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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