Initially identified as a comet, the celestial body later came to be accepted as a planet.[80] Soon after, the planet was named Georgium Sidus by Herschel and was called Herschelium in France. The name Uranus, as proposed by Johann Bode, came into widespread usage after Herschel's death.[81] On the theoretical side of astronomy, the English natural philosopher John Michell first proposed the existence of dark stars in 1783. Michell postulated that if the density of a stellar object became great enough, its attractive force would become so large that even light could not escape.[82] He also surmised that the location of a dark star could be determined by the strong gravitational force it would exert on surrounding stars.