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In 1928 , he studied Albrecht Unsöld 's hypothesis , and discovered that three quarters of the Sun is made of hydrogen , and about one quarter is helium , with 1 % being other elements .
 person: Albrecht Unsöld
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 person: Albrecht Unsöld