108 Aquarii

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108 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 23h 51m 21.33832s[1]
Declination –18° 54′ 32.9937″[1]
Apparent magnitude (V) 5.194[2]
Spectral type Ap[3]
U−B color index –0.396[2]
B−V color index –0.135[2]
Variable type α² CVn[4]
Radial velocity (Rv) +12.7[5] km/s
Proper motion (μ) RA: +26.82[1] mas/yr
Dec.: –4.27[1] mas/yr
Parallax (π) 10.23 ± 0.31[1] mas
Distance 319 ± 10 ly
(98 ± 3 pc)
Absolute magnitude (MV) +0.08[6]
Mass 3.21 ± 0.15[6] M
Radius 2.5 ± 0.3[6] R
Luminosity 132[6] L
Surface gravity (log g) 4.27 ± 0.10[6] cgs
Temperature 12,274[6] K
Metallicity [Fe/H] +0.90[7] dex
Rotation 3.74 days[6]
Rotational velocity (v sin i) 30[8] km/s
Other designations
ET Aquarii, i3 Aquarii, BD–19 6522, HD 223640, HIP 117629, HR 9031, SAO 165918.[4]
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

108 Aquarii (ET Aquarii or i3 Aquarii) is the Flamsteed designation for a star in the equatorial constellation of Aquarius. It has an apparent visual magnitude of 5.194[2] and can be seen with the naked eye under suitably dark skies. Based upon an annual parallax shift of 10.23[1] (with a 3% margin of error), the distance to this star is 319 light-years (98 parsecs).

This is an Ap star; meaning it has a peculiar spectrum that shows an overabundance of certain elements. It has more than three times the mass of the Sun and is 2.5 times the Sun's radius.[6] 108 Aquarii is radiating 132[6] times the luminosity of the Sun from its outer atmosphere at an effective temperature of 12,274 K.[6] At this heat, the star has the white hue of an A-type star.[9]


  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, pp. 1–17, Bibcode:1966PDAUC...1....1G. 
  3. ^ Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H. 
  4. ^ a b "ET Aqr -- Variable Star of alpha2 CVn type", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-07-15. 
  5. ^ Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W. 
  6. ^ a b c d e f g h i j North, P. (June 1998), "Do SI stars undergo any rotational braking?", Astronomy and Astrophysics 334: 181–187, arXiv:astro-ph/9802286, Bibcode:1998A&A...334..181N. 
  7. ^ Vilhu, O.; Tuominen, I. V.; Boyarchuk, A. A. (1976), "Abundance Studies of Peculiar B Stars", in Weiss, W. W.; Jenkner, H.; Wood, H. J., Physics of Ap Stars, Proceedings of IAU Colloq. 32, held in Vienna, Austria, 8-11 September, 1976, Universitatssternwarte Wien, p. 563, Bibcode:1976paps.coll..563V. 
  8. ^ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590. 
  9. ^ Przybylski, A.; Kennedy, P. M. (1965), "Radial velocities and three-colour photometry of 166 southern stars", Monthly Notices of the Royal Astronomical Society 131: 95, Bibcode:1965MNRAS.131...95P. 

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