Just as optical telescopes collect visible light, bring it to a focus, amplify it and make it available for analysis by various instruments, so do radio telescopes collect weak radio light waves, bring it to a focus, amplify it and make it available for analysis. We use radio telescopes to study naturally occurring radio light from stars, galaxies, black holes, and other astronomical objects. We can also use them to transmit and reflect radio light off of planetary bodies in our solar system. These specially-designed telescopes observe the longest wavelengths of light, ranging from 1 millimeter to over 10 meters long. For comparison, visible light waves are only a few hundred nanometers long, and a nanometer is only 1/10,000th the thickness of a piece of paper! In fact, we don’t usually refer to radio light by its wavelength, but by its frequency.
Naturally occurring radio waves are extremely weak by the time they reach us from space. A cell phone signal is a billion billion times more powerful than the cosmic waves our telescopes detect.
A radio telescope is a form of radio receiver used in astronomy.
In contrast to an "ordinary" telescope, which receives visible light, a radio telescope "sees" radio waves emitted by radio sources, typically by means of a large parabolic ("dish") antenna, or arrays of them.
Many celestial objects, such as pulsars or active galaxies (like quasars), produce radio-frequency radiation and so are best "visible" or even only visible in the radio region of electromagnetic spectrum.
By examining the frequency, power and timing of radio emissions from these objects, astronomers can improve our understanding of the Universe.
Radio telescopes are also the primary means to track space probes, and are used in the SETI project.
We use radio telescopes to study naturally occurring radio light from stars, galaxies, black holes, and other astronomical objects. We can also use them to transmit and reflect radio light off of planetary bodies in our solar system
