Thoroughly updated, the fourth edition contains: up-to-date photographs and discoveries including - Hubble Space Telescope images, including central star of NGC 2440; discoveries about Venus and Magellan; and the latest on solar neutrinos, including results from GALLEX and SAGE. Each chapter now repeatedly summarizes and reviews the main ideas, with the inclusion of supercomputer simulations of events, for example, chapter 10 has a simulation of the formation of Mercury.