophysics, 574: 46, arXiv:1410.6422, Bibcode:2015A&A...574A..50J, doi:10.1051/0004-6361/201424474, S2CID 53666931, A50.
  8. 1 2 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.
  9. 1 2 3 Kjeldsen, Hans; et al. (2025). "Asteroseismology of the G8 subgiant β Aquilae with SONG-Tenerife, SONG-Australia and TESS". Astronomy & Astrophysics. 700: A39. arXiv:2506.00493. Bibcode:2025A&A...700A..39K. doi:10.1051/0004-6361/202554633.
  10. 1 2 3 4 5 6 Bustos, Romina V. Ibañez; Mourard, Denis; Nardetto, Nicolas; Jones, Jeremy; Ebrahimkutty, Nayeem; Jonák, Juraj; Nowacki, Hugo; Vrard, Mathieu; Berio, Philippe (2026-08-31), "Interferometric Survey of Stellar Parameters: Towards homogeneous FGK stars parameters and surface-brightness color relation in the context of PLATO space mission", arXiv:2608.30557 [astro-ph.SR].
  11. ↑ Karovicova, I.; et al. (February 2022), "Fundamental stellar parameters of benchmark stars from CHARA interferometry -- III. Giant and subgiant stars", Astronomy & Astrophysics, 658: A48, arXiv:2109.13258, Bibcode:2022A&A...658A..48K, doi:10.1051/0004-6361/202142100, ISSN 0004-6361
  12. 1 2 3 Butkovskaya, Varvara; et al. (February 2018), "Long-term stellar magnetic field study at the Crimean Astrophysical Observatory", Long-term Datasets for the Understanding of Solar and Stellar Magnetic Cycles, Proceedings of the International Astronomical Union, IAU Symposium, vol. 340, pp. 35–38, Bibcode:2018IAUS..340...35B, doi:10.1017/S1743921318001035, S2CID 125610540.
  13. ↑ Rains, Adam D.; et al. (April 2020), "Precision angular diameters for 16 southern stars with VLTI/PIONIER", Monthly Notices of the Royal Astronomical Society, 493 (2): 2377–2394, arXiv:2004.02343, Bibcode:2020MNRAS.493.2377R, doi:10.1093/mnras/staa282, S2CID 214802418
  14. ↑ "bet Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2025-04-13.
  15. ↑ Fuhrmann, K.; et al. (February 2017), "Multiplicity among Solar-type Stars", The Astrophysical Journal, 836 (1): 23, Bibcode:2017ApJ...836..139F, doi:10.3847/1538-4357/836/1/139, 139.
  16. ↑ Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind", Astronomy & Astrophysics, 575: 13, arXiv:1412.3648, Bibcode:2015A&A...575A..35B, doi:10.1051/0004-6361/201425221, S2CID 59039482, A35.
  17. 1 2 Kunitzsch, Paul; Smart, Tim (2006), A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.), Cambridge, Massachusetts: Sky Pub, ISBN 978-1-931559-44-7.
  18. 1 2 3 "IAU Catalog of Star Names". Retrieved 16 August 2026.
  19. ↑ Hessman, F. V.; et al. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  20. ↑ IAU Working Group on Star Names (WGSN), International Astronomical Union, archived from the original on 10 June 2016, retrieved 22 May 2016.
  21. ↑ WG Triennial Report (2015-2018) - Star Names (PDF), p. 5, archived from the original (PDF) on 2019-08-23, retrieved 2018-07-14.
  22. ↑ Knobel, E. B. (June 1895), "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket", Monthly Notices of the Royal Astronomical Society, 55: 429–438, Bibcode:1895MNRAS..55..429K, doi:10.1093/mnras/55.8.429.
  23. ↑ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  24. ↑ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 26, 2008.
  25. ↑ Andretta, V.; et al. (February 2005), "The Ca II Infrared Triplet as a stellar activity diagnostic . I. Non-LTE photospheric profiles and definition of the RIRT indicator", Astronomy and Astrophysics, 430 (2): 669–677, Bibcode:2005A&A...430..669A, doi:10.1051/0004-6361:20041745.
  26. ↑ Corsaro, E.; et al. (January 2012), "Solar-like oscillations in the G9.5 subgiant β Aquilae", Astronomy & Astrophysics, 537, id. A9, arXiv:1110.2772, Bibcode:2012A&A...537A...9C, doi:10.1051/0004-6361/201117158.
  27. ↑ Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society, 25: 1319, Bibcode:1993AAS...183.1710G, archived from the original on 2019-06-25, retrieved 2012-02-04
  28. ↑ Bonfils, Xavier; et al. (2005), "Metallicity of M dwarfs. I. A photometric calibration and the impact on the mass-luminosity relation at the bottom of the main sequence", Astronomy and Astrophysics, 442 (2): 635–642, arXiv:astro-ph/0503260, Bibcode:2005A&A...442..635B, doi:10.1051/0004-6361:20053046, S2CID 13900901.
  29. ↑ Ridpath, Ian. "Star Tales – Aquila". Retrieved 18 August 2026.
  30. ↑ Mudrooroo (1994), Aboriginal mythology : an A-Z spanning the history of aboriginal mythology from the earliest legends to the present day, London: HarperCollins, p. 4, ISBN 1-85538-306-3.
  31. Soubiran, C.; et al. (February 1, 2024), "Gaia FGK benchmark stars: Fundamental Teff and log g of the third version", Astronomy and Astrophysics, 682: A145, arXiv:2310.11302, Bibcode:2024A&A...682A.145S, doi:10.1051/0004-6361/202347136, ISSN 0004-6361
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