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Galaxies - the Milky Way's siblings - offer a surprising variety of forms and colours. Displaying symmetrical spiral arms, glowing red nebulae or diffuse halos, even the image of a galaxy can reveal much about its construction. All galaxies consist of gas, dust and stars, but the effects of gravity, dark matter and the interaction of star formation and stellar explosions all influence their appearances.
Contents
Introduction
Spiral Galaxies
Barred Spiral Galaxies
Elliptical Galaxies
Irregular Galaxies and Interacting Systems
Dwarf Galaxies
Ring Galaxies
Galaxy Groups and Galaxy Clusters
Active Galaxies, Quasars, and Gravitational Lenses