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• n  change in the apparent frequency of a wave as observer and source move toward or away from each other

• Doppler effect
• Doppler shift

News & Articles

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• Astronomers Determine the Length of Day of an Exoplanet
  The Bad Astronomer writes: "Astronomers have just announced that the exoplanet Beta Pic b — a 10-Jupiter-mass world 60 light years away — rotates in about 8 hours. Using a high-resolution spectrometer and exploiting the Doppler shift of light seen as the planet spins, they measured its rotation velocity as 28,000 mph. Making reasonable assumptions about the planet's size, that gives the length ...
  April 30, 2014 - Slashdot