76040
It was discovered by William Denning in 1886 and was discovered to be the source of rare fireballs by Alexander Stewart Herschel .
 William Denning, Alexander Stewart Herschel
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:
 William Denning, Alexander Stewart Herschel