Eta Crucis

Eta Crucis (η Crucis) is a solitary[10] star in the southern constellation of Crux. It can be seen with the naked eye, having an apparent visual magnitude of 4.14m.[2] Based upon parallax measurements,[1] η Crucis is located 64 light-years from the Sun. The system made its closest approach about 1.6 million years ago when it achieved perihelion at a distance of roughly 26 light years.[11]

η Crucis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Crux
Right ascension  12h 06m 52.89900s[1]
Declination −64° 36′ 49.4244″[1]
Apparent magnitude (V) 4.14[2]
Characteristics
Spectral type F2 V[3]
U−B color index +0.00[2]
B−V color index +0.35[2]
Astrometry
Radial velocity (Rv)+9.0[4] km/s
Proper motion (μ) RA: +33.88[1] mas/yr
Dec.: −37.02[1] mas/yr
Parallax (π)50.62 ± 0.12[1] mas
Distance64.4 ± 0.2 ly
(19.76 ± 0.05 pc)
Absolute magnitude (MV)2.67[5]
Details
Radius1.3[6] R☉
Luminosity7[7] L☉
Surface gravity (log g)4.01[3] cgs
Temperature6,964[5] K
Metallicity [Fe/H]−0.04[3] dex
Rotational velocity (v sin i)46.1±2.3[5] km/s
Age2.53[8] Gyr
Other designations
η Cru, CD−63° 2145, GJ 9388, HD 105211, HIP 59072, HR 4616, SAO 251742.[9]
Database references
SIMBADdata

This is an F-type main sequence star with a stellar classification of F2 V.[3] It has 130%[6] of the Sun's radius and shines with 7[7] times the luminosity of the Sun from an outer atmosphere with an effective temperature of 6,964 K.[5] Observations of the system using the Spitzer Space Telescope show a statistically significant infrared excess of emission at a wavelength of 70μm. This suggests the presence of a circumstellar disk. The temperature of this material is below 70 K.[8]

Eta Crucis has a pair of visual companions. Component B is a magnitude 11.80 star located at an angular separation of 48.30″ along a position angle of 300°, as of 2010. Component C has a magnitude of 12.16 and lies at an angular separation of 35.50″ along a position angle of 194°, as of 2000.[12]

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. Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M.
  3. Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637.
  4. Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
  5. Ammler-von Eiff, M.; Reiners, A. (2012), "New measurements of rotation and differential rotation in A-F stars: Are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724.
  6. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  7. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  8. Beichman, C. A.; et al. (December 2006), "New Debris Disks around Nearby Main-Sequence Stars: Impact on the Direct Detection of Planets", The Astrophysical Journal, 652 (2): 1674–1693, arXiv:astro-ph/0611682, Bibcode:2006ApJ...652.1674B, doi:10.1086/508449.
  9. "eta Cru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-06.
  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.
  11. Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind", Astronomy & Astrophysics, 575: 13, arXiv:1412.3648, Bibcode:2015A&A...575A..35B, doi:10.1051/0004-6361/201425221, A35.
  12. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122: 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  • Kaler, James B., "Eta Crucis", Stars, University of Illinois, retrieved 2016-10-08.
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