Astronomy - a fusion of physics, mathematics and the bottomless beauty of the starry sky - has inspired humanity for more than one century to understand its place in the Universe, to search and discover. This vast field of science has its own language, which, however, can be mastered by a person without special education. This book provides an accessible summary of the fundamental ideas of astronomy, as well as modern principles and facts necessary for anyone who wants to learn more about the night sky. You will learn about black holes and gravitational lenses, about pulsars, quasars and much more that amazes the imagination, making people peer into the heavens with keen interest. The articles are arranged in alphabetical order. The book is intended for a wide range of readers, as well as for school and university students.