The third edition of Astronomical Spectroscopy examines the physics necessary to understand and interpret astronomical spectra. It offers a step-by-step guide to the atomic and molecular physics involved in providing astronomical spectra starting from the relatively simple hydrogen atom and working its way to the spectroscopy of small molecules.Based on UCL course material, this book uses actual astronomical spectra to illustrate the theoretical aspects of the book to give the reader a feel for such spectra as well as an awareness of what information can be retrieved from them. It also provides comprehensive exercises, with answers given, to aid understanding.

Nearly all information about the Universe comes from the study of light as it reaches us. However, understanding the information contained in this light requires both telescopes capable of resolving it into its component colours and a detailed knowledge of the quantum mechanical behaviour of atoms and molecules. This book, which is based on a third-year undergraduate course taught by the author at University College London, presents the basic atomic and molecular physics necessary to understand and interpret astronomical spectra. It explains how and what kind of information can be extracted from these spectra. Contemporary astronomical spectra are used extensively to study the underlying atomic physics and illustrate the results.

Why record spectra of astronomical objects? -- The nature of spectra -- Atomic hydrogen -- Complex atoms -- Helium spectra -- Alkali atoms -- Spectra of nebulae -- Spectra in magnetic fields -- X-ray spectra -- Line profile -- Molecular structure -- Rotational spectra -- Vibration-rotation spectra -- Electronic spectra of diatomic molecules.

A concise introduction, Optical Astronomical Spectroscopy appeals to the newcomer of astronomical spectroscopy and assumes no previous specialist knowledge. Beginning from the physical background of spectroscopy with a clear explanation of energy levels and spectroscopic notation, the book proceeds to introduce the main techniques of optical spectroscopy and the range of instrumentation that is available. With clarity and directness, it then describes the applications of spectroscopy in modern astronomy, such as the solar system, stars, nebulae, the interstellar medium, and galaxies, giving an immediate appeal to beginners.

Thoroughly illustrated and clearly written, this handbook offers graduate students and active researchers a practical guide to astronomical spectroscopy.