28 Aquarii

28 Aquarii is a single[9] star located about 560 light years away from the Sun in the zodiac constellation of Aquarius. 28 Aquarii is the Flamsteed designation.[8] It is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 5.6.[2] This object is moving further from the Earth with a heliocentric radial velocity of +8.1 km/s.[5]

28 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  22h 01m 05.01544s[1]
Declination +00° 36′ 16.9787″[1]
Apparent magnitude (V) 5.597[2]
Characteristics
Spectral type K2III[3]
U−B color index +1.40[4]
B−V color index +1.28[4]
Astrometry
Radial velocity (Rv)+8.12±0.1[5] km/s
Proper motion (μ) RA: +6.22[6] mas/yr
Dec.: −11.05[6] mas/yr
Parallax (π)5.7956 ± 0.1557[1] mas
Distance560 ± 20 ly
(173 ± 5 pc)
Details[7]
Mass1.47 M☉
Radius28.15+0.61
−0.93[1] R☉
Luminosity258±8[1] L☉
Surface gravity (log g)2.3 cgs
Temperature4,361 K
Age2.9 Gyr
Other designations
28 Aqr, BD−00° 4296, HD 209128, HIP 108691, HR 8390, SAO 127235[8]
Database references
SIMBADdata

This 2.9[7] billion year old object is an aging giant star with a stellar classification of K2 III.[3] After exhausting the hydrogen at its core, this star evolved off the main sequence and has now expanded to 28[1] times the Sun's radius. It has 1.47 times the mass of the Sun and is radiating 258[1] times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,361 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. Gaia DR2 record for this source at VizieR.
  2. Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
  3. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5". Michigan Spectral Survey. 5: 0. Bibcode:1999MSS...C05....0H.
  4. Johnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99. Bibcode:1966CoLPL...4...99J.
  5. Nidever, David L.; Marcy, Geoffrey W.; Butler, R. Paul; Fischer, Debra A.; Vogt, Steven S. (2002). "Radial Velocities for 889 Late‐Type Stars". The Astrophysical Journal Supplement Series. 141 (2): 503. arXiv:astro-ph/0112477. Bibcode:2002ApJS..141..503N. doi:10.1086/340570.
  6. van Leeuwen, F.; et al. (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. Martig, Marie; Fouesneau, Morgan; Rix, Hans-Walter; Ness, Melissa; Mészáros, Szabolcs; García-Hernández, D. A.; Pinsonneault, Marc; Serenelli, Aldo; Aguirre, Victor Silva; Zamora, Olga (2016). "Red giant masses and ages derived from carbon and nitrogen abundances". Monthly Notices of the Royal Astronomical Society. 456 (4): 3655. arXiv:1511.08203. Bibcode:2016MNRAS.456.3655M. doi:10.1093/mnras/stv2830.
  8. "* 28 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 30 January 2018.
  9. 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.
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