Telescopes from the Ground Up
Two images of Saturn: One taken in visible light using the Hubble Space Telescope and one in radio wavelengths using the Very Large Array.

Radio waves have another advantage. Because their wavelengths are so long, they reach the ground undistorted by the atmosphere. Visible light, with its comparatively short wavelengths, is subject to atmospheric distortion — the unpredictable bending of light as it passes through warm and cool air pockets. Atmospheric distortion blurs visible light images.

Seeing the invisible

Many celestial objects, including some planets, comets, giant clouds of gas and dust, pulsars, and black holes, emit radio waves. Astronomers can learn about the composition, structure, and motion of these astronomical objects from the radio waves they emit. Scientists have also developed sophisticated systems that create images from these radio signals in order to “see” the objects in the radio light they emit.

To get a clear picture, radio telescopes have to be huge, because radio waves are so large. For example, a dish 64 meters wide produces an image that is about as detailed as a visible-light image from a small backyard telescope. To create clearer, higher-resolution radio images, several smaller telescopes or dishes are often combined to form an array. Together, the dishes act like a single telescope as large as the diameter of the array.

Click here to see all avaliable eras.