Theta Aquarii

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θ Aquarii
Aquarius constellation map.svg
Red circle.svg
Location of θ Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  22h 16m 50.03635s[1]
Declination –07° 46′ 59.8480″[1]
Apparent magnitude (V) 4.175[2]
Spectral type G8 III–IV[3]
U−B color index +0.818[2]
B−V color index +0.983[2]
Radial velocity (Rv)–13.77 ± 0.17[4] km/s
Proper motion (μ) RA: +118.80[1] mas/yr
Dec.: –22.18[1] mas/yr
Parallax (π)17.40 ± 0.23[1] mas
Distance187 ± 2 ly
(57.5 ± 0.8 pc)
Absolute magnitude (MV)+0.23[3]
Mass2.39[5] to 2.78[3] M
Radius12[4] R
Luminosity72[4] to 83[3] L
Surface gravity (log g)2.8[4] cgs
Temperature4,864[4] K
Metallicity [Fe/H]+0.01[4] to +0.09[3] dex
Rotational velocity (v sin i)1.6[4] km/s
Age437[3] Myr
Other designations
Ancha, 43 Aquarii, BD–08 5845, FK5 840, HD 211391, HIP 110003, HR 8499, SAO 145991.[6]
Database references

Theta Aquarii (θ Aquarii, abbreviated Theta Aqr, θ Aqr), officially named Ancha /ˈæŋkə/[7] (distinguish Ankaa, with the same pronunciation), is a star in the equatorial constellation of Aquarius. Visible to the naked eye at apparent magnitude 4.175,[2] it is located at a distance of around 187 light-years (57 parsecs) from the Sun.[1] Since it is near the ecliptic it can be occulted by the Moon, or very rarely by planets.


θ Aquarii (Latinised to Theta Aquarii) is the star's Bayer designation.

It bore the traditional name Ancha; Medieval Latin for "the haunch". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[8] to catalogue and standardize proper names for stars; the WGSN approved the name Ancha for this star on 12 September 2016, and it is now so included in the List of IAU-approved Star Names.[7]

In Chinese, (), meaning Weeping, refers to an asterism consisting of Theta Aquarii and Rho Aquarii.[9] Consequently, the Chinese name for Theta Aquarii itself is 泣二 (Qì èr, English: the Second Star of Weeping).[10] Possibly, the name Lei, meaning "tears (weeping)" in Chinese, derives from the Chinese name for this star.[11]


Ancha belongs to the spectral class G8 with a luminosity class of III–IV suggesting that, at an age of 437[3] million years, this star is part way between the subgiant and giant stages of its evolution. Estimates of the star's mass range from 2.39[5] to 2.78[3] times the Sun's mass, with a radius of about 12[4] times that of the Sun. It is radiating from 72[4] to 83[3] times as much luminosity as the Sun from its enlarged outer envelope at an effective temperature of 4,864 K.[4] At this heat, the star glows with the yellow hue of a G-type star.[12]


  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 Gutierrez-Moreno, Adelina; et al. (1966). "A System of photometric standards". 1. Publicaciones Universidad de Chile, Department de Astronomy: 1–17. Bibcode:1966PDAUC...1....1G.
  3. ^ a b c d e f g h i Takeda, Yoichi; et al. (August 2008), "Stellar Parameters and Elemental Abundances of Late-G Giants", Publications of the Astronomical Society of Japan, 60 (4): 781–802, arXiv:0805.2434, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781.
  4. ^ a b c d e f g h i j Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  5. ^ a b Pizzolato, N.; Maggio, A.; Sciortino, S. (September 2000), "Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases", Astronomy and Astrophysics, 361: 614–628, Bibcode:2000A&A...361..614P.
  6. ^ "* tet Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-30.
  7. ^ a b "Naming Stars". Retrieved 16 December 2017.
  8. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  9. ^ ‹See Tfd›(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.
  10. ^ ‹See Tfd›(in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2010-08-11 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  11. ^ Richard Hinckley Allen. "Star Names — Their Lore and Meaning".
  12. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16.

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