Discoveries in astronomy challenge our fundamental ideas about the universe. Where the astronomers of antiquity once spoke of fixed stars, we now talk of whirling galaxies and giant supernovae. We once thought Earth was the centre of the universe; we now see it as a minor planet among millions of other planetary systems, any number of which could also hold life. These dramatic shifts in our perspective hinge on thousands of personal discoveries: moments when it became clear to someone that some part of the universe, whether a planet or a supermassive black hole, was not as it once seemed. This book invites us to participate in these moments of revelation and wonder as scientists first experienced them. The author, an astronomer, here provides an ambitious and exciting overview of astronomy, conveying to newcomers and enthusiasts alike the most important discoveries of this science and introducing the many people who made them. Illustrated with more than 400 colour images, the book outlines in seventy episodes what humankind has learned about the cosmos and what scientists around the world are poised to learn in the coming decades. Arranged by types of discovery, it also provides an overarching narrative that explains how the earliest ideas of the cosmos evolved into the cutting edge astronomy we know today. Along the way, he never forgets that science is a human endeavour and that every discovery was the result of inspiration, hard work, or luck, usually all three. The first section explores discoveries made before the advent of the telescope, from stars and constellations to the position of our sun. The second considers discoveries made within our solar system, from the phases of Venus and the moons of Jupiter to the comets and asteroids at its distant frontier. The following section delves into discoveries of the dynamic universe, like gravitation, relativity, pulsars, and black holes. A fourth examines findings made within our galaxy, from interstellar nebulae and supernovae to Cepheid variable stars and extrasolar planets. Next, the author turns to discoveries made within the deepest recesses of the universe, like quasars, supermassive black holes, and gamma-ray bursters. In the end, he unveils where astronomy still teeters on the edge of discovery, considering the dark matter and alien life.