Epsilon Aquarii

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Epsilon Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings
Cercle rouge 100%.svg

Location of ε Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 20h 47m 40.55260s[1]
Declination −09° 29′ 44.7877″[1]
Apparent magnitude (V) 3.77[2]
Spectral type A1 V[2]
U−B color index +0.029[3]
B−V color index –0.001[3]
Variable type Suspected[4]
Radial velocity (Rv) –16[5] km/s
Proper motion (μ) RA: +33.98[1] mas/yr
Dec.: -34.77[1] mas/yr
Parallax (π) 15.70 ± 0.21[1] mas
Distance 208 ± 3 ly
(63.7 ± 0.9 pc)
Absolute magnitude (MV) −0.46[6]
Surface gravity (log g) 3.64[7] cgs
Temperature 9,470[7] K
Metallicity [Fe/H] +0.07[7] dex
Rotational velocity (v sin i) 70[2] km/s
Age 240[8] Myr
Other designations
Albali, 2 Aquarii, BD-10° 5506, FK5 781, HD 198001, HIP 102618, HR 7950, SAO 144810.[4]
Database references

Epsilon Aquarii (ε Aquarii, abbreviated Epsilon Aqr, ε Aqr), also named Albali,[9] is a star in the equatorial zodiac constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of 3.77.[2] The distance to this star can be determined from parallax measurements, yielding an estimated value of around 208 light-years (64 pc) from the Sun.[1]


ε Aquarii (Latinised to Epsilon Aquarii) is the star's Bayer designation.

This star bore an obscure traditional name, Albali, from the Arabic البالع (albāli‘), meaning "the swallower". (See also Albulaan.) In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, it was designated Nir Saad Bula (نير سعد ألبلع - nayyir sa'd al bulaʽ), which was translated into Latin as Lucida Fortunæ Dissipantis, meaning "the brightest of luck of the swallower".[10] This star, along with Mu Aquarii (Albulaan) and Nu Aquarii (also Albulaan), were al Bulaʽ (البلع), meaning "the Swallower".[11][12][13] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[14] to catalogue and standardize proper names for stars. The WGSN approved the name Albali for this star on 12 September 2016, and it is now so entered in the IAU Catalog of Star Names.[9]

In Chinese, 女宿 (Nǚ Sù), meaning Girl (asterism), refers to an asterism consisting of Epsilon Aquarii, Mu Aquarii, 4 Aquarii, 5 Aquarii and 3 Aquarii.[15] Consequently, Epsilon Aquarii itself is known as 女宿一 (Nǚ Sù yī, English: the First Star of Girl.)[16]


Epsilon Aquarii is an A-type main sequence star with a stellar classification of A1 V.[2]


  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:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e Levato, O. H. (August 1972), "Rotational Velocities and Spectral Types of Some A-Type Stars", Publications of the Astronomical Society of the Pacific, 84 (500): 584, Bibcode:1972PASP...84..584L, doi:10.1086/129336. 
  3. ^ a b Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars, 8: 59, Bibcode:1984SAAOC...8...59C. 
  4. ^ a b "* eps Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-29. 
  5. ^ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W. 
  6. ^ Ammler-von Eiff, M.; Reiners, A. (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459Freely accessible, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724. 
  7. ^ a b c Hill, G. M. (February 1995), "Compositional differences among the A-type stars. 2: Spectrum synthesis up to V sin i = 110 km/s", Astronomy and Astrophysics, 294 (2): 536–546, Bibcode:1995A&A...294..536H. 
  8. ^ Su, K. Y. L.; et al. (December 2006), "Debris Disk Evolution around A Stars", The Astrophysical Journal, 653 (1): 675–689, arXiv:astro-ph/0608563Freely accessible, Bibcode:2006ApJ...653..675S, doi:10.1086/508649. 
  9. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  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. 
  11. ^ 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. 
  12. ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 53, ISBN 0-486-21079-0, retrieved 2010-12-12. 
  13. ^ ε Aqr as Nir Saad Bula or Lucida Fortunæ Dissipantis (the brightest of luck of the swallower) and the common name is Albali. Mu Aquarii and Nu Aquarii was already designated as the common name Albulaan, the plural form of al Bulaʽ
  14. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016. 
  15. ^ (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.
  16. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived October 25, 2008, at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.

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