Gamma Aquarii
Star in the constellation Aquarius
From Wikipedia, the free encyclopedia
Gamma Aquarii, or γ Aquarii, is a binary star system[6] in the constellation of Aquarius. It has an apparent visual magnitude of 3.849,[2] making it one of the brighter members of the constellation. Based upon parallax measurements, this star is located at a distance of 164 light-years (50 parsecs).[1] It is drifting closer to Earth with a radial velocity of −16 km/s.[4] It is a candidate member of the Hyades Supercluster.[5]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 21m 39.37542s[1] |
| Declination | −01° 23′ 14.4031″[1] |
| Apparent magnitude (V) | 3.849[2] |
| Characteristics | |
| Spectral type | A0 V[3] |
| U−B color index | −0.092[2] |
| B−V color index | −0.060[2] |
| Astrometry | |
| Radial velocity (Rv) | −15.7±0.9[4] km/s |
| Proper motion (μ) | RA: +129.53 mas/yr[1] Dec.: +7.77 mas/yr[1] |
| Parallax (π) | 19.92±1.04 mas[1] |
| Distance | 164 ± 9 ly (50 ± 3 pc) |
| Absolute magnitude (MV) | +0.10[5] |
| Details | |
| Aa | |
| Mass | 2.72±0.04[6] M☉ |
| Radius | 2.7[6] R☉ |
| Surface gravity (log g) | 3.99±0.14[7] cgs |
| Temperature | 10,637±362[7] K |
| Metallicity [Fe/H] | +0.30[8] dex |
| Rotational velocity (v sin i) | 80[9] km/s |
| Age | 280±20[6] Myr |
| Ab | |
| Mass | 0.56[6] M☉ |
| Radius | 0.5[6] R☉ |
| Temperature | 3,900[6] K |
| Other designations | |
| Sadalachbia, Sadachbia, Gamma Aqr, γ Aqr, 48 Aquarii, BD−02°5741, FK5 842, HD 212061, HIP 110395, HR 8518, SAO 146044, ADS 15864, WDS J22217-0123A[10] | |
| Database references | |
| SIMBAD | data |
The two components are designated Gamma Aquarii Aa, formally called Sadachbia /səˈdækbiə/,[11] and Ab.
Nomenclature
γ Aquarii, Latinised to Gamma Aquarii, is the system's Bayer designation. WDS J22217-0123 A is its designation in the Washington Double Star Catalog.
It bore the traditional name Sadachbia, from an Arabic expression سعد الأخبية (sa‘d al-’axbiyah), meaning "luck of the homes (tents)". In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Aoul al Achbiya (أول ألأجبية - awwil al ahbiyah), which was translated into Latin as Prima Tabernaculorum, meaning the first of luck of the homes (tents).[12] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalogue and standardize proper names for stars. The WGSN approved the name Sadachbia for the component WDS J22217-0123 Aa on 21 August 2016, and it is now so included in the List of IAU-approved Star Names.[11]
This star, along with Pi Aquarii, Zeta Aquarii and Eta Aquarii, were al Aḣbiyah الأخبية "the Tent".[14][15][16]
In Hindi it has been called Satabhishaj or Shatabhisha (a hundred physicians), but this name originally referred to λ Aquarii and its association with this star is likely an error.[17] Equivalent names are Sadhayam in Tamil and Chathayam (written as ചതയം) in Malayalam.[citation needed]
In Chinese, 墳墓 (Fén Mù), meaning Tomb, refers to an asterism consisting of Gamma Aquarii, Zeta Aquarii, Eta Aquarii and Pi Aquarii.[18] Consequently, the Chinese name for Gamma Aquarii itself is 墳墓二 (Fén Mù èr, English: the Second Star of Tomb).[19]
Properties
In 1978 through 1984, H. A. McAlister listed this as a spectroscopic binary star system that is unresolved by speckle interferometry,[20][21] and it is listed as such in the 1991 revision of the Bright Star Catalogue.[22] In 2008, P. P. Eggleton and A. A. Tokovinin listed it as a single star in their catalogue of multiplicity.[23] However, in 2024, a companion star to Gamma Aquarii was detected by interferometric observations.[6]
The primary is an A-type main sequence star with a stellar classification of A0 V,[3] around 2.7 times larger and more massive than the Sun.[6] It was a candidate Lambda Boötis star, suggesting it may have accreted low-metallicity circumstellar gas some time in the past.[24] But it has since been excluded.[25] The star is spinning relatively rapidly with a projected rotational velocity of 80 km s−1.[9] This value gives a lower bound on the actual azimuthal velocity along the star's equator. The outer atmosphere of Gamma Aquarii is radiating energy at an effective temperature of 10,500 K,[8] which is nearly double the temperature at the surface of the Sun. This heat is what gives Gamma Aquarii the white-hot glow of an A-type star.[26]
The secondary component is a low-mass star which has around 0.56 times the mass and half the radius of the Sun. Its effective temperature of 3,900 K[6] gives it the orange hue typical of late K-type stars.[26] This secondary could explain the X-ray emission detected from this system with the ROSAT X-ray telescope.[6] Located 1.9 astronomical units from each other, both stars take around a year to orbit the system's center of mass.[6]