About the Book
This book consists of articles from Wikia or other free sources online. Pages: 44. Chapters: Comets, Galaxies, Moons, Nebulae, Planets, Stars, Asterism, Intergalactic space, Interstellar medium, Planetesimal, Comet, List of comets, Galaxy, Messier 87, Interplanetary space, Luna, Natural satellite, Planetary ring, Nebula, 2006 definition of planet, Carbon planet, Chthonian planet, Definition of planet, Dwarf planet, Gas giant, Hot Jupiter, Hypothetical planet, Interplanetary space, Interstellar planet, Jupiter, Ocean Planet, Planet, Planetar, Planetary system, Planetesimal, Protoplanet, Protoplanetary disk, Solar nebula, Supergiant planet, Superjovian, Terrestrial planet, Betelgeuse, HD 209458, Interstellar medium, Main sequence, Metallicity, Nemesis, Star, Stellar classification, Sun. Excerpt: In astronomy, an asterism is a pattern of stars seen in Earth's sky which is not an official constellation. Like constellations, they are composed of stars which, while they are in the same general direction, are not physically related, often being at significantly different distances from Earth. An asterism may be composed of stars from one or more constellations. Their mostly simple shapes and few stars make these patterns easy to identify and thus particularly useful to those just learning to orient themselves when viewing the night sky. The visible stars are strewn randomly about the sky. Even before the dawn of civilization, it became common to clump various stars together in connect-the-dots stick-figure patterns. The grouping of stars into constellations is essentially arbitrary, and different cultures have had different constellations, although a few of the more obvious ones tend to recur frequently, e.g., Orion and Scorpius. Historically, without an "official" list, there was really no difference between a constellation and an asterism. Anyone could arrange and name a grouping which might or might not be generally accepted. Still, some of our own constellations...
