The fourth edition of this book was prepared nine years after the third. The most seriously revised chapters are about the Sun, about the physics of non-stationary stars and especially about X-ray binary stars, about the interstellar medium and the structure of the Galaxy, about galaxies and their constellations. Significant additions were made to the chapters on the solar system in connection with the successes in the study of Venus, Uranus and Halley's comet - the brilliant successes of space methods.