A Doppler Effect for Distant Planets

Published in Science, 1 Aug 2013

An ambulance whizzes by, and suddenly its siren drops in pitch. We are all familiar with the Doppler effect, even if we don’t know it by name. Now, scientists have found an alternative version of the phenomenon, for when sound, or light, scatters off a rotating object. The discovery could enable astronomers to measure a distant planet’s rotation, or even improve the performance of wind turbines.

Here’s how the Doppler effect works: When a noisy object is moving toward you, its sound waves bunch up, producing a higher frequency, or pitch. Conversely, as soon as the object is moving away from you, the sound waves stretch out, and the pitch lowers. The faster the object, the greater the pitch change. […]

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