Alpha Mensae

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α Mensae
Observation data
Epoch J2000      Equinox J2000
Constellation Mensa
Right ascension 06h 10m 14.4735s[1]
Declination –74° 45′ 10.963″[1]
Apparent magnitude (V) 5.09
Spectral type G5 V[2]
U−B color index 0.33[3]
B−V color index 0.72[3]
V−R color index 0.38
R−I color index 0.32
Variable type None
Radial velocity (Rv) +34.9[4] km/s
Proper motion (μ) RA: 121.84[1] mas/yr
Dec.: −212.80[1] mas/yr
Parallax (π) 98.54 ± 0.45[1] mas
Distance 33.1 ± 0.2 ly
(10.15 ± 0.05 pc)
Absolute magnitude (MV) 5.05
Mass 0.96 ± 0.086[5] M
Radius 0.99 ± 0.03[6] R
Luminosity 0.832 ± 0.025[5] L
Surface gravity (log g) 4.5[5] cgs
Temperature 5,587[5] K
Metallicity [Fe/H] 0.05[5] dex
Rotational velocity (v sin i) 1.7[5] km/s
Age 5.4[5] 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.[2]

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. It is a main sequence dwarf star only slightly smaller and cooler in temperature than the Sun. 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.

Alpha Mensae has a relatively high proper motion across the sky, and it is located about 33 light years distant from the Sun. No planetary companions have yet been discovered around it. It has a red dwarf companion star at a distance of 3.05 arcseconds (a projected separation of roughly 30 AU).[2][7][8]

See also[edit]


  1. ^ a b c d e Perryman, M. A. C. et al. (1997), "The Hipparcos Catalogue", Astronomy & Astrophysics 323: L49–L52, Bibcode:1997A&A...323L..49P 
  2. ^ a b c "LTT 2490 -- High proper-motion star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-09-11. 
  3. ^ 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. 
  4. ^ Evans, D. S. (June 20–24, 1966). Batten, Alan Henry; Heard, John Frederick, ed. "Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30". University of Toronto: International Astronomical Union. Retrieved 2009-09-10.  |chapter= ignored (help)
  5. ^ a b c d e f g 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.
  6. ^ 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:1002.4268, Bibcode:2010MNRAS.405.1907B, doi:10.1111/j.1365-2966.2010.16575.x 
  7. ^ Eggenberger, A.; Udry, S.; Chauvin, G.; Beuzit, J.-L.; Lagrange, A.-M.; Ségransan, D.; Mayor, M. (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. 
  8. ^ "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]