Nebula (Latin: "mist") is a term formerly used in astronomy to denote any object situated beyond the solar system that is seen as a bright or dark area, in contrast to the pointlike images of stars. This definition, adopted at a time when very distant objects could not be resolved into great detail, unfortunately includes two unrelated classes of objects: the extragalactic nebulae, now called galaxies, which are enormous collections of stars and gas; and the galactic nebulae, which are composed of the interstellar medium (the gas between the stars, with its accompanying small solid particles) within a single galaxy.