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
A2 Aquarii, HR 8982, SAO 165836.[9]
A: BD −18 6358, HD 222574, HIP 116901
B: BD −18 6359, HD 222561, HIP 116904

104 Aquarii is the Flamsteed designation for a double star[10] in the equatorial constellation of Aquarius. 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 c 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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