11 Serpentis

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11 Serpentis
Observation data
Epoch J2000      Equinox J2000
Constellation Serpens
Right ascension  15h 32m 57.93765s[1]
Declination −01° 11′ 11.0412″[1]
Apparent magnitude (V) 5.497[2]
Evolutionary stage horizontal branch[2]
Spectral type K0 III[3]
B−V color index 1.092[2]
Radial velocity (Rv)−16.1±2.8[4] km/s
Proper motion (μ) RA: −17.765[1] mas/yr
Dec.: −42.217[1] mas/yr
Parallax (π)12.0563 ± 0.1290[1] mas
Distance271 ± 3 ly
(82.9 ± 0.9 pc)
Absolute magnitude (MV)0.83[5]
Mass1.27±0.35[6] M
Radius11[7] R
Luminosity50[7] L
Surface gravity (log g)2.48±0.11[6] cgs
Temperature4,767±92[6] K
Metallicity [Fe/H]−0.13[7] dex
[6] Gyr
Other designations
A1 Ser, 11 Ser, BD−00°2982, FK5 3226, GC 20896, HD 138562, HIP 76133, HR 5772, SAO 140596[8]
Database references

11 Serpentis is a single[9] star in the constellation of Serpens, located 271 light years away from the Sun. It has the Bayer designation A1 Serpentis,[10] 11 Serpentis is the Flamsteed designation. This object is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 5.497.[2] It is moving closer to the Earth with a heliocentric radial velocity of −16 km/s.[4]

This is an aging giant star with a stellar classification of K0 III,[3] a star that has used up its core hydrogen and has expanded. It is a red clump giant on the horizontal branch, which indicates it is generating energy through the fusion of helium at its core.[2] 11 Serpentis is 2.75 billion years old with 1.3[6] times the mass of the Sun and has 11[7] times the Sun's radius. It is radiating 50[7] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,767 K.[6]


  1. ^ a b c d e 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. ^ a b c d e Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278.
  3. ^ a b Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, Ann Arbor, Michigan: Department of Astronomy, University of Michigan, 5, Bibcode:1999MSS...C05....0H
  4. ^ a b de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  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. ^ a b c d e f Feuillet, Diane K.; et al. (2016), "Determining Ages of APOGEE Giants with Known Distances", The Astrophysical Journal, 817 (1): 40, Bibcode:2016ApJ...817...40F.
  7. ^ a b c d e 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. ^ "11 Ser". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-21.
  9. ^ Eggleton, P. P.; Tokovinin, A. A. (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. ^ Hoffleit, D. (July 1979), "Discordances in Star Designations", Bulletin d'Information du Centre de Donnees Stellaires (17): 38, Bibcode:1979BICDS..17...38H