Radio telescope

Directional radio antenna used in radio astronomy / From Wikipedia, the free encyclopedia

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A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky.[1][2][3] Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are the main observing instrument used in traditional optical astronomy which studies the light wave portion of the spectrum coming from astronomical objects. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night.

The 64-meter radio telescope at Parkes Observatory as seen in 1969, when it was used to receive live televised video from Apollo 11
Antenna of UTR-2 low frequency radio telescope, Kharkiv region, Ukraine. Consists of an array of 2040 cage dipole elements.

Since astronomical radio sources such as planets, stars, nebulas and galaxies are very far away, the radio waves coming from them are extremely weak, so radio telescopes require very large antennas to collect enough radio energy to study them, and extremely sensitive receiving equipment. Radio telescopes are typically large parabolic ("dish") antennas similar to those employed in tracking and communicating with satellites and space probes. They may be used individually or linked together electronically in an array. Radio observatories are preferentially located far from major centers of population to avoid electromagnetic interference (EMI) from radio, television, radar, motor vehicles, and other man-made electronic devices.

Radio waves from space were first detected by engineer Karl Guthe Jansky in 1932 at Bell Telephone Laboratories in Holmdel, New Jersey using an antenna built to study radio receiver noise. The first purpose-built radio telescope was a 9-meter parabolic dish constructed by radio amateur Grote Reber in his back yard in Wheaton, Illinois in 1937. The sky survey he performed is often considered the beginning of the field of radio astronomy.