 With a mass only 80 times that of Jupiter ( MJ ) , 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 MJ . When the metallicity is very low , however , the minimum star size seems to be about 8 @.@ 3 % of the solar mass , or about 87 MJ . Smaller bodies called brown dwarfs , occupy a poorly defined grey area between stars and gas giants . 
 With a mass only 80 times that of Jupiter ( MJ ) , 2MASS J0523 @-@ 1403 <a href='drop_aux' title='1'><mark>is</mark></a>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 MJ . When the metallicity <a href='drop_aux' title='2'><mark>is</mark></a>very low , however , the minimum star size <a href='uninflect' title='3'><mark>seems</mark></a> to be about 8 @.@ 3 % of the solar mass , or about 87 MJ . Smaller bodies called brown dwarfs , occupy a poorly defined grey area between stars and gas giants . 
Wid a mass only 80 times that of Jupiter ( MJ ) , 2MASS J0523 @-@ 1403 the smallest known star undergoing nuclear fusion in its core . fir 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 b about 75 MJ . When da metallicity very low , however , tdaminimum star size seem to be bout 8 @.@ 3 % of thdaolar mass , or aabt87 MJ . Smaller bodies called brown dwarfs , occupy a poorly defined grey area between stars and gas giants .