The limit of 13 Jupiter masses is not universally accepted. Objects below this mass limit can sometimes burn deuterium, and the amount of deuterium that is burned depends on an object's composition. Furthermore, deuterium is quite scarce, so the stage of deuterium burning does not actually last very long; unlike hydrogen burning in a star, deuterium burning does not significantly affect the future evolution of an object. The relationship between mass and radius (or density) show no special feature at this limit, according to which brown dwarfs have the same physics and internal structure as lighter Jovian planets, and would more naturally be considered planets.