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
Distance208 ± 3 ly
(63.7 ± 0.9 pc)
Absolute magnitude (MV)−0.46[6]
Surface gravity (log g)3.64[7] cgs
Temperature9,470[7] K
Metallicity [Fe/H]+0.07[7] dex
Rotational velocity (v sin i)70[2] km/s
Age240[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] Based upon parallax measurements taken during the Hipparcos mission, it is approximately 208 light-years (64 pc) from the Sun.[1]


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

It bore the traditional name, Albali, from the Arabic البالع (albāli‘), meaning "the swallower". (See also Albulaan.) Along with Mu Aquarii (Albulaan) and Nu Aquarii (also Albulaan), they were al Bulaʽ (البلع), meaning "the Swallower".[10][11] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] 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 included in the List of IAU-approved Star Names.[9]

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".[13]

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.[14] Consequently, Epsilon Aquarii itself is known as 女宿一 (Nǚ Sù yī, English: the First Star of Girl).[15]


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:0708.1752, 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:1204.2459, 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/0608563, Bibcode:2006ApJ...653..675S, doi:10.1086/508649.
  9. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  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. 53, ISBN 0-486-21079-0, retrieved 2010-12-12.
  12. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  13. ^ 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.
  14. ^ (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.
  15. ^ (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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