Mensa, constellation in the southern sky at about 6 hours right ascension and 80° south in declination. Mensa is a particularly dim constellation, its brightest star being Alpha Mensae, which has a magnitude of 5.1. This constellation contains some of the Large Magellanic Cloud, a satellite of the Milky Way Galaxy and one of the nearest galaxies to Earth, at a distance of 160,000 light-years. The French astronomer Nicolas Louis de Lacaille formed this constellation in 1754. It was originally called Mons Mensae and represents Table Mountain near Cape Town, S.Af., from which in 1751–52 Lacaille conducted his astronomical observations of the southern sky.