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Gas-poor disks of circumstellar dust have been found around many nearby stars - most of which have ages in the range of ~ 10 million years ( e.g. Beta Pictoris , 51 Ophiuchi ) to billions of years ( e.g. Tau Ceti ) .
 Beta Pictoris, 51 Ophiuchi, Tau Ceti
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:
 Beta Pictoris, 51 Ophiuchi, Tau Ceti