Upsilon Capricorni

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Upsilon Capricorni
Location of υ Capricorni (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Capricornus[1]
Right ascension 20h 40m 02.944s[2]
Declination −18° 08′ 19.17″[3]
Apparent magnitude (V) 5.17[4]
Characteristics
Evolutionary stage asymptotic giant branch[5]
Spectral type M1 III[6]
B−V color index +1.65[4]
Astrometry
Radial velocity (Rv)−12.3±1.6[7] km/s
Proper motion (μ) RA: −22.764 mas/yr[2]
Dec.: −22.170 mas/yr[2]
Parallax (π)5.1719±0.1354 mas[2]
Distance630 ± 20 ly
(193 ± 5 pc)
Absolute magnitude (MV)−1.09[1]
Details
Radius92±4[8] R☉
Luminosity1,283.0±76.5[3] L☉
Temperature3,953+427
−193[3] K
Metallicity [Fe/H]−0.08[1] dex
Other designations
υ Cap, 15 Capricorni, NSV 25208, BD−18°5738, FK5 773, HD 196777, HIP 101984, HR 7900, SAO 163779[9]
Database references
SIMBADdata

Upsilon Capricorni is a solitary,[10] reddish hued star in the southern constellation of Capricornus. Its name is a Bayer designation that is Latinized from υ Capricorni, and abbreviated Upsilon Cap or υ Cap. This star is dimly visible to the naked eye with an apparent visual magnitude of 5.17.[4] The star is about 630 light years away based on parallax,[2] but is drifting closer with a radial velocity of −12 km/s.[7] It is 0.22 degree north of the ecliptic, so is subject to lunar occultations.[11][12]

This is an aging red giant star on the asymptotic giant branch[5] with a stellar classification of M1 III,[6] a star that has exhausted the supply of hydrogen at its core then cooled and expanded. It has 92 times the radius of the Sun[8] and is radiating 1,283 times the luminosity of the Sun[3] from its swollen photosphere at an effective temperature of 3,953 K.[3]

It is a suspected variable star of unknown type with a brightness that has been measured ranging from a peak of 5.19 down to 5.24.[13]

References

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  1. ^ a b c 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. XHIP record for this object at VizieR.
  2. ^ a b c d Vallenari, A.; et al. (Gaia collaboration) (2023), "Gaia Data Release 3. Summary of the content and survey properties", Astronomy and Astrophysics, 674: A1, arXiv:2208.00211, Bibcode:2023A&A...674A...1G, doi:10.1051/0004-6361/202243940, S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ 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.
  4. ^ a b c Barnes, T. G.; et al. (May 1978), "Stellar angular diameters and visual surface brightness. III - an improved definition of the relationship", Monthly Notices of the Royal Astronomical Society, 183 (3): 285–304, Bibcode:1978MNRAS.183..285B, doi:10.1093/mnras/183.3.285.
  5. ^ a b Eggen, Olin J. (July 1992), "Asymptotic giant branch stars near the sun", Astronomical Journal, 104 (1): 275–313, Bibcode:1992AJ....104..275E, doi:10.1086/116239.
  6. ^ a b Houk, N.; Smith-Moore, M. (1988), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars, vol. 4, Bibcode:1988mcts.book.....H.
  7. ^ a b Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  8. ^ a b Baines, Ellyn K.; et al. (May 7, 2025), "Vintage NPOI: New and Updated Angular Diameters for 145 Stars", The Astronomical Journal, 169 (6): 293, arXiv:2506.02912, Bibcode:2025AJ....169..293B, doi:10.3847/1538-3881/adc930, ISSN 1538-3881
  9. ^ "* ups Cap", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2025-08-26.
  10. ^ 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, S2CID 14878976.
  11. ^ White, Nathaniel M.; Feierman, Barry H. (September 1987), "A Catalog of Stellar Angular Diameters Measured by Lunar Occultation", Astronomical Journal, 94: 751, Bibcode:1987AJ.....94..751W, doi:10.1086/114513.
  12. ^ Dunham, D. W.; et al. (March 1973), "The angular diameter of Upsilon Capricorni and an occultation of SAO 118655.", Astronomical Journal, 78: 199–201, Bibcode:1973AJ.....78..199D, doi:10.1086/111398.
  13. ^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.