Alpha Mensae

α Mensae
Location of α Mensae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Mensa
Right ascension 06h 10m 14.47258s[1]
Declination −74° 45′ 10.9583″[1]
Apparent magnitude (V) 5.09[2]
Characteristics
Spectral type G7 V[3] + M3.5-6.5 V[4]
U−B color index 0.33[5]
B−V color index 0.72[5]
Astrometry
Radial velocity (Rv)+34.9[6] km/s
Proper motion (μ) RA: +121.596[1] mas/yr
Dec.: −212.411[1] mas/yr
Parallax (π)97.9158 ± 0.0573 mas[1]
Distance33.31 ± 0.02 ly
(10.213 ± 0.006 pc)
Absolute magnitude (MV)5.03[7]
Details[4]
α Men A
Mass0.964±0.037 M☉
Radius0.960±0.013 R☉
Luminosity0.81±0.02 L☉
Surface gravity (log g)4.459±0.006 cgs
Temperature5,569±50 K
Metallicity [Fe/H]0.11±0.05 dex
Rotational velocity (v sin i)0.6±0.6 km/s
Age6.2±1.4 Gyr
α Men B
Mass0.169±0.006 M☉
Radius0.19±0.01 R☉
Temperature3,054±44 K
Other designations
Alf Men, Alp Men, CD−74°294, FK5 239, GJ 231, HD 43834, HIP 29271, HR 2261, SAO 256274, LTT 2490[8]
Database references
SIMBADdata
ARICNSdata

α Mensae (Latinised as Alpha Mensae, abbreviated to α Men or Alpha Men) 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 96.4% of the mass, 96% of the radius, and 81% of the Sun's luminosity.[4] The effective temperature of the stellar atmosphere is 5,569 K, and it has a slightly higher (129%) proportion of elements other than hydrogen and helium—what astronomers call the star's metallicity—compared to the Sun.[4] The estimated age of this star is 6.2 billion years, and is rotating at a relatively leisurely projected rotational velocity of 0.6 km/s.[4]

Located 33 light years distant from the Sun, Alpha Mensae has a relatively high proper motion across the sky. It has already made its closest approach to the Sun, coming within about 10 ly (3.2 pc) around 250,000 years ago.[9] A candidate infrared excess has been detected around this star, most which would indicate the presence of a circumstellar disk at a radius of over 147 AU. The derived temperature of this dust is below 22 K.[10] However, data from Herschel Space Observatory failed to confirm this excess, leaving the finding in doubt.[11] 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][12][13] With a mass just 16.9% that of the Sun, the companion is fully convective.[4]

  1. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ Cite error: The named reference MERMILLIOD was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference aj132_1_161 was invoked but never defined (see the help page).
  4. ^ a b c d e f Cite error: The named reference Chontos was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference clpl4 was invoked but never defined (see the help page).
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  7. ^ Cite error: The named reference Holmberg2009 was invoked but never defined (see the help page).
  8. ^ a b c Cite error: The named reference simbad_a was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference aa575_A35 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference aa555_A11 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Sibthorpe2018 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference aaa474_273 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference simbad_b was invoked but never defined (see the help page).