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5 Serpentis is a wide binary star[9] system in Serpens Caput, the western section of the equatorial constellation of Serpens. It is faintly visible to the naked eye with an apparent visual magnitude of 5.10.[2] Based upon an annual parallax shift of 39.40±0.29 mas[1] as viewed from Earth's orbit, it is located 83 light years away. The brighter member is an IAU radial velocity standard star,[10] and it is moving away from the Sun with a heliocentric radial velocity of +54.3 km/s.[5] The system made its closest approach to the Sun about 153,000 years ago at a separation of 68 ly (20.7 pc).[6]

5 Serpentis
Observation data
Epoch J2000      Equinox J2000
Constellation Serpens
Right ascension  15h 19m 18.79710s[1]
Declination +01° 45′ 55.4685″[1]
Apparent magnitude (V) 5.10[2]
Spectral type F8 IV[3][4]
B−V color index 0.50[2]
Radial velocity (Rv)+54.3±0.1[5] km/s
Proper motion (μ) RA: +372.21[1] mas/yr
Dec.: −513.59[1] mas/yr
Parallax (π)39.40 ± 0.29[1] mas
Distance82.8 ± 0.6 ly
(25.4 ± 0.2 pc)
Absolute magnitude (MV)3.02[6]
5 Ser A
Mass1.16[2] M
Luminosity5[2] L
Surface gravity (log g)4.07[4] cgs
Temperature6,025±177[2] K
Metallicity [Fe/H]+0.02[7] dex
Rotational velocity (v sin i)4.8[4] km/s
Age5.27[2] Gyr
Other designations
5 Ser, MQ Ser, BD+02° 2944, HD 136202, HIP 74975, HR 5694, SAO 120946, WDS J15193+0146A[8]
Database references

The primary, component A, is an F-type subgiant star with a stellar classification of F8 IV,[3][4] a star that has exhausted its core hydrogen and is evolving to become a red giant. The star was once thought to be a BY Draconis variable with the variable star designation MQ Ser,[11] but has been found not to be.[12] From observations made between 1975 and 1980, Bakos (1983) reported random, small brightness variations with an amplitude of less than 0.03 magnitude, plus three flare events that increased the brightness by 0.1 magnitudes.[13] However, Scarfe (1985) noted that these observations may instead be due to normal observational error.[10]

The common proper motion companion, component B, is a magnitude 10.11 star at an angular separation of 11.4″ along a position angle of 35°. It has an estimated orbital period of 3,371 years.[9] According to Hoffleit (1991), if this is a variable star it may account for the observations of Bakos (1983).[14]


  1. ^ a b c d e f 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.
  2. ^ a b c d e f g Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, 88.
  3. ^ a b Gray, R. O.; et al. (2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars", The Astronomical Journal, 121 (4): 2148–2158, Bibcode:2001AJ....121.2148G, doi:10.1086/319956.
  4. ^ a b c d Mallik, Sushma V.; et al. (October 2003), "Lithium and rotation in F and G dwarfs and subgiants", Astronomy and Astrophysics, 409: 251–261, Bibcode:2003A&A...409..251M, doi:10.1051/0004-6361:20031084.
  5. ^ a b Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  6. ^ a b 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.
  7. ^ Maldonado, J.; et al. (May 2012), "Metallicity of solar-type stars with debris discs and planets⋆", Astronomy & Astrophysics, 541: 10, arXiv:1202.5884, Bibcode:2012A&A...541A..40M, doi:10.1051/0004-6361/201218800, A40.
  8. ^ "5 Ser". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-03-17.
  9. ^ a b Tokovinin, Andrei (April 2014), "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs", The Astronomical Journal, 147 (4): 14, arXiv:1401.6827, Bibcode:2014AJ....147...87T, doi:10.1088/0004-6256/147/4/87, 87.
  10. ^ a b Scarfe, C. D. (August 1985), "On the Velocity Variability of 5-SERPENTIS and Omicron-Aquilae", Journal of the Royal Astronomical Society of Canada, 79 (595): 180, Bibcode:1985JRASC..79..180S.
  11. ^ Kholopov, P. N.; et al. (1985), "The 67th Name-List of Variable Stars", Information Bulletin on Variable Stars, 2681: 1, Bibcode:1985IBVS.2681....1K.
  12. ^ VSX; Otero, S. A. (13 November 2011). "MQ Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 18 July 2014.
  13. ^ Bakos, G. A. (May 1983), "Flare activity in two F-type stars, 5 Ser and ο Aql", Astronomical Journal, 88: 674–677, Bibcode:1983AJ.....88..674B, doi:10.1086/113357.
  14. ^ Hoffleit, Dorrit (October 1991), "MQ Serpentis, A Mystery", The Journal of the American Association of Variable Star Observers, 20 (2): 239–240, Bibcode:1991JAVSO..20..239H.