Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Radio astronomy is a sub-field of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, when Karl Jansky observed radiation coming from the Milky Way. Subsequent observations have identified a number of different sources of radio emission, such as stars and galaxies, as well as entirely new classes of objects, such as radio galaxies, quasars, pulsars, and masers. Learn more about radio astronomy, its principles and advantages in this book.