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Radio telescopes

This photo of a galaxy in the constellation of Hercules was produced from combining an optical image from the Hubble Space...Read More >>This photo of a galaxy in the constellation of Hercules was produced from combining an optical image from the Hubble Space telescope and a radio image from the Very Large Array (VLA) telescope in New Mexico, USA. The VLA radio telescope reveals two spectacular pink jets of energetic particles blasting out of a black hole at the centre of the Hercules galaxy (the yellowish cloud) that would be otherwise invisible. 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 same object, the Crab nebula, seen through three different telescopes which detect different forms of radiation


The Arecibo radio telescope in Puerto Rico. The dish is built into a natural bowl in the landscape. It focuses radio waves from...Read More >>The Arecibo radio telescope in Puerto Rico. The dish is built into a natural bowl in the landscape. It focuses radio waves from the sky on the dome suspended above it on cables. The telescope is used in the search for extraterrestrial life. A signal intended for possible aliens, called the Arecibo message, was transmitted towards a cluster of stars about 25,000 light-years away in 1974.

Dishes

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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