Telescopes
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"Radio telescopes." Technology, Telescopes, Q-files Encyclopedia, 13 Mar. 2026.
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Accessed 13 Sep. 2026.
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Technology, Telescopes, s.v. "Radio telescopes," accessed September 13, 2026.
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Radio telescopes
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.
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.
Arrays of telescopes
A way of increasing the resolution (sharpness) of the image received is to use more than one radio telescope linked together. The signals are then combined to form a single image. The array of telescopes is called an astronomical radio interferometer. All of the telescopes in the array are widely separated—sometimes spread over entire continents—but are connected by cable or optical fibre links.
Square Kilometre Array
The world’s largest and most powerful radio astronomy observatory, the Square Kilometre Array (SKA), is under construction in Western Australia. The SKA will initially involve two telescope arrays. One is called SKA-Low, so named for its sensitivity to low-frequency radio signals. Consisting of 131,072 Christmas tree-like antennas, it is located at Inyarrimanha Ilgari Bundara (a place name that means "sharing sky and stars"), and forms the CSIRO Murchison Radio-astronomy Observatory on Wajarri Yamaji Country, Western Australia.
A second array of 197 traditional dishes, SKA-Mid, which will observe at mid-frequencies, is to be built in South Africa’s Karoo region. SKA-Mid's baseline (the largest distance between any two of its dishes) is 150 kilometres (93 miles), giving it high resolving power, enabling it to detect much finer details in radio-emitting objects than other radio telescopes.
The large collecting area of both arrays is what makes the SKA so powerful, enabling it detect extremely faint objects. Both SKA-Mid and SKA-Low are interferometers (see above). They use a technique called aperture synthesis, in which multiple telescopes in different locations are connected—by fibre-optic cables—in such a way to act as one. When the SKA begins operations in 2028–29, the maps of the radio sky it creates will help astronomers study the evolution of galaxies, the location of dark matter and how the strength of dark energy has grown over time.
Consultant: Chris Oxlade
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