1. The problem statement, all variables and given/known data Quasars have a luminosity on the order of 10^12 times more than our Sun. Our Sun is expected to last 5 billion years. Using this number estimate (in seconds) how long our Sun would last if it started using energy at the rate of a Quasar. 2. Relevant equations None 3. The attempt at a solution From the information given, there is no equation given so I did some research and it looks like you can roughly approximate that the luminosity of a star is inversely proportional to its lifetime therefore I did the following: 5 billion years = 1.58 x 10^17 seconds I then simply divided this by 10^12 to give - 158,000 s or 44 hours Does this sound right? Also, is it acceptable to approximate the age of a star to being inversely proportional to its luminosity. I see no other way of doing it based on the information given. Thanks.