104 Aquarii

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104 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 23h 41m 45.80611s[1]
Declination –17° 48′ 59.5110″[1]
Apparent magnitude (V) 4.801[2]
Spectral type G2Ib/II[3]
U−B color index +0.521[2]
B−V color index +0.834[2]
Radial velocity (Rv) +3.2[4] km/s
Proper motion (μ) RA: +14.18[1] mas/yr
Dec.: +0.94[1] mas/yr
Parallax (π) 3.89 ± 0.25[1] mas
Distance 840 ± 50 ly
(260 ± 20 pc)
Absolute magnitude (MV) –1.75[5]
104 Aqr A
Mass 4.23[5] M
Radius 51–88[6] R
Luminosity 447[5] L
Surface gravity (log g) 1.8[7] cgs
Temperature 5,478[7] K
Metallicity [Fe/H] +0.05[7] dex
Rotational velocity (v sin i) 15[8] km/s
Age 135[5] Myr
Other designations
HR 8982, SAO 165836.[9]
A: BD −18 6358, HD 222574, HIP 116901
B: BD −18 6359, HD 222561, HIP 116904

104 Aquarii (abbreviated 104 Aqr) is a star in the equatorial constellation of Aquarius. 104 Aquarii is the Flamsteed designation although it also bears the Bayer designation A2 Aquarii. Based on an annual parallax shift of only 3.89 ± 0.25 milliarcseconds, the distance to this star is about 840 light-years (260 parsecs).[1] At that range, the brightness of the star in the V-band is reduced by 0.10 magnitudes as a result of extinction caused by intervening gas and dust.[5]

This is a double star and possible binary system.[10] The primary component has a stellar classification of G2Ib/II,[3] which places it on the borderline between the bright giant and lower luminosity supergiant stars. With more than four times the mass of the Sun,[5] this is an evolved star that has reached its current stage after only 135 million years.[5] It has expanded to around 51–88[6] times the Sun's radius and is radiating 447–fold[5] the luminosity of the Sun. This energy is being emitted from its outer atmosphere at an effective temperature of 5,478 K,[7] giving it the golden-hued glow of a G-type star.[11] It is a suspected variable star.[12]

The companion is a magnitude 7.9 star with an angular separation of 120.1 arcseconds from the primary.[10]


  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 Celis S., L. (October 1975). "Photoelectric photometry of late-type variable stars". Astronomy and Astrophysics Supplement Series 22: 9–17. Bibcode:1975A&AS...22....9C. 
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988MSS...C04....0H. 
  4. ^ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953QB901.W495...... 
  5. ^ a b c d e f g h Takeda, Yoichi; Sato, Bun'ei; Murata, Daisuke (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. 
  6. ^ a b Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451. 
  7. ^ a b c d Luck, R. E.; Bond, H. E. (October 1980), "The chemical compositions of 26 distant late-type supergiants and the metallicity gradient in the galactic disk", Astrophysical Journal, Part 1 241: 218–228, Bibcode:1980ApJ...241..218L, doi:10.1086/158334. 
  8. ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago 239 (1), Bibcode:1970CoAsi.239....1B. 
  9. ^ "104 Aqr -- Star in double system", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-07-16 
  10. ^ a b Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x. 
  11. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16. 
  12. ^ Demartino, Robert; et al. (April 1996), "Accurate Positions Of Suspected Variable Stars Near The South Galactic Pole", Information Bulletin on Variable Stars 4322: 1, Bibcode:1996IBVS.4322....1D. 

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