68968
By comparing the spectra of stars such as Sirius to the Sun , they found differences in the strength and number of their absorption lines - the dark lines in stellar spectra caused by the atmosphere 's absorption of specific frequencies .
 Sirius
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:
 Sirius