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Astronomers at the Observatory of Geneva were then able to use characteristic red shift s and blue shift s in the host star 's spectrum as its radial velocity varied over the course of the planet 's orbit to measure the planet 's mass and obtain an indication of its orbital eccentricity .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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