Epoch J2000 Equinox J2000
|Right ascension||19h 55m 18.8s|
|Declination||+06° 24′ 24″|
|Apparent magnitude (V)||3.71/11.4|
|Spectral type||G8 IVvar|
|U−B color index||0.48|
|B−V color index||0.86|
|R−I color index||0.49|
|Radial velocity (Rv)||-40.3 km/s|
|Proper motion (μ)||RA: 46.35 mas/yr
Dec.: -481.32 mas/yr
|Parallax (π)||72.95 ± 0.83 mas|
|Distance||44.7 ± 0.5 ly
(13.7 ± 0.2 pc)
|Mass||1.26 ± 0.18 M☉|
|Radius||3.28 ± 0.15 R☉|
|Luminosity||6.0 ± 0.3 L☉|
|Surface gravity (log g)||3.60 cgs|
|Metallicity [Fe/H]||–0.30 dex|
|Rotational velocity (v sin i)||0.9 km/s|
It has magnitude 3.71 and is of 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. It is approximately 44.7 light years from Earth. It has a 12th magnitude optical companion, Beta Aquilae B, which is 13 arcseconds away in the sky.
It bore the traditional name Alshain derived from the Perso-Arabic term الشاهين aš-šāhīn "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 International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Alshain for this star on 21 August 2016 and it is now so entered in the IAU Catalog of 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, Beta Aquilae itself is known as 河鼓一 (Hé Gŭ yī, English: the First Star of River Drum.)
USS Alshain (AKA-55) was a United States navy ship.
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