People are used to the stunning visual images taken by telescopes like the Hubble or the great telescopes in Hawaii or Chile, but maybe only have heard of radio astronomy through movies like “Contact.”
Since the 1930s, when the first radio signals from space were detected by Karl Jansky, astronomers have used radio telescopes to explore the Universe by detecting radio waves emitted by a wide range of objects. Our Sun, the nearest star to Earth is a powerful radio emission source, mainly due to its proximity to our planet, but some radio sources, which are millions, even billions of light years away, are truly colossal in terms of their radio output.
Radio astronomy progressed through the middle of the last century, with many great discoveries made in radio frequencies such as the discovery of pulsars by Dame Jocelyn Bell Burnell, a postgraduate student working at the University of Cambridge whilst a student under Anthony Hewish, who went on to share the Nobel Prize for Physics with Martin Ryle, another notable radio astronomer in part for this discovery.
Radio telescopes provide alternative views to optical telescopes, they can detect invisible gas, and can reveal areas of space that may be obscured with cosmic dust. Unlike optical telescopes, which can be hampered by cloud or poor weather conditions on Earth, radio telescopes, working with signals at a longer wavelength, can be used even in cloudy skies.
The longer wavelength of radio emissions means that the radio telescopes used to detect them do not have to be as perfectly shaped as their optical counterparts, (but still need to be accurate to around 1 mm in terms of accuracy of the dish shape) but, to obtain the same level of detail and resolution as their optical cousins, radio telescopes have to be much larger or have a much larger collecting area, as light is a much shorter wavelength. The largest radio telescope in the world as a single dish, is the Arecibo telescope, which featured in the movie “Contact”, and is located in a natural hollow in Puerto Rico, South America. (Courtesy: https://skatelescope.org/radio-astronomy/)