Alpha Mensae

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α Mensae
Observation data
Epoch J2000      Equinox J2000
Constellation Mensa
Right ascension 06h 10m 14.47353s[1]
Declination –74° 45′ 10.9583″[1]
Apparent magnitude (V) 5.09[2]
Spectral type G7 V[3]
U−B color index 0.33[4]
B−V color index 0.72[4]
V−R color index 0.38
R−I color index 0.32
Radial velocity (Rv) +34.9[5] km/s
Proper motion (μ) RA: 121.80[1] mas/yr
Dec.: −212.34[1] mas/yr
Parallax (π) 98.06 ± 0.14[1] mas
Distance 33.26 ± 0.05 ly
(10.20 ± 0.01 pc)
Absolute magnitude (MV) 5.05
Mass 1.103 ± 0.086[6] M
Radius 0.99 ± 0.03[7] R
Luminosity (bolometric) 0.832 ± 0.025[6] L
Luminosity (visual, LV) 0.819 L
Surface gravity (log g) 4.5[6] cgs
Temperature 5,587[6] K
Metallicity [Fe/H] 0.05[6] dex
Rotational velocity (v sin i) 1.7[6] km/s
Age 5.4[6] Gyr
Other designations
Alp Men, Alf Men, CD −74° 294, FK5 239, GCTP 1468.00, GJ 231, HD 43834, HIP 29271, HR 2261, LTT 2490, SAO 256274.[8]
Database references

Alpha Mensae is the brightest star in the constellation Mensa. At a magnitude of 5.09, it is the dimmest lucida (a constellation's brightest star) in the sky. Due to its declination, on Earth it is best visible from higher latitudes of the southern hemisphere, yet can also be seen, though low in the sky, from just north of the Equator when near its daily arc's highest point, the culmination.

This star has a stellar classification of G7 V,[8] indicating that it is a G-type main sequence star that is generating energy by fusing hydrogen into helium at its core. It is of similar size but slightly cooler than the Sun, with 110%[6] of the mass, 99%[7] of the radius, and 83% of the Sun's luminosity. The effective temperature of the stellar atmosphere is 5,587 K, and it has a slightly higher (112%) proportion of elements other than hydrogen and helium—what Astronomers call the star's metallicity—compared to the Sun. The estimated age of this star is 5.4 billion years, and is rotating at a relatively leisurely projected rotational velocity of 1.7 km/s.[6]

Located about 33 light years distant from the Sun, Alpha Mensae has a relatively high proper motion across the sky. An infrared excess has been detected around this star, most likely indicating the presence of a circumstellar disk at a radius of over 147 AU. The temperature of this dust is below 22 K.[9] No planetary companions have yet been discovered around it. It has a red dwarf companion star at an angular separation of 3.05 arcseconds; equivalent to a projected separation of roughly 30 AU.[8][10][11]


  1. ^ a b c d e van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752free to read. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ^ Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV data. SIMBAD. Bibcode:1986EgUBV........0M. 
  3. ^ Gray, R. O.; et al. (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): 161–70, arXiv:astro-ph/0603770free to read, Bibcode:2006AJ....132..161G, doi:10.1086/504637. 
  4. ^ a b 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. 
  5. ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick. Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E. Retrieved 2009-09-10. 
  6. ^ a b c d e f g h i Valenti, Jeff A.; Fischer, Debra A. (July 2005). "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs". The Astrophysical Journal Supplement Series. 159 (1): 141–166. Bibcode:2005ApJS..159..141V. doi:10.1086/430500.  Note: see VizieR catalogie J/ApJS/159/141.
  7. ^ a b Bruntt, H.; et al. (July 2010), "Accurate fundamental parameters for 23 bright solar-type stars", Monthly Notices of the Royal Astronomical Society, 405 (3): 1907–1923, arXiv:1002.4268free to read, Bibcode:2010MNRAS.405.1907B, doi:10.1111/j.1365-2966.2010.16575.x 
  8. ^ a b c "LTT 2490 -- High proper-motion star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-09-11. 
  9. ^ Eiroa, C.; et al. (July 2013). "DUst around NEarby Stars. The survey observational results". Astronomy & Astrophysics. 555: A11. arXiv:1305.0155free to read. Bibcode:2013A&A...555A..11E. doi:10.1051/0004-6361/201321050. 
  10. ^ Eggenberger, A.; et al. (2007). "The impact of stellar duplicity on planet occurrence and properties. I. Observational results of a VLT/NACO search for stellar companions to 130 nearby stars with and without planets". Astronomy and Astrophysics. 474 (1): 273–291. Bibcode:2007A&A...474..273E. doi:10.1051/0004-6361:20077447. 
  11. ^ "HD 43834B -- Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-03-26.  (details on the stellar properties of the companion star)

External links[edit]

  • "Alpha Mensae". SolStation. Archived from the original on 26 June 2006. Retrieved 2006-07-24. 
  • Kaler, Jim. "Alpha Mensae". Stars. University of Illinois. Retrieved 2014-01-01. 
  • "Gl 231". ARICNS. Archived from the original on 2006-02-20. Retrieved 2006-07-24. 
  • "HD 43834". Alcyone ephemeris. Retrieved 2006-07-24.