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Alan Stern has argued that location should not matter and that only geophysical attributes should be taken into account in the definition of a planet , and proposes the term " satellite planet " for a planet-sized satellite .
 Alan Stern
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Alan Stern