The revised second edition of this established dictionary contains over 4,300 up-to-date entries covering all aspects of astronomy. Compiled with the help of over 20 expert contributors under the editorship of renowned author and broadcaster Ian Ridpath, A Dictionary of Astronomy covers everything from space exploration and the equipment involved, to astrophysics, cosmology, and the concept of time. The dictionary also includes biographical entries on eminent astronomers, as well as worldwide coverage of observatories and telescopes. Supplementary material is included in the appendices, such as tables of Apollo lunar landing missions and the constellations, a table of planetary data, and numerous other tables and diagrams complement the entries. The entries have been fully revised and updated for this edition, and new entries have been added to reflect the recent developments within the field of astronomy, including magnetic reconnection, Fornax cluster, luminosity density, and Akatsuki. The content is enhanced by entry-level web links, which are listed and regularly updated on a companion website.A Dictionary of Astronomy is an invaluable reference source for students, professionals, amateur astronomers, and space enthusiasts.