78 Pegasi

78 Pegasi is a binary star system in the northern constellation of Pegasus. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.93.[2] The system is located approximately 224 light years from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −8 km/s.[6] The double-star nature of this system was discovered by A. G. Clark in 1862. The components of this system orbit each other over a 630-year period with an eccentricity of 0.11.[10]

78 Pegasi
Location of 78 Pegasi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pegasus
Right ascension 23h 43m 59.48560s[1]
Declination 29° 21′ 41.2342″[1]
Apparent magnitude (V) 4.93[2]
(5.07 / 8.10)[3]
Characteristics
Spectral type K0III[4]
U−B color index +0.63[5]
B−V color index +0.96[5]
Astrometry
Radial velocity (Rv)−8.33[6] km/s
Proper motion (μ) RA: +71.10[1] mas/yr
Dec.: -40.58[1] mas/yr
Parallax (π)14.54 ± 0.56[1] mas
Distance224 ± 9 ly
(69 ± 3 pc)
Absolute magnitude (MV)0.75[2]
Orbit[3]
Period (P)630.15 yr
Semi-major axis (a)1.614″
Eccentricity (e)0.112
Inclination (i)60.64°
Longitude of the node (Ω)172.55°
Periastron epoch (T)B 2247.71
Argument of periastron (ω)
(secondary)		241.27°
Details
78 Peg A
Mass1.50[7] M☉
Radius10[7] R☉
Luminosity57.35[2] L☉
Surface gravity (log g)2.62[7] cgs
Temperature4,898[7] K
Metallicity [Fe/H]+0.01[2] dex
Rotational velocity (v sin i)1.1[8] km/s
Other designations
78 Peg, BD+28°4627, GC 32954, HD 222842, HIP 117073, HR 8997, SAO 91457, CCDM J23440+2922AB, WDS J23440+2922AB[9]
Database references
SIMBADdata

The primary member, designated component A, is a magnitude 5.07[3] giant star with a stellar classification of K0III,[4] having exhausted the supply of hydrogen at its core and expanded to 10[7] times the Sun's radius. It is a red clump giant,[11] which indicates it is on the horizontal branch and is generating energy through core helium fusion. It has 1.5[7] times the mass of the Sun and is radiating 57[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,898 K.[7] The secondary companion, component B, is magnitude 8.10.[3]

References
  1. 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. S2CID 18759600. Vizier catalog entry
  2. 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. Vizier catalog entry
  3. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 26 May 2017.
  4. Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
  5. Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers. 42 (2): 443. Bibcode:2014JAVSO..42..443M.Vizier catalog entry
  6. Massarotti, Alessandro; Latham, David W.; Stefanik, Robert P.; Fogel, Jeffrey (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.
  7. Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555–562. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A. Vizier catalog entry
  8. De Medeiros, J. R.; Mayor, M. (1999). "A catalog of rotational and radial velocities for evolved stars". Astronomy and Astrophysics Supplement Series. 139 (3): 433. arXiv:astro-ph/0608248. Bibcode:1999A&AS..139..433D. doi:10.1051/aas:1999401. Vizier catalog entry
  9. "78 Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-08-06.
  10. Malkov, O. Yu.; Tamazian, V. S.; Docobo, J. A.; Chulkov, D. A. (2012). "Dynamical masses of a selected sample of orbital binaries". Astronomy & Astrophysics. 546: A69. Bibcode:2012A&A...546A..69M. doi:10.1051/0004-6361/201219774. Vizier catalog entry
  11. Tautvaišienė, G.; et al. (December 2010), "C, N and O abundances in red clump stars of the Milky Way", Monthly Notices of the Royal Astronomical Society, 409 (3): 1213–1219, arXiv:1007.4064, Bibcode:2010MNRAS.409.1213T, doi:10.1111/j.1365-2966.2010.17381.x, S2CID 119182458.
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