Nu2 Sagittarii

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Nu2 Sagittarii
Diagram showing star positions and boundaries of the Sagittarius constellation and its surroundings
Cercle rouge 100%.svg
Location of ν2 Sagittarii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagittarius
Right ascension 18h 55m 07.14098s[1]
Declination −22° 40′ 16.8185″[1]
Apparent magnitude (V) +4.98[2]
Spectral type K1 Ib–II[3]
B−V color index +1.32[2]
Radial velocity (Rv)−109.6[2] km/s
Proper motion (μ) RA: −109.04[1] mas/yr
Dec.: −35.25[1] mas/yr
Parallax (π)11.91 ± 0.52[1] mas
Distance270 ± 10 ly
(84 ± 4 pc)
Absolute magnitude (MV)+0.38[4]
ν2 Sgr A
Mass1.44[2] M
Radius85[5] R
Diameter85[5] D
Luminosity120[2] L
Surface gravity (log g)1.03[6] cgs
Temperature4,244±57[2] K
Metallicity [Fe/H]−0.13[6] dex
Age4.52[2] Gyr
Other designations
ν2 Sgr, 35 Sgr, BD−22° 4915, HD 175190, HIP 92845, HR 7120, SAO 187445[7]
Database references

Nu2 Sagittarii (ν2 Sagittarii) is a binary star[8] system in the zodiac constellation of Sagittarius. It is faintly visible to the naked eye, having an apparent visual magnitude of +4.98.[2] Based upon a small annual parallax shift of 11.91 mas as seen from Earth,[1] this system is located around 270 light years from the Sun. Nu2 Sagittarii has a high peculiar velocity of 86.0+11.6
and is most likely a runaway star system.[3]

The spectrum of the primary component displays a stellar classification of K1 Ib–II,[3] indicating this is a K-type star with a mixed luminosity class of an evolved bright giant/supergiant star. It is a mild barium star, showing an enhanced abundance of s-process elements in its outer atmosphere. This material was most likely acquired during a previous mass transfer from its now white dwarf companion.[9] The primary has an estimated 1.4[2] times the mass of the Sun and has expanded to 85[5] times the Sun's radius.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 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. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal 150 (3): 88, arXiv:1507.01466, Bibcode 2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88.
  3. 3.0 3.1 3.2 Tetzlaff, N. et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society 410 (1): 190–200, arXiv:1007.4883, Bibcode 2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x.
  4. 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.
  5. 5.0 5.1 Pasinetti Fracassini, L. E. et al. (2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy & Astrophysics 367: 521–24, arXiv:astro-ph/0012289, Bibcode 2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  6. 6.0 6.1 Soubiran, C. et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics 515: A111, arXiv:1004.1069, Bibcode 2010A&A...515A.111S, doi:10.1051/0004-6361/201014247.
  7. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  8. 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.
  9. Gomez, A. E. et al. (1997), "Absolute magnitudes and kinematics of barium stars", Astronomy and Astrophysics 319: 881, Bibcode 1997A&A...319..881G.

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