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Both astrometry and radial velocity use cyclical variations of a star’s speed caused by a planet’s gravitational force to detect exoplanets. The radial velocity method measures changes in the star’s radial velocity relative to the Earth. These changes will cause the star to blueshift or redshift as it moves towards or away from the Earth due to the Doppler effect. Extrasolar planets discovered by way of radial velocity are planets that are higher in mass and temperature and closer to their parent stars. This type of planet is known as a hot Jupiter.

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