National Geographic : 1952 Feb
255 Mount Wilson and Palomar Observatories Andromeda Nebula, Milky Way's Twin, Whirls 4,500,000,000,000,000,000 Miles Away Our world is a speck in a fiery pinwheel resembling this incandescent spiral. Our medium-sized sun is one of some 200 billion stars lighting the Milky Way. Andromeda Nebula has perhaps a comparable number. Light takes 65,000 years to cross from rim to rim. Two very bright objects are dwarf satellite nebulae which accompany Andromeda. Stars in these nebulae, as in our own galaxy, burn billions of years by atomic fusion, Nature's economical conversion of hydrogen into helium, ash of the universe. Fission, the opposite process, blasts elements apart. If man perfects the hydrogen bomb, he will duplicate the stellar furnaces in miniature.