Radio Telescope

Radio telescope

An instrument used to detect radio emissions from the sky, whether from natural celestial objects or from artificial satellites.
A radio telescope is a specialized antennaand radio receiver used to receive radio waves from astronomical radio sources in the sky in radio astronomy. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of theelectromagnetic 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. 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 singly, or linked together electronically in an array. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night. Since astronomical radio sources such as 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 observatories are preferentially located far from major centers of population to avoid electromagnetic interference (EMI) from radio, television, radar, motor vehicles, and other EMI emitting 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 noise in radio receivers. 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 did with it is often considered the beginning of the field of radio astronomy.
                                          https://en.wikipedia.org/wiki/Radio_telescope

History

Early radio telescopes

Full-size replica of the first radio telescope, Jansky's dipole array, preserved at the US National Radio Astronomy Observatory in Green Bank, West Virginia.

The first radio antenna used to identify an astronomical radio source was one built by Karl Guthe Jansky, an engineer with Bell Telephone Laboratories, in 1932. Jansky was assigned the job of identifying sources of static that might interfere with radio telephone service. Jansky's antenna was an array of dipoles and reflectors designed to receive short wave radio signals at a frequency of 20.5 MHz (wavelength about 14.6 meters). It was mounted on a turntable that allowed it to rotate in any direction, earning it the name "Jansky's merry-go-round". It had a diameter of approximately 100 ft (30 m) and stood 20 ft (6 m) tall. By rotating the antenna, the direction of the received interfering radio source (static) could be pinpointed. A small shed to the side of the antenna housed an analog pen-and-paper recording system. After recording signals from all directions for several months, Jansky eventually categorized them into three types of static: nearby thunderstorms, distant thunderstorms, and a faint steady hiss of unknown origin. Jansky finally determined that the "faint hiss" repeated on a cycle of 23 hours and 56 minutes. This period is the length of an astronomical sidereal day, the time it takes any "fixed" object located on the celestial sphere to come back to the same location in the sky. Thus Jansky suspected that the hiss originated outside of the Solar System, and by comparing his observations with optical astronomical maps, Jansky concluded that the radiation was coming from the Milky Way Galaxy and was strongest in the direction of the center of the galaxy, in the constellation of Sagittarius.

Reber's first "dish" radio telescope - Wheaton, IL 1937

An amateur radio operator, Grote Reber, was one of the pioneers of what became known as radio astronomy. He built the first parabolic "dish" radio telescope, a 9 metres (30 ft) in diameter) in his back yard in Wheaton, Illinois in 1937. He repeated Jansky's pioneering work, identifying the Milky Way as the first off-world radio source, and he went on to conduct the first sky survey at very high radio frequencies, discovering other radio sources. The rapid development of radar during World War II created technology which was applied to radio astronomy after the war, and radio astronomy became a branch of astronomy, with universities and research institutes constructing large radio telescopes.

Benefits

Advantages of radio telescopes. Radio waves are not blocked by clouds and are unaffected by the Earth's atmosphere, thus radio telescopes can receive signals during cloud cover. The exception being strong winds which affect the large dish and thunderstorms due to interference.

Own Opinion

             radio telescope is useful in our world 

because it give signal to our world