Nu Capricorni

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Nu Capricorni
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Capricornus
Right ascension  20h 20m 39.81562s[1]
Declination −12° 45′ 32.6844″[1]
Apparent magnitude (V) +4.76[2]
Spectral type B9 IV[3] or B9.5 V[4]
U−B color index −0.11[2]
B−V color index −0.04[2]
Radial velocity (Rv)−1.00[5] km/s
Proper motion (μ) RA: +14.74[1] mas/yr
Dec.: −14.32[1] mas/yr
Parallax (π)12.88 ± 0.27[1] mas
Distance253 ± 5 ly
(78 ± 2 pc)
Absolute magnitude (MV)+0.32[6]
ν Cap A
Mass2.37[7] M
Luminosity87[6] L
Surface gravity (log g)3.97[7] cgs
Temperature10,461±356[7] K
Metallicity [Fe/H]−0.15±0.04[6] dex
Rotational velocity (v sin i)24[8] km/s
Age115[7] Myr
Other designations
Alshat, ν Cap, 8 Cap, ADS 13714, BD−13° 5642, HD 193432, HIP 100310, HR 7773, SAO 163468, WDS J20207-1246A[9]
Database references

Nu Capricorni (ν Capricorni, abbreviated Nu Cap, ν Cap) is a binary star[4] in the southern constellation of Capricornus. It is 6.6 degrees north of the ecliptic[citation needed] and so is subject to occultations by the Moon.[10] The system is about 253 light-years from the Sun.

The two components are designated Nu Capricorni A (formally named Alshat /ˈælʃæt/, the traditional name for the system)[11] and B.


ν Capricorni (Latinised to Nu Capricorni) is the system's Bayer designation. The designations of the two components as Nu Capricorni A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[12]

The system bore the traditional name Alshat, from the Arabic الشاة aš-šā[t], meaning 'the sheep' that was to be slaughtered by the adjacent Beta¹ Capricorni (Dabih).[13] In 2016, the IAU organized a Working Group on Star Names (WGSN)[14] to catalog and standardize proper names for stars; the WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[15] It approved the name Alshat for the component Nu Capricorni A on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.[11]


The primary member, Nu Capricorni A, is a blue-white hued B-type main sequence or subgiant star with an apparent magnitude of +4.77. Its companion, Nu Capricorni B, is a magnitude 11.8 star at an angular separation of 54.1 arcseconds from the primary.[4]


  1. ^ a b c d e 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 Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  3. ^ Houk, N.; Smith-Moore, M. (1988), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars, 4,
  4. ^ a b c 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.
  5. ^ 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.
  6. ^ 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.
  7. ^ a b c d David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  8. ^ Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224.
  9. ^ "nu. Cap". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-05-13.
  10. ^ 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.
  11. ^ a b "Naming Stars". Retrieved 16 December 2017.
  12. ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  13. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 142. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  14. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  15. ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.