Radio Telescope

A radio telescope is an instrument built to detect and study radio waves coming from space, combining a specialized antenna, often a large parabolic dish, with a sensitive radio receiver, and serving as the main tool of radio astronomy alongside optical telescopes that instead observe visible light. Because it does not depend on sunlight, a radio telescope can observe day or night, but because cosmic radio signals are extremely faint by the time they reach Earth, the antenna and receiver both need to be very large and very sensitive to register anything useful from planets, stars, nebulae and galaxies. The field began by accident in the early 1930s, when the engineer Karl Guthe Jansky, working at Bell Telephone Laboratories, detected radio waves from space while tracking down interference in telephone lines; the first purpose-built radio telescope followed in 1937, when the amateur radio operator Grote Reber built a 9-meter dish in his backyard in Illinois and carried out sky surveys credited with founding radio astronomy as a formal science.