109384
Gamma rays from the decay of titanium-44 ( half-life about 60 years ) were independently discovered emanating from it , showing that it must have exploded fairly recently ( perhaps around the year 1200 ) , but there is no historical record of it .
 half-life
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:
 half-life