21 Aquarii
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Aquarius
Right ascension 21h 25m 16.95755s[1]
Declination −03° 33′ 24.2964″[1]
Apparent magnitude (V) 5.48[2]
Characteristics
Spectral type K4III[3]
B−V color index 1.451±0.011[2]
Astrometry
Radial velocity (Rv)−24.5±2[4] km/s
Proper motion (μ) RA: −12.061[1] mas/yr
Dec.: −69.973[1] mas/yr
Parallax (π)7.8747 ± 0.2182 mas[1]
Distance410 ± 10 ly
(127 ± 4 pc)
Absolute magnitude (MV)0.11[2]
Details
Radius28.01+1.09
−2.12[1] R☉
Luminosity203.4±6.4[1] L☉
Surface gravity (log g)1.79[5] cgs
Temperature4119+165
−78[1] K
Metallicity [Fe/H]−0.08[5] dex
Other designations
BD−04°5446, FK5 3708, HD 203926, HIP 105767, HR 8199, SAO 145384
Database references
SIMBADdata

21 Aquarii is a single[6] star in the zodiac constellation of Aquarius. 21 Aquarii is the Flamsteed designation. It is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 5.49.[2] This object is a member of the HR 1614 moving group,[7] and is moving closer to the Earth with a heliocentric radial velocity of −24.5 km/s.[4]

This object is an evolved giant star with a stellar classification of K4 III.[3] As a result of having exhausted the hydrogen at its core, it has expanded to 27[1] times the radius of the Sun. The star is radiating 203[1] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,120 K.[1]

References

  1. ^ a b c d e f g h i j k Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. ^ 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, S2CID 119257644.
  3. ^ a b Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
  4. ^ a b Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
  5. ^ a b McWilliam, Andrew (December 1990). "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances". Astrophysical Journal Supplement Series. 74: 1075–1128. Bibcode:1990ApJS...74.1075M. doi:10.1086/191527.
  6. ^ Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  7. ^ Eggen, Olin J.; Iben, Icko Jr. (April 1991), "First giant branch and asymptotic giant branch stars in nearby aggregates", Astronomical Journal, 101: 1377–1407, Bibcode:1991AJ....101.1377E, doi:10.1086/115773.
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