When most people try to picture a telescope, they probably imagine the long tube and tripod of an optical telescope. Optical telescopes work by gathering and focusing the visible light in the night sky which includes starlight, the light reflected off planets, and the faint light from deep sky objects such as nebulae. With optical telescopes, the larger its lens, the more light it can gather, and thus, produce a higher quality image. There are many other kinds of telescopes besides optical ones, but this general rule applies to all of them: bigger is always better.
With that in mind, the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) and Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) are working together to build the world’s largest single dish radio telescope – the Five hundred metre Aperture Spherical Telescope (FAST) (Chinese: 五百米口径球面射电望远镜) or Tianyan (Chinese: 天眼). Upon completion, FAST will be a whopping 200 meters larger than the world’s current largest radio telescope in Arecibo, Puerto Rico. Why build such a large dish? Because the larger the telescope’s dish, the more radio signals it can hear.
“A radio telescope is like a sensitive ear, listening to tell meaningful radio messages from white noise in the universe. It is like identifying the sound of cicadas in a thunderstorm,” said Nan Rendong, chief scientist of the FAST project.
Equipped with state of the art multi-beam and multi-band receivers developed by CISRO, FAST will be capable of searching two to three times more sky area than most radio telescopes. The telescope will look for ancient signals of neutral hydrogen in the Milky Way and other galaxies, which will help scientists to understand the origins and evolution of the cosmos.
The telescope sits within a valley in the Karst depression, an 800-meter wide natural basin located about 170 km by road from the provincial capital Guiyang, near the village of Dawodang, in the Guizhou Province of southwest China. The site provides major advantages for the telescope such as protection from the elements and complete isolation from human-caused interference. The site’s low latitude also allows for better views of southern galactic objects.
“A radio telescope is like a sensitive ear, listening to tell meaningful radio messages from white noise in the universe.”
The reflector dish is made of about 4,500 adjusting triangular panels, which will curve in relation to the segment of sky being surveyed. As the radio signals are reflected, they will be transmitted to the receiver.