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Radio telescopes

A radio telescope image of a distant galaxyA radio telescope image of a distant galaxy Objects in space, such as stars and galaxies, do not just give off light. They also give off radiation from other parts of the electromagnetic spectrum, such as infrared radiation, radio waves, X-rays and ultraviolet radiation. There are some objects in space that only give off these kinds of radiation and that are otherwise invisible. They cannot be seen with ordinary optical telescopes, so special telescopes, called radio telescopes, are needed.

The Crab Nebula seen through different telescopesThe Crab Nebula seen through different telescopes

The Arecibo radio telescope in Puerto RicoThe Arecibo radio telescope in Puerto Rico


Radio telescopes look like giant satellite dishes. The dish acts as a reflector, collecting radio waves and focusing them on to a detector, where an image is formed. They can be turned to face any part of the sky. They are also used in the search for alien life in the Universe. Radio astronomy has led to the discovery of new celestial objects such as pulsars, rapidly spinning neutron stars.

The largest radio telescope is the RATAN-600 array near Nizhny Arkhyz, Russia. It consists of a 576 m (1890 ft) circle of dishes. The second largest is the Five-hundred-metre Aperture Spherical radio Telescope (FAST) in Guizhou, which began operations in September 2016.

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