Eta Normae

Eta Normae, Latinized from η Normae, is a single[8] star in the southern constellation of Norma. It is visible to the naked eye as a faint, yellow-hued star with an apparent visual magnitude of 4.65.[3] The distance to this star is about 219 light years, based on parallax.[1] The Gamma Normids radiate from a position near this star.[9]

Eta Normae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Norma
Right ascension  16h 03m 12.89783s[1]
Declination −49° 13′ 46.9151″[2]
Apparent magnitude (V) 4.65[3]
Characteristics
Evolutionary stage horizontal branch
Spectral type G8III[4]
U−B color index +0.64[3]
B−V color index +0.92[3]
Astrometry
Radial velocity (Rv)−0.3±2.8[5] km/s
Proper motion (μ) RA: 42.05[1] mas/yr
Dec.: 9.14[1] mas/yr
Parallax (π)14.86 ± 0.25[1] mas
Distance219 ± 4 ly
(67 ± 1 pc)
Absolute magnitude (MV)0.524[6]
Details
Mass2.78[6] M☉
Radius11.07+0.23
−0.09[7] R☉
Luminosity71.9±3.1[7] L☉
Surface gravity (log g)2.84[6] cgs
Temperature5052+16
−51[7] K
Metallicity [Fe/H]−0.05[6] dex
Other designations
η Nor, CD−48° 10512, HD 143546, HIP 78639, HR 5962, SAO 226466[2]
Database references
SIMBADdata

This is an aging giant star with a stellar classification of G8III,[4] having exhausted the supply of hydrogen at its core then swollen and cooled off the main sequence. At present it has 11[7] the girth of the Sun. It is a red clump[6] giant, meaning it is on the horizontal branch and is generating energy through core helium fusion. The star has 2.78[6] times the mass of the Sun and is radiating 72[7] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,052 K.[7] It is a source for X-ray emission.[10]

References
  1. 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. "eta Nor". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-12.
  3. 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.
  4. Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  5. 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.
  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, Bibcode:2007MNRAS.382..553L, doi:10.1111/j.1365-2966.2007.11852.x.
  7. 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.
  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. Lunsford, Robert (2009), Meteors and How to Observe Them, Astronomers' Observing Guides, Springer Science & Business Media, pp. 76–77, ISBN 9780387094618.
  10. Haakonsen, Christian Bernt; Rutledge, Robert E. (September 2009), "XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources", The Astrophysical Journal Supplement, 184 (1): 138–151, arXiv:0910.3229, Bibcode:2009ApJS..184..138H, doi:10.1088/0067-0049/184/1/138.
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