With a mass only 80 times that of Jupiter (M J), 2MASS J0523-1403 is the smallest known star undergoing nuclear fusion in its core. For stars with metallicity similar to the Sun, the theoretical minimum mass the star can have and still undergo fusion at the core, is estimated to be about 75 M J. When the metallicity is very low, the minimum star size seems to be about 8.3% of the solar mass, or about 87 M J. Smaller bodies called brown dwarfs, occupy a poorly defined grey area between stars and gas giants.