**Allen’s Astrophysical Quantities** is the fourth edition of a comprehensive reference book on astrophysical data, edited by Arthur N. Cox. The book compiles data from ninety authors over nine years, revising the original work by C.W. Allen from 1972. The revision was necessary due to the rapid advancements in astrophysics, which made the third edition outdated by 1990. The new edition includes extensive updates, new chapters on infrared, ultraviolet, X-ray, gamma-ray, and neutrino astronomy, as well as expanded sections on stellar evolution, cosmology, and the Earth. The book also features many supplemental tables, including a list of the world's largest optical telescopes. The book is structured into 27 chapters, covering a wide range of topics in astrophysics, including general constants and units, atoms and molecules, spectra, radiation, radio astronomy, infrared astronomy, ultraviolet astronomy, X-ray astronomy, gamma-ray and neutrino astronomy, the Earth, planets and satellites, the solar system, the Sun, normal stars, stars with special characteristics, cataclysmic and symbiotic variables, supernovae, star populations, theoretical stellar evolution, circumstellar and interstellar material, star clusters, the Milky Way and galaxies, quasars and active galactic nuclei, galaxy clusters, cosmology, and incidental tables. The book provides detailed data and references for various astrophysical phenomena, including spectral lines, radiation quantities, atmospheric properties, and the properties of stars, planets, and galaxies. It also includes information on the expansion rate of the universe, the Hubble constant, and the age of the universe. The electronic version of the book is available for interactive use, with many tables and graphs that can be searched, correlated, and interpolated. The book is a valuable resource for astronomers and astrophysicists, offering a comprehensive compilation of data and references for various astrophysical topics. It includes data on the latest discoveries, such as the newly published NIST physical constants, the discovery of a satellite around the asteroid (45) Eugenia, and the latest gamma-ray bursts. The book also acknowledges the contributions of many scientists who provided important information for the compilation. Despite the extensive coverage, some topics are not included due to the complexity of the compilation process. The book is a significant contribution to the field of astrophysics, providing a reliable and up-to-date reference for researchers and students alike.**Allen’s Astrophysical Quantities** is the fourth edition of a comprehensive reference book on astrophysical data, edited by Arthur N. Cox. The book compiles data from ninety authors over nine years, revising the original work by C.W. Allen from 1972. The revision was necessary due to the rapid advancements in astrophysics, which made the third edition outdated by 1990. The new edition includes extensive updates, new chapters on infrared, ultraviolet, X-ray, gamma-ray, and neutrino astronomy, as well as expanded sections on stellar evolution, cosmology, and the Earth. The book also features many supplemental tables, including a list of the world's largest optical telescopes. The book is structured into 27 chapters, covering a wide range of topics in astrophysics, including general constants and units, atoms and molecules, spectra, radiation, radio astronomy, infrared astronomy, ultraviolet astronomy, X-ray astronomy, gamma-ray and neutrino astronomy, the Earth, planets and satellites, the solar system, the Sun, normal stars, stars with special characteristics, cataclysmic and symbiotic variables, supernovae, star populations, theoretical stellar evolution, circumstellar and interstellar material, star clusters, the Milky Way and galaxies, quasars and active galactic nuclei, galaxy clusters, cosmology, and incidental tables. The book provides detailed data and references for various astrophysical phenomena, including spectral lines, radiation quantities, atmospheric properties, and the properties of stars, planets, and galaxies. It also includes information on the expansion rate of the universe, the Hubble constant, and the age of the universe. The electronic version of the book is available for interactive use, with many tables and graphs that can be searched, correlated, and interpolated. The book is a valuable resource for astronomers and astrophysicists, offering a comprehensive compilation of data and references for various astrophysical topics. It includes data on the latest discoveries, such as the newly published NIST physical constants, the discovery of a satellite around the asteroid (45) Eugenia, and the latest gamma-ray bursts. The book also acknowledges the contributions of many scientists who provided important information for the compilation. Despite the extensive coverage, some topics are not included due to the complexity of the compilation process. The book is a significant contribution to the field of astrophysics, providing a reliable and up-to-date reference for researchers and students alike.