20 Persei


20 Persei is a visual binary star in the northern constellation of Perseus, a few degrees from Pi Persei. It is visible to the naked eye as a dim, yellow-white hued point of light with a combined apparent visual magnitude of 5.343.[2] The system is located around 230 light-years (71 pc) away from the Sun, based on its parallax.[1] It is receding from the Earth with a heliocentric radial velocity of +6 km/s.[5]

20 Persei
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus
Right ascension 02h 53m 42.61284s[1]
Declination +38° 20′ 14.9532″[1]
Apparent magnitude (V) 5.343[2]
Spectral type F6V[3]
U−B color index +0.03[4]
B−V color index +0.42[4]
Radial velocity (Rv)5.8 ± 2[5] km/s
Proper motion (μ) RA: 46.79[1] mas/yr
Dec.: -78.90[1] mas/yr
Parallax (π)14.15 ± 0.72 mas[1]
Distance230 ± 10 ly
(71 ± 4 pc)
Period (P)31.633 ± 0.024 a (11,553.9 ± 8.7 d)
Semi-major axis (a)0.2224 ± 0.0011″
Eccentricity (e)0.7560 ±0.0023
Inclination (i)120.48 ± 0.20°
Longitude of the node (Ω)26.62 ± 0.24°
Periastron epoch (T)2450255.5 ± 12
Argument of periastron (ω)
265.54 ± 0.11°
20 Per A
Mass1.5[7] M
20 Per A
Mass1.5[7] M
Other designations
20 Per, BD+37° 655, HD 17904, HIP 13490, HR 855, SAO 55975, WDS J02537+3820
Database references

The orbit of the two stars has been calculated from the secondary changing its position relative to the primary. The two orbit each other every 31.6 years with an angular semimajor axis of 0.22 arcseconds and an eccentricity of 0.7560.[6] The combined spectrum of 20 Persei matches that of an F-type main-sequence star,[3] and the two stars are thought to have equal masses, 1.5 times that of the Sun.[7] A ninth-magnitude star, designated 20 Persei C, may be associated with the pair.[8]


  1. ^ a b c d e f 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. S2CID 18759600. Archived from the original on 2016-04-02.
  2. ^ a b 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. ^ a b Abt, Helmut A. (2009). "MK Classifications of Spectroscopic Binaries". The Astrophysical Journal Supplement Series. 180: 117–118. Bibcode:2009ApJS..180..117A. doi:10.1088/0067-0049/180/1/117.
  4. ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. ^ a b Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
  6. ^ a b Muterspaugh, Matthew W.; Hartkopf, William I.; Lane, Benjamin F.; o'Connell, J.; Williamson, M.; Kulkarni, S. R.; Konacki, Maciej; Burke, Bernard F.; Colavita, M. M.; Shao, M.; Wiktorowicz, Sloane J. (2010). "The Phases Differential Astrometry Data Archive. Ii. Updated Binary Star Orbits and a Long Period Eclipsing Binary". The Astronomical Journal. 140 (6): 1623. arXiv:1010.4043. Bibcode:2010AJ....140.1623M. doi:10.1088/0004-6256/140/6/1623. S2CID 6030289.
  7. ^ a b c Heintz, W. D. (1981). "The Binary System of 20 Persei". Publications of the Astronomical Society of the Pacific. 93: 328. Bibcode:1981PASP...93..328H. doi:10.1086/130832.
  8. ^ "* 20 Per C". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 June 2017.