text: which one is more massive: a brown dwarf or a white dwarf? and which one is denser?   a white dwarf is both more massive and denser than a brown dwarf.   a white dwarf was once a fully-qualified ordinary star, producing energy from nuclear fusion.   but a brown dwarf was never massive enough for nuclear fusion to start.   density of a white dwarf about 2 tonnes/cc.   mass; within an order of magnitude the mass of the sun.   density of brown dwarf; a few grams/cc.   mass less than a fiftieth that of the sun.