Sigma Aquarii

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

Location of σ Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 22h 30m 38.81546s[1]
Declination –10° 40′ 40.6238″[1]
Apparent magnitude (V) 4.81[2]
Spectral type A0 IVs[3]
U−B color index –0.14[2]
B−V color index –0.08[2]
Radial velocity (Rv) +11[4] km/s
Proper motion (μ) RA: +0.30[1] mas/yr
Dec.: –26.87[1] mas/yr
Parallax (π) 11.26 ± 1.26[1] mas
Distance approx. 290 ly
(approx. 89 pc)
Surface gravity (log g) 3.75[5] cgs
Temperature 10,125[5] K
Rotational velocity (v sin i) 22[5] km/s
Other designations
57 Aquarii, BD–11 5850, FK5 1591, HD 213320, HIP 111123, HR 8573, SAO 165134.[6]
Database references

Sigma Aquarii (σ Aqr, σ Aquarii) is the Bayer designation for a double star in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of 4.81.[2] Based upon parallax measurements, the distance to this star is roughly 290 light-years (89 parsecs).[1]

Sigma Aquarii is an astrometric binary with an orbital period of 654 days.[citation needed] The primary component has a stellar classification of A0 IVs,[3] indicating that it is a subgiant star. This is categorized as an Am star, meaning that it is a chemically peculiar. The spectrum displays at least double the normal abundances of elements like magnesium, aluminum and silicon, while helium and scandium are under-abundant.


  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 Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J. 
  3. ^ a b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819. 
  4. ^ Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington D.C., Bibcode:1953GCRV..C......0W. 
  5. ^ a b c Adelman, S. J.; Young, J. M.; Baldwin, H. E. (February 1984), "Optical region elemental abundance analyses of B and A stars. II - The hot AM stars Omicron Pegasi and Sigma Aquarii and the marginal peculiar A star Nu CANCRI", Monthly Notices of the Royal Astronomical Society, 206: 649–660, Bibcode:1984MNRAS.206..649A, doi:10.1093/mnras/206.3.649. 
  6. ^ "sig Aqr -- Star", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-04. 

External links[edit]