Book Description: This volume collects an enormous amount of reference information for astronomers and astrophysicists, ranging from fundamental physical constants to orbital data for selected asteroids. For the Earth and planets, it includes, for example, data on mass, orbits, and atmospheres. There are chapters on the Sun, on stars in general, on bright and nearby stars, and on Wolf-Rayet stars. On a large scale, there are data on star clusters and associations, on region of star formation, and other nebulae of various kinds. Finally, the book includes chapters on dwarf stars, pulsars, interacting binaries, symbiotic stars, supernovae remnants, and x-ray and gamma-ray sources. A companion volume Astrophysical Data: Galaxies will follow.