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Radio astronomy uses radio waves to study regions of space.
Radio waves are a form of electromagnetic radiation - like visible light waves only with much longer wavelengths. Visible light waves are oscillating electromagnetic signals with wavelengths of less than one millionth of a metre, whereas radio waves have wavelengths in the range of a few millimetres to several metres. Radio telescopes gather and concentrate the radio waves from an astronomical source. The signal received is then electronically processed so that it can be measured by a computer. When a picture of an area of the sky is to be built up the signals are stored in a computer and displayed as a radio-wave intensity map of the region being observed.