Planets, comets, stars, and galaxies all generate or reflect electromagnetic energy at many different wavelengths. Some of the energy they emit is in the form of very large wavelengths called radio waves.
Devices used to detect radio waves from objects in space are called radio telescopes. Radio telescopes are large dishes made out of metal that reflect radio waves to a central point called an antenna. The picture to the right shows a typical radio telescope.
Just as with optical telescopes, the larger the radio telescope is, the more radio waves it can collect. Astronomers combine several small telescopes into a group or an array. This combination of telescopes gives better and clearer images. An array of radio telescopes is pictured below.
By studying the radio waves from planets, stars, and galaxies, astronomers can learn about their composition, structure, and motion. Radio astronomy has the advantage that sunlight, clouds, and rain do not affect observations.
Watch this video to learn more about radio telescopes.