Astronomy:Gamma2 Normae

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Short description: Evolved K-type star in the constellation Norma


Gamma2 Normae
Observation data
Equinox J2000.0]] (ICRS)
Constellation Norma
Right ascension  16h 19m 50.42227s[1]
Declination −50° 09′ 19.8223″[1]
Apparent magnitude (V) 4.02[2]
Characteristics
Spectral type K0III[3]
U−B color index +1.16[2]
B−V color index +1.08[2]
Astrometry
Radial velocity (Rv)−28.9±0.7[4] km/s
Proper motion (μ) RA: −159.71[1] mas/yr
Dec.: −52.25[1] mas/yr
Parallax (π)25.33 ± 0.20[1] mas
Distance129 ± 1 ly
(39.5 ± 0.3 pc)
Absolute magnitude (MV)1.057[5]
Details
Mass2.16[5] M
Luminosity51[6] L
Surface gravity (log g)2.80[5] cgs
Temperature4,699[5] K
Metallicity [Fe/H]0.23[5] dex
Other designations
γ2 Nor, CD−49° 10536, GC 12216, GJ 9554, HD 146686, HIP 80000, HR 6072, SAO 243643[7]
Database references
SIMBADdata
ARICNSdata

Gamma2 Normae, Latinized from γ2 Nor, is the brightest star in the southern constellation of Norma. Its apparent magnitude is 4.02[2] – making it a faint star but visible to the naked eye. Based upon an annual parallax shift of 25.33 mas as seen from Earth,[1] this star is located roughly 129 light years from the Sun. It is moving closer to the Sun with a radial velocity of −29 km/s.[4]

This is an evolved, yellow-hued giant of spectral type K0 III[3] around 2.16[5] times as massive as the Sun that has swollen to a diameter 10 times that of the Sun.[8] It is a red clump star on the horizontal branch, which indicates it is generating energy through helium fusion at its core.[9] The star is radiating 51[6] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,699 K.[5]

Gamma2 Normae is a close double, with a magnitude 10 companion. The pair has been previously identified as a binary star system,[10] but the second release of Gaia data showed the companion star to be much more distant. Another 16-magnitude star, with a temperature of 5,972 K, is listed 20" away with nearly the same parallax and proper motion as Gamma2 Normae.[11]

γ1 Nor is a yellow supergiant located nearby on the celestial sphere, but is much further away from Earth and nearly a magnitude fainter.

References

  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): 653–64. doi:10.1051/0004-6361:20078357. Bibcode2007A&A...474..653V. 
  2. 2.0 2.1 2.2 2.3 Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99): 99, Bibcode1966CoLPL...4...99J. 
  3. 3.0 3.1 Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode1978mcts.book.....H. 
  4. 4.0 4.1 Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode2006AstL...32..759G. 
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Liu, Y. J. et al. (2007), "The abundances of nearby red clump giants", Monthly Notices of the Royal Astronomical Society 382 (2): 553–66, doi:10.1111/j.1365-2966.2007.11852.x, Bibcode2007MNRAS.382..553L. 
  6. 6.0 6.1 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode2012AstL...38..331A. 
  7. "* gam02 Nor". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+gam02+Nor. 
  8. Kaler, James B.. "Gamma-2 Normae". Stars. University of Illinois. http://stars.astro.illinois.edu/sow/gamma2nor.html. Retrieved 23 March 2015. 
  9. Laney, C. D. et al. (January 2012), "A new Large Magellanic Cloud K-band distance from precision measurements of nearby red clump stars", Monthly Notices of the Royal Astronomical Society 419 (2): 1637–1641, doi:10.1111/j.1365-2966.2011.19826.x, Bibcode2012MNRAS.419.1637L. 
  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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode2008MNRAS.389..869E. 
  11. Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode2018A&A...616A...1G.