Zeta Aquarii
Zeta Aquarii (ζ Aquarii, ζ Aqr) is the Bayer designation for a triple star system,[7] the central star of the "water jar" asterism[9] in the equatorial constellation of Aquarius. The combined apparent visual magnitude of this system is 3.65,[2] which is readily visible to the naked eye. Parallax measurements yield a distance estimate of around 92 light-years (28 parsecs) from Earth.[1]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 28m 49.90685s[1] |
| Declination | –00° 01′ 11.7942″[1] |
| Apparent magnitude (V) | 3.65[2] (4.42 / 4.51)[3] |
| Characteristics | |
| Spectral type | F3 V + F6 IV[3] |
| U−B color index | –0.01[2] |
| B−V color index | +0.40[2] |
| Astrometry | |
| Radial velocity (Rv) | +24.9/+28.9[4] km/s |
| Proper motion (μ) | RA: +182.92[1] mas/yr Dec.: +50.36[1] mas/yr |
| Parallax (π) | 35.50 ± 1.26[1] mas |
| Distance | 92 ± 3 ly (28.2 ± 1.0 pc) |
| Absolute magnitude (MV) | 1.15[5] |
| Orbit[6] | |
| Primary | ζ Aqr Aa |
| Companion | ζ Aqr Ab |
| Period (P) | 25.95 ± 0.048 yr |
| Semi-major axis (a) | 0.385″ |
| Eccentricity (e) | 0.872 ± 0.006 |
| Inclination (i) | 11.8 ± 6.7° |
| Longitude of the node (Ω) | 293.7 ± 74° |
| Periastron epoch (T) | B 2006.52 ± 0.13 |
| Argument of periastron (ω) (secondary) | 100.9 ± 73° |
| Orbit[7] | |
| Primary | ζ Aqr A |
| Companion | ζ Aqr B |
| Period (P) | 540 ± 15 yr |
| Semi-major axis (a) | 3.496 ± 0.046″ |
| Eccentricity (e) | 0.419 ± 0.011 |
| Inclination (i) | 142.0 ± 0.4° |
| Longitude of the node (Ω) | 131.3 ± 0.8° |
| Periastron epoch (T) | B 1981.50 ± 0.58 |
| Argument of periastron (ω) (secondary) | 269.3 ± 1.7° |
| Details | |
| ζ Aqr A | |
| Mass | 1.4 / 0.6[7] M☉ |
| Metallicity [Fe/H] | –0.13[5] dex |
| Rotational velocity (v sin i) | 62[8] km/s |
| Age | 1.0[5] Gyr |
| ζ Aqr B | |
| Mass | 1.4[7] M☉ |
| Rotational velocity (v sin i) | 56[8] km/s |
| Other designations | |
| 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. | |
| Database references | |
| SIMBAD | ζ Aqr |
| ζ Aqr A | |
| ζ Aqr B | |
Etymology
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Achr al Achbiya (آخر ألأخبية - ākhir al-akhbiya), which was translated into Latin as Postrema Tabernaculorum, meaning the end of luck of the homes (tents).[10] This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and η Aqr (Hydria), were al-Akḣbiya (الأخبية), the Tents.[11][12]
In Chinese, 墳墓 (Fén Mù), meaning Tomb, refers to an asterism consisting of ζ Aquarii, γ Aquarii, η Aquarii and π Aquarii.[13] Consequently, the Chinese name for ζ Aquarii itself is 墳墓一 (Fén Mù yī, English: the First Star of Tomb.)[14]
Properties
The binary was measured by William Herschel in 1779 however Christian Mayer, listed an earlier observation in his first double-star catalog in 1784 so its true discoverer is not clear.[7] 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.[15]
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.[3] The fact that their brightness is so similar makes the pair easy to measure and resolve.
Zeta Aquarii A is known to be an astrometric binary system, as it undergoes regular perturbations from its orbit. It has a 26-year orbital period and a semimajor axis of 0.11″. The secondary's mass is 0.6 M☉.[7]
Zeta Aquarii is currently a northern hemisphere object. In 2004 it was directly above the celestial equator, and before that it was located south of it.
References
- van Leeuwen, F. (November 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.
- 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:1010.4176, Bibcode:2010PASP..122.1483T, doi:10.1086/657903.
- Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Washington, 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 (3): 989–1019, arXiv:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959.
- "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 14 June 2017.
- Tokovinin, Andrei (2016). "The Triple System Zeta Aquarii". The Astrophysical Journal. 831 (2): 151. arXiv:1608.08564. Bibcode:2016ApJ...831..151T. doi:10.3847/0004-637X/831/2/151.
- Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 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 (8): 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 978-0-486-21079-7, retrieved 2010-12-12.
- (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) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 16 日
- Olevic, D.; Cvetkovic, Z. (2004), "Orbits of 6 Binaries", Serbian Astronomical Journal, 168 (168): 25, Bibcode:2004SerAJ.168...25O, doi:10.2298/saj0468025o.
External links
- 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
