77 Aquarii

77 Aquarii is a single[9] star located 135 light years away from the Sun in the equatorial constellation of Aquarius. 77 Aquarii is its Flamsteed designation. It is visible to the naked eye as a dim star with a baseline apparent visual magnitude of 5.55.[2] The star is moving closer to the Earth with a heliocentric radial velocity of −35 km/s.[1]

77 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 22h 54m 45.47009s[1]
Declination –16° 16′ 19.0505″[1]
Apparent magnitude (V) 5.55[2]
Characteristics
Evolutionary stage giant
Spectral type K1 III[3]
U−B color index +1.089[2]
B−V color index +1.104[2]
Variable type suspected[4]
Astrometry
Radial velocity (Rv)−34.59±0.16[1] km/s
Proper motion (μ) RA: –222.505[1] mas/yr
Dec.: –88.355[1] mas/yr
Parallax (π)24.1777 ± 0.1211 mas[1]
Distance134.9 ± 0.7 ly
(41.4 ± 0.2 pc)
Absolute magnitude (MV)2.46[5]
Details
Mass1.14[6] M☉
Radius5.79+0.22
−0.21[1] R☉
Luminosity13.347±0.085[1] L☉
Surface gravity (log g)2.8[7] cgs
Temperature4,583+86
−83[1] K
Metallicity [Fe/H]+0.03[7] dex
Rotational velocity (v sin i)3.9[7] km/s
Age7.61[6] Gyr
Other designations
70 Aqr, NSV 14358, BD−17°6619, HD 216640, HIP 113148, HR 8711, SAO 165376[8]
Database references
SIMBADdata

At the estimated age of 7.61[6] billion years old, this is an aging giant star with a stellar classification of K1 III.[3] It is a suspected variable star that ranges in brightness from a maximum of magnitude 5.53 down to 5.60.[4] 77 Aquarii has 1.14[6] times the mass of the Sun and, after exhausting the hydrogen at its core, has expanded to six times the Sun's radius. It is radiating 13.3[1] times the Sun's luminosity from its photosphere at an effective temperature of 4,581 K,[7] giving it the orange-hued glow of a K-type star.[10]

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. Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants", Monthly Notices of the Royal Astronomical Society, 172 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
  3. Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
  4. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  5. 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.
  6. Wittenmyer, Robert A.; Liu, Fan; Wang, Liang; Casagrande, Luca; Johnson, John Asher; Tinney, C. G. (July 2016), "The Pan-Pacific Planet Search. V. Fundamental Parameters for 164 Evolved Stars", The Astronomical Journal, 152 (1): 15, arXiv:1605.00323, Bibcode:2016AJ....152...19W, doi:10.3847/0004-6256/152/1/19, S2CID 55991800, 19.
  7. Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  8. "* 77 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-15.
  9. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  10. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16
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