High Quality Content by WIKIPEDIA articles! Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. It differs from radar astronomy in that the latter utilizes artificial, rather than natural, radio sources. The initial detection of radio waves from an astronomical object (the Milky Way) was made in the 1930s, but subsequent advances (especially post-World War II) have identified a number of different sources of radio emission. These include stars and galaxies as well as entirely new classes of objects, such as Radio Galaxies, Pulsars and Masers.