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[1] mas
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: 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, 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.
  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.
  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, 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.
  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 10, 2012, retrieved 2012-01-16
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