Zeta Aquarii

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Zeta Aquarii A/B
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings
Cercle rouge 100%.svg

Location of ζ Aquarii (circled)
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]
Details
ζ Aqr A
Mass 1.72[6] M
Metallicity [Fe/H] –0.13[5] dex
Rotational velocity (v sin i) 62[7] km/s
Age 1.0[5] Gyr
ζ Aqr B
Mass 1.65[6] M
Rotational velocity (v sin i) 56[7] km/s
Orbit[6]
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
Other designations
55 Aquarii, ADS 15971, BD−00°4365, HIP 110960.
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 data
Database references
SIMBAD data

Zeta Aquarii (ζ Aquarii, ζ Aqr) is the Bayer designation for a binary, or possibly a triple star system;[3] the central star of the "water jar" asterism[8] 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]

Etymology[edit]

Zeta Aquarii has the traditional name Sadaltager (or Altager), from the Arabic سعد التاجر sa‘d al-tājir "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).[9] This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and η Aqr (Hydria), were al Aḣbiyah (الأخبية), the Tent.[10][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, ζ Aquarii itself is known as 墳墓一 (Fén Mù yī, English: the First Star of Tomb.)[14]

Properties[edit]

Christian Mayer, director of the Mannheim Observatory, is considered the first to have observed Zeta Aquarii to be double, in 1777.[citation needed] A couple of years later, William Herschel also discovered this duality.[citation needed] 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.[6]

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.

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.[3]

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.[citation needed]

References[edit]

  1. ^ a b c d e f 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. 
  2. ^ a b c d 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. 
  3. ^ a b c d e 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. 
  4. ^ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953QB901.W495...... 
  5. ^ a b c 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:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959. 
  6. ^ a b c d Olevic, D.; Cvetkovic, Z. (2004), "Orbits of 6 Binaries", Serbian Astronomical Journal 168: 25, Bibcode:2004SerAJ.168...25O, doi:10.2298/saj0468025o. 
  7. ^ a b 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. 
  8. ^ Dibon-Smith, Richard, "z Aquarii", The Constellations Web Page, retrieved 2012-07-10. 
  9. ^ 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. 
  10. ^ 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. 
  11. ^ 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. 
  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)
  13. ^ (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.
  14. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 16 日

External links[edit]