Nebulae are interstellar clouds of gas and dust, and the Hubble Space Telescope has revealed the existence of many throughout the Milky Way. Edwin Hubble, for whom the telescope is named, established that clouds existed beyond the Milky Way, but scientists later recognized these as independent galaxies different from nebulae within the Milky Way. According to a popular theory, the solar system is the result of the gravitational collapse of one such primordial nebula.