A nebula, from the Latin word for cloud, is a cloud of interstellar dust and gases. . Nebulae have been observed both within the Milky Way galaxy and in other galaxies. These large clouds of mostly hydrogen gas can form stars and planets. Secular scientists believe our solar system formed about 4.6 billion years ago from a nebula. 
Nebulae often feature prominently in commercially available collections of deep-space images, since their colours and shapes are interesting, varied and curiously attractive.