Epoch J2000 Equinox J2000
|Right ascension||22h 28m 49.90685s|
|Declination||–00° 01′ 11.7942″|
|Apparent magnitude (V)||3.65 (4.42/4.51)|
|Spectral type||F3 V + F6 IV|
|U−B color index||–0.01|
|B−V color index||+0.40|
|Radial velocity (Rv)||+24.9/+28.9 km/s|
|Proper motion (μ)||RA: +182.92 mas/yr
Dec.: +50.36 mas/yr
|Parallax (π)||35.50 ± 1.26 mas|
|Distance||92 ± 3 ly
(28.2 ± 1.0 pc)
|Absolute magnitude (MV)||1.15|
|ζ Aqr A|
|Metallicity [Fe/H]||–0.13 dex|
|Rotational velocity (v sin i)||62 km/s|
|ζ Aqr B|
|Rotational velocity (v sin i)||56 km/s|
|Companion||ζ Aquarii B|
|Period (P)||587.18 ± 1.09 yr|
|Semi-major axis (a)||3.847 ± 0.147"|
|Eccentricity (e)||0.40 ± 0.01|
|Inclination (i)||138.2 ± 0.2°|
|Longitude of the node (Ω)||129.8 ± 0.3°|
|Periastron epoch (T)||1957.6|
|ζ Aqr A: ζ2 Aquarii, Zeta2 Aquarii, HD 213052, HR 8559, SAO 146108.|
|ζ Aqr B: ζ1 Aquarii, Zeta1 Aquarii, HD 213051, HR 8558, SAO 146107.|
Zeta Aquarii (ζ Aquarii, ζ Aqr) is the Bayer designation for a binary, or possibly a triple star system; the central star of the "water jar" asterism in the equatorial constellation of Aquarius. The combined apparent visual magnitude of this system is 3.65, which is readily visible to the naked eye. Parallax measurements yield a distance estimate of around 92 light-years (28 parsecs) from Earth.
Zeta Aquarii has the traditional name Sadaltager (or Altager), from the Arabic سعد التاجر (sa‘d al-tājir), meaning "luck of the merchant". In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Achr al Achbiya (أجر ألأجبية - akhir al ahbiyah), which was translated into Latin as Postrema Tabernaculorum, meaning the end of luck of the homes (tents). This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and η Aqr (Hydria), were al Aḣbiyah (الأخبية), the Tent.
In Chinese, 墳墓 (Fén Mù), meaning Tomb, refers to an asterism consisting of ζ Aquarii, γ Aquarii, η Aquarii and π Aquarii. Consequently, ζ Aquarii itself is known as 墳墓一 (Fén Mù yī, English: the First Star of Tomb.)
Christian Mayer, director of the Mannheim Observatory, is considered the first to have observed Zeta Aquarii to be double, in 1777. A couple of years later, William Herschel also discovered this duality. The two stars have an orbital period of about 587 years. The semimajor axis is 3.8 arcseconds and they have an orbital eccentricity of 0.40. The orbital plane is inclined by 138.2° to the line of sight.
The brighter component, ζ Aquarii A (also called ζ2 Aquarii), is a yellow-white-hued F-type main sequence star with an apparent magnitude of +4.42. Its companion, ζ Aquarii B (also called ζ1 Aquarii), is a yellow-white-hued F-type subgiant with an apparent magnitude of +4.51. The fact that their brightness is so similar makes the pair easy to measure and resolve.
ζ Aquarii B is a suspected astrometric binary system with a 25.8 year orbital period and a semimajor axis of 10.8 astronomical units. If this is confirmed, then the smaller companion may be a red dwarf with a classification of M0 V and 40% of the Sun's mass.
- van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: , Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
- Nicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Astronomy and Astrophysics Supplement Series. 34: 1–49. Bibcode:1978A&AS...34....1N.
- Tokovinin, A.; et al. (December 2010), "High-Resolution Imaging at the SOAR Telescope", Publications of the Astronomical Society of the Pacific, 122 (898): 1483–1494, arXiv: , Bibcode:2010PASP..122.1483T, doi:10.1086/657903.
- Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
- Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics, 418: 989–1019, arXiv: , Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959.
- Olevic, D.; Cvetkovic, Z. (2004), "Orbits of 6 Binaries", Serbian Astronomical Journal, 168: 25, Bibcode:2004SerAJ.168...25O, doi:10.2298/saj0468025o.
- Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1), Bibcode:1970CoAsi.239....1B.
- Dibon-Smith, Richard, "z Aquarii", The Constellations Web Page, retrieved 2012-07-10.
- 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, Bibcode:1895MNRAS..55..429K, doi:10.1093/mnras/55.8.429.
- Davis Jr., G. A. (October 1944), "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names", Popular Astronomy, 52 (3): 12, Bibcode:1944PA.....52....8D.
- Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 52, ISBN 0-486-21079-0, retrieved 2010-12-12.
- γ Aqr as Aoul al Achbiya or Prima Tabernaculorum (the first of luck of the homes or tents), π Aqr as Wasat al Achbiya or Media Tabernaculorum (the middle of luck of the homes or tents) and ζ Aqr as Achr al Achbiya or Postrema Tabernaculorum (the end of luck of the homes or tents). η Aqr should be designated as al Achbiya consistently, but it was not designated as the Arabian name except the name Hydria (Greek) or Deli (Hebrew)
- (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.
- (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 16 日
- Double Stars to Follow, Part IV: Zeta Aquarii and Mu Cygni. by Martin Gaskell, Prairie Astronomy Club Home Page.
- "This Month's Double Stars" by Richard Jaworski.
- Image ζ Aquarii