18 Aquarii

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18 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  21h 24m 11.49206s[1]
Declination −12° 52′ 41.1928″[1]
Apparent magnitude (V) 5.49[2]
Spectral type F0 V[3]
B−V color index +0.29[2]
Radial velocity (Rv)−3.0±6.9[4] km/s
Proper motion (μ) RA: +89.60[1] mas/yr
Dec.: +8.62[1] mas/yr
Parallax (π)21.23 ± 0.29 mas
Distance154 ± 2 ly
(47.1 ± 0.6 pc)
Absolute magnitude (MV)2.12[4]
Mass1.54[5] M
Luminosity11.8[4] L
Surface gravity (log g)3.98[6] cgs
Temperature7,194[6] K
Metallicity [Fe/H]–0.16[6] dex
Rotational velocity (v sin i)138[7] km/s
Age480[5] Myr
Other designations
18 Aqr, BD−13° 5923, FK5 1562, HD 203705, HIP 105668, HR 8187, SAO 164364[8]
Database references

18 Aquarii is a single,[9] yellow-white hued star in the equatorial constellation of Aquarius. The designation is from the catalogue of English astronomer John Flamsteed, first published in 1712; the star is faintly visible to the naked eye with an apparent visual magnitude of 5.49[2] and is located about 154 light-years (47 parsecs) from Earth.[1]

This is an F-type main sequence star with a stellar classification of F0 V,[3] it is an estimated 480[5] million years old and has a high rate of spin with a projected rotational velocity of 138 km/s.[7] The star has 1.54[5] times the mass of the Sun and is radiating 11.8[4] times the Sun's luminosity from its photosphere at an effective temperature of 7,194 K.[6]


  1. ^ a b c d e 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 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 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 c d Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  5. ^ a b c d David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  6. ^ a b c d Soubiran, C.; et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247.
  7. ^ a b Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224.
  8. ^ "18 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-02-02.
  9. ^ De Rosa, R. J.; Patience, J.; Wilson, P. A.; Schneider, A.; Wiktorowicz, S. J.; Vigan, A.; Marois, C.; Song, I.; MacIntosh, B.; Graham, J. R.; Doyon, R.; Bessell, M. S.; Thomas, S.; Lai, O. (2014), "The VAST Survey - III. The multiplicity of A-type stars within 75 pc", Monthly Notices of the Royal Astronomical Society, 437 (2): 1216, arXiv:1311.7141, Bibcode:2014MNRAS.437.1216D, doi:10.1093/mnras/stt1932.

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