16 Aquarii

16 Aquarii, abbreviated 16 Aqr, is a star in the constellation of Aquarius. 16 Aquarii is the Flamsteed designation. It is a faint star, just visible to the naked eye, with an apparent visual magnitude of 5.869.[2] Based upon an annual parallax shift of 9.5 mas,[1] it is located about 342 light years away. It is moving closer to the Earth with a heliocentric radial velocity of −6 km/s,[5] and is predicted to come within 220 light-years in 6.8 million years.[4]

16 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  21h 21m 04.31919s[1]
Declination −04° 33′ 36.4532″[1]
Apparent magnitude (V) 5.869[2]
Characteristics
Spectral type G7 III[3]
B−V color index 0.912±0.001[4]
Astrometry
Radial velocity (Rv)−6.0±2.9[5] km/s
Proper motion (μ) RA: −9.86[6] mas/yr
Dec.: +11.22[6] mas/yr
Parallax (π)9.5319 ± 0.1192[1] mas
Distance342 ± 4 ly
(105 ± 1 pc)
Absolute magnitude (MV)1.08[4]
Details[7]
Mass2.34±0.13 M☉
Radius7.86±0.26 R☉
Luminosity37.4±2.3 L☉
Surface gravity (log g)3.03±0.04 cgs
Temperature5,096±35 K
Metallicity [Fe/H]0.01±0.10 dex
Rotational velocity (v sin i)1.79[8] km/s
Age740±130 Myr
Other designations
BD−05° 5524, HD 203222, HIP 105412, HR 8160, SAO 145317[9]
Database references
SIMBADdata

At the estimated age of 740 million years, this is an aging giant star currently on the red giant branch[7] with a stellar classification of G7 III.[3] This indicates it has exhausted the supply of hydrogen at its core and is generating energy via hydrogen fusion along a shell surrounding a hot core of inert helium. The star has 2.3 times the mass of the Sun and has expanded to 8 times the Sun's radius. It is radiating 37 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,096 K.[7]

References
  1. 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.
  2. Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016), "The PASTEL catalogue: 2016 version", Astronomy & Astrophysics, 591: A118, arXiv:1605.07384, Bibcode:2016A&A...591A.118S, doi:10.1051/0004-6361/201628497.
  3. 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. 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. Gontcharov, G. A. (2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  6. van Leeuwen, F. (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.
  7. Reffert, Sabine; et al. (2015), "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity", Astronomy & Astrophysics, 574: A116, arXiv:1412.4634, Bibcode:2015A&A...574A.116R, doi:10.1051/0004-6361/201322360.
  8. Hekker, S.; Meléndez, J. (2007), "Precise radial velocities of giant stars. III. Spectroscopic stellar parameters", Astronomy and Astrophysics, 475 (3): 1003, arXiv:0709.1145, Bibcode:2007A&A...475.1003H, doi:10.1051/0004-6361:20078233.
  9. "16 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 22, 2018.
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