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The natural satellites orbiting relatively close to the planet on prograde , uninclined circular orbits ( " regular " satellites ) are generally thought to have been formed out of the same collapsing region of the protoplanetary disk that created its primary .
 " regular " satellites
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:
 " regular " satellites