Epoch J2000 Equinox J2000
|Right ascension||19h 55m 18.79256s|
|Declination||+06° 24′ 24.3425″|
|Apparent magnitude (V)||3.87 + 12.0|
|Spectral type||G9.5 IV|
|U−B color index||0.48|
|B−V color index||0.86|
|R−I color index||0.49|
|Radial velocity (Rv)||−40.3±0.09 km/s|
|Proper motion (μ)|| RA: 45.27 mas/yr |
Dec.: −481.91 mas/yr
|Parallax (π)||73.00 ± 0.20 mas|
|Distance||44.7 ± 0.1 ly |
(13.70 ± 0.04 pc)
|Absolute magnitude (MV)||+3.03|
|Surface gravity (log g)||3.54±0.14 cgs|
|Metallicity [Fe/H]||−0.19±0.05 dex|
|Rotational velocity (v sin i)||22.28 km/s|
Beta Aquilae, Latinized from β Aquilae, is a binary star system in the equatorial constellation of Aquila. It is visible to the naked eye as a point-like source with an apparent visual magnitude of 3.87. Based on parallax measurements obtained during the Hipparcos mission, it is located at a distance of approximately 44.7 light-years from the Sun. It is drifting closer to the Sun with a radial velocity of −40 km/s.
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).
The system bore the traditional name Alshain derived from the Perso-Arabic term الشاهين, aš-šāhīn, meaning "the (peregrine) falcon", perhaps by folk etymology from the Persian šāhīn tarāzū (or possibly šāhīn tara zed; see Gamma Aquilae), the Persian name for the asterism α, β and γ Aquilae. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. 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.
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.
In Chinese, 河鼓 (Hé Gŭ), meaning River Drum, refers to an asterism consisting of Beta Aquilae, Altair and Gamma Aquilae. Consequently, the Chinese name for Beta Aquilae itself is 河鼓一 (Hé Gŭ yī, English: the First Star of River Drum).
USS Alshain (AKA-55) was a United States navy ship.
The primary (Beta Aquilae 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. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. A subgiant with a mass 26% greater than the Sun's, a luminosity six times that of the Sun, and a radius about thrice solar.
The secondary (Beta Aquilae B) is a 12th magnitude companion which is 13 arcseconds away in the sky. It is a class M red dwarf with a mass a third that of the Sun and a luminosity 2.5% the Sun's.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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
- Bruntt, H.; et al. (July 2010), "Accurate fundamental parameters for 23 bright solar-type stars", Monthly Notices of the Royal Astronomical Society, 405 (3): 1907–1923, arXiv:1002.4268, Bibcode:2010MNRAS.405.1907B, doi:10.1111/j.1365-2966.2010.16575.x, S2CID 118495267
- Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal, 687 (2): 1264–1293, arXiv:0807.1686, Bibcode:2008ApJ...687.1264M, doi:10.1086/591785, S2CID 27151456
- 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.
- "Naming Stars". IAU.org. Retrieved 3 March 2018.
- Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
- IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
- "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
- 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.
- (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.
- (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.
- 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.
- 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, retrieved 2012-02-04
- 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.