Radio astronomyradio waves emitted by physical processes occurring in space. Radio waves are much longer than light waves. In order to receive good signals, radio astronomy requires large antennas. Radio astronomy is a relatively new field of astronomical research.
Nikola Tesla in the Colorado Springs lab recorded cosmic waves emitting from interstellar clouds and red giant stars. He observed repeating signals conducted by his transciever. He announced that he received extraterrestrial radio signals. Tesla stated that he received signals from planets in some of the scientific journals of the time. The scientific community did not believe him, primarily because research of cosmic signals did not exist (what is known today as radio astronomy), and the community of science rejected Tesla's data. Tesla spent the latter part of his life trying to signal Mars.
One of the earliest modern investigations into extraterrestrial sources of radio waves were by Karl Guthe Jansky, an engineer with Bell Telephone Laboratories, in the early 1930s. The first object actually detected was the center of the Milky Way, followed by the sun. These early discoveries were confirmed by Grote Reber by 1938. After World War II, substantial improvements in radio astronomy technology were made by astronomers in Europe and the United States, and the field of radio astronomy began to blossom.
Radio astronomy has led to substantial increases in astronomical knowledge, particularly with the discovery of several classes of new objects, including pulsars, quasars and radio galaxies. Such objects represent some of the most extreme and energetic physical processes in the universe.
Radio astronomy is also partly responsible for the idea that dark matter is an important component of our universe; radio measurements of the rotation of galaxies suggest that there is much more mass in galaxies than has been directly observed (see Vera Rubin). The cosmic microwave background radiation was also first detected using radio telescopes. However, radio telescopes have also been used to investigate objects much closer to home, including observations of the Sun and solar activity, and radar mapping of the planets.
The United States government has established an institution to conduct radio astronomy research, titled the National Radio Astronomy Observatory (commonly abbreviated as NRAO). This institution controls various radio telescopes around the United States included the world's largest fully mobile radio telescope, the Green Bank Telescope. The United States government has also set aside a national radio quiet zone for radio astronomy research centered around Green Bank, West Virginia. As a result, Green Bank is now the home of NRAO's primary facility.
See also: Very Long Baseline Interferometry