Alpha Mensae

α Mensae

Observation data Epoch J2000      Equinox J2000
Constellation	Mensa
Right ascension	06h 10m 14.47353s
Declination	–74° 45′ 10.9583″
Apparent magnitude (V)	5.09
Characteristics
Spectral type	G7 V
U−B color index	0.33
B−V color index	0.72
V−R color index	0.38
R−I color index	0.32
Astrometry
Radial velocity (Rv)	+34.9 km/s
Proper motion (μ)	RA: 121.80 mas/yr Dec.: −212.34 mas/yr
Parallax (π)	98.06 ± 0.14 mas
Distance	33.26 ± 0.05 ly (10.20 ± 0.01 pc)
Absolute magnitude (MV)	5.05
Details
Mass	1.103 ± 0.086 M☉
Radius	0.99 ± 0.03 R☉
Luminosity (bolometric)	0.832 ± 0.025 L☉
Luminosity (visual, LV)	0.819 L☉
Surface gravity (log g)	4.5 cgs
Temperature	5,587 K
Metallicity [Fe/H]	0.05 dex
Rotational velocity (v sin i)	1.7 km/s
Age	5.4 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.

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, 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% of the mass, 99% 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.

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. 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.