Iota Centauri

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ι Centauri
Diagram showing star positions and boundaries of the Centaurus constellation and its surroundings
Cercle rouge 100%.svg

Location of ι Centauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 13h 20m 35.81737s[1]
Declination −36° 42′ 44.2447″[1]
Apparent magnitude (V) +2.73[2]
Spectral type A2 V (kA15hA3mA3va)[3]
U−B color index +0.01[2]
B−V color index +0.03[2]
Radial velocity (Rv) +0.1[4] km/s
Proper motion (μ) RA: −341.11[1] mas/yr
Dec.: −86.14[1] mas/yr
Parallax (π) 55.49 ± 0.17[1] mas
Distance 58.8 ± 0.2 ly
(18.02 ± 0.06 pc)
Mass 2.5[5] M
Luminosity 26[6] L
Surface gravity (log g) 4.11[7] cgs
Temperature 8,600[7] K
Metallicity [Fe/H] –0.46[7] dex
Rotational velocity (v sin i) 90.3[8] km/s
Age 0.35[5] Gyr
Other designations
CD−36°8497, GJ 508.1, FK5 496, HD 115892, HIP 65109, HR 5028, SAO 204371.[9]
Database references

Iota Centauri (ι Cen, ι Centauri) is a star in the southern constellation of Centaurus. It carries the rarely applied traditional name Alhakim ("The Wise One"), dervived from the Arabic title Kentaurus al-Hakeem (قنطورس الحكيم), meaning "The Wise Centaur".[10][unreliable source?] Based upon parallax measurements, it lies at a distance of approximately 58.6 light-years (18.0 parsecs) from Earth.[1] Iota Centauri has an apparent visual magnitude of +2.73,[2] making it easily visible to the naked eye.

In Chinese, (Zhǔ), meaning Pillars, refers to an asterism consisting of ι Centauri, υ2 Centauri, υ1 Centauri, a Centauri, ψ Centauri, 4 Centauri, 3 Centauri and 1 Centauri.[11] Consequently, ι Centauri itself is known as 柱十一 (Zhǔ shíyī, English: the Eleventh Star of Pillars.)[12]

The spectrum of ι Centauri matches a stellar classification of A2 V. It is an A-type main sequence star that is generating energy by the nuclear fusion of hydrogen in its core region. This energy is being radiated from the outer envelope of the star at an effective temperature of 8,600 K,[7] giving the star a white hue.[13] It has about 2.5 times the Sun's mass and is roughly 350 million years old.[5] The abundance of elements other than hydrogen and helium, what astronomers term the metallicity, is only 35% of the abundance in the Sun.[7] A weak magnetic field has been tentatively identified with a strength of −77 ± 30 G.[14]

This star has an excess emission of infrared indicating it is surrounded by a circumstellar disk of dust, known as a debris disk. The disk is located within an orbital radius of six Astronomical Units from the star. The dust is unusually luminous for a star this age, suggesting that some process may have recently increased the amount of debris, such as collisions between planetesimals. Alternatively, the planetesimals in this system may have unusual physical properties. As of 2011, a search for planets in this system has thus far been unsuccessful.[5]

Iota Centauri appears to belong to the stellar kinematic group known as IC 2391. This is a group of around 16 co-moving stars that most likely originated in the same molecular cloud at least 45 million years ago.[15]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d 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. 
  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/0603770Freely accessible, Bibcode:2006AJ....132..161G, doi:10.1086/504637 
  4. ^ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W 
  5. ^ a b c d Quanz, Sascha P.; et al. (August 2011), "Searching for Gas Giant Planets on Solar System Scales: VLT NACO/APP Observations of the Debris Disk Host Stars HD172555 and HD115892", The Astrophysical Journal Letters, 736 (2): L32, arXiv:1106.4528Freely accessible, Bibcode:2011ApJ...736L..32Q, doi:10.1088/2041-8205/736/2/L32 
  6. ^ Wyatt, M. C.; et al. (July 2007), "Steady State Evolution of Debris Disks around A Stars", The Astrophysical Journal, 663 (1): 365–382, arXiv:astro-ph/0703608Freely accessible, Bibcode:2007ApJ...663..365W, doi:10.1086/518404 
  7. ^ a b c d e Saffe, C.; et al. (October 2008), "Spectroscopic metallicities of Vega-like stars", Astronomy and Astrophysics, 490 (1): 297–305, arXiv:0805.3936Freely accessible, Bibcode:2008A&A...490..297S, doi:10.1051/0004-6361:200810260 
  8. ^ Díaz, C. G.; et al. (July 2011), "Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum", Astronomy & Astrophysics, 531: A143, arXiv:1012.4858Freely accessible, Bibcode:2011A&A...531A.143D, doi:10.1051/0004-6361/201016386 
  9. ^ "LTT 5138 -- High proper-motion Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-02-02 
  10. ^ (Turkish) YILDIZ ADLARI SÖZLÜĞÜ - Mustafa Pultar (Alhakim)
  11. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  12. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 25 日
  13. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16 
  14. ^ Hubrig, S.; et al. (February 2006), "Accurate magnetic field measurements of Vega-like stars and Herbig Ae/Be stars", Astronomy and Astrophysics, 446 (3): 1089–1094, arXiv:astro-ph/0510157Freely accessible, Bibcode:2006A&A...446.1089H, doi:10.1051/0004-6361:20053794 
  15. ^ Nakajima, Tadashi; Morino, Jun-Ichi; Fukagawa, Misato (September 2010), "Potential Members of Stellar Kinematical Groups within 20 pc of the Sun", The Astronomical Journal, 140 (3): 713–722, Bibcode:2010AJ....140..713N, doi:10.1088/0004-6256/140/3/713