Lambda Centauri

Lambda Centauri (λ Cen, λ Centauri) is a star in the southern circumpolar constellation of Centaurus. It has an apparent visual magnitude of +3.13,[2] which is bright enough to be seen with the naked eye from the Southern Hemisphere and places it among the brighter members of this constellation. The star is close enough that its distance can be determined directly using the parallax technique, which gives a value of roughly 420 light-years (130 parsecs) from Earth, with a 5% margin of error.[1] Although a putative solitary star, it has a candidate proper motion companion at an angular separation of 0.73 arcseconds along a position angle of 135°.[12] The nebula IC 2944 lies nearby.

λ Centauri
Location of λ Centauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 11h 35m 46.88530s[1]
Declination −63° 01′ 11.4313″[1]
Apparent magnitude (V) +3.13[2]
Characteristics
Spectral type B9 III[3][4]
U−B color index −0.19[2]
B−V color index −0.04[2]
Astrometry
Radial velocity (Rv)−1.4[5] km/s
Proper motion (μ) RA: −33.41[1] mas/yr
Dec.: −7.08[1] mas/yr
Parallax (π)7.77 ± 0.34[1] mas
Distance420 ± 20 ly
(129 ± 6 pc)
Absolute magnitude (MV)−2.35[6]
Details
Mass5.1 M☉
Radius5.5[7] R☉
Luminosity739[8] L☉
Surface gravity (log g)3.04[9] cgs
Temperature9,880[10] K
Metallicity [Fe/H]+0.41[9] dex
Rotational velocity (v sin i)183[11] km/s
Other designations
CP−62°2127, FK5 436, HD 100841, HIP 56561, HR 4467, SAO 251472.
Database references
SIMBADdata
λ Centauri in IC 2944, with IC 2948 below left and IC 2872 above right
Lambda Centauri and surrounding nebula IC 2944

Lambda Centauri is a B-type giant star[13] with a stellar classification of B9 III.[3] (Although it has also been classified as A1 III.)[10] It has about 5.5[7] times the radius of the Sun and is rotating rapidly with a projected rotational velocity of 183 km/s.[11] The star's outer atmosphere has an effective temperature of 9,880 K,[10] giving it a blue-white hue.

Crux with λ Centauri and its associated nebulosity visible at the top of the image

Based upon the position and movement of this star through space, it is a likely member of the Gould Belt. In particular, it belongs to the Lower Centaurus-Crux (LCC) group of the Scorpius–Centaurus Association, which is the nearest OB association to the Sun. This is a loose grouping of stars that share a common motion through space and therefore formed in the same molecular cloud. The LCC group has an estimated age of 16–20 million years and is centered on a mean distance of 380 light-years (120 parsecs) from Earth.[14]

References
  1. van Leeuwen, F. (November 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. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
  3. Houk, Nancy (1979), "Michigan catalogue of two-dimensional spectral types for the HD stars", Ann Arbor : Dept. of Astronomy, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, 1, Bibcode:1978mcts.book.....H
  4. 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. Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, University of Toronto: International Astronomical Union, 30: 57, Bibcode:1967IAUS...30...57E
  6. Eggen, O. J. (1984). "The A0 stars". Astrophysical Journal Supplement Series. 55: 597. Bibcode:1984ApJS...55..597E. doi:10.1086/190971.
  7. Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189 (3): 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601
  8. McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental parameters and infrared excesses of Hipparcos stars". Monthly Notices of the Royal Astronomical Society. 427: 343. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x.
  9. Erspamer, D.; North, P. (2003). "Automated spectroscopic abundances of a and F-type stars using echelle spectrographs. II. Abundances of 140 A-F stars from ELODIE". Astronomy and Astrophysics. 398 (3): 1121. arXiv:astro-ph/0210065. Bibcode:2003A&A...398.1121E. doi:10.1051/0004-6361:20021711.
  10. Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147
  11. Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393 (3): 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943
  12. Shatsky, N.; Tokovinin, A. (January 2002), "The mass ratio distribution of B-type visual binaries in the Sco OB2 association", Astronomy and Astrophysics, 382: 92–103, arXiv:astro-ph/0109456, Bibcode:2002A&A...382...92S, doi:10.1051/0004-6361:20011542
  13. O'Meara, Stephen James (2002), The Caldwell Objects, Cambridge University Press, pp. 399–400, ISBN 0-521-82796-5
  14. Bobylev, V. V.; Bajkova, A. T. (September 2007), "Kinematics of the Scorpius-Centaurus OB association", Astronomy Letters, 33 (9): 571–583, arXiv:0708.0943, Bibcode:2007AstL...33..571B, doi:10.1134/S1063773707090010
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