Theta Aquarii

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Theta Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings
Cercle rouge 100%.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]
Characteristics
Spectral type G8 III–IV[3]
U−B color index +0.818[2]
B−V color index +0.983[2]
Astrometry
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
Distance 187 ± 2 ly
(57.5 ± 0.8 pc)
Absolute magnitude (MV) +0.23[3]
Details
Mass 2.39[5] to 2.78[3] M
Radius 12[4] R
Luminosity 72[4] to 83[3] L
Surface gravity (log g) 2.8[4] cgs
Temperature 4,864[4] K
Metallicity [Fe/H] +0.01[4] to +0.09[3] dex
Rotational velocity (v sin i) 1.6[4] km/s
Age 437[3] Myr
Other designations
Ancha, 43 Aquarii, BD–08 5845, FK5 840, HD 211391, HIP 110003, HR 8499, SAO 145991.[6]

Theta Aquarii (θ Aquarii, abbreviated Theta Aqr, θ Aqr), also named Ancha,[7] 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.

Nomenclature[edit]

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 entered in the IAU Catalog of Star Names.[7]

In Chinese, (), meaning Weeping, refers to an asterism consisting of Theta Aquarii and Rho Aquarii.[9] Consequently, Theta Aquarii itself is known as 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]

Properties[edit]

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]

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:0708.1752Freely accessible, 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:0805.2434Freely accessible, 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 -- Star", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-06-30. 
  7. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  8. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016. 
  9. ^ (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. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
  11. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Aquarius
  12. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16. 

External links[edit]