Astronomy question?

Question

Looking through historical records of the quasar 3C49, which is at a distance of 150 Mpc, you discover that it underwent a brightening beginning in 1959 and lasting for 11 years before fading back to its original brightness. At its maximum brightness, it was 70 times brighter than it is normally.

What is the largest possible size of the region that underwent the outburst? Express your answer in light years:

Answer 1

Sounds like a homework question to me, given that, "Express your answer in light years" part.

OK, the answer would probably be 11 light years or less for the size of the region that underwent the outburst. Or maybe 22 light years if it started in the middle and spread outward from there in all directions. This is because nothing can travel faster than light, not even a blast from from an explosion.

Answer 2

Hi. Assuming that the quasar had previously blown off gas that would be illuminated by the quasar, the DIAMETER of the gas field and light reflecting from it could be just under 8 light years. The front of the field would brighten from light heading in our direction and the light reflecting from the far side would start to show reflected light about 12 years later, but dimmer. If the light was due SOLELY to the quasar then the time would be a function of how long the brightening lasted. The question was "maximum". My guess is about 8 light years.

Answer 3

Hmm...I can't quite see how brightness of an object at that distance can be directly correlated to an area (size of a region)...?
We see quasars, which are most likely just ancient galaxies, as nothing more than points of light anyway -- no area measurements.
I suppose you might be able to figure an average size for a galaxy in our universe, and from its distance get its extent in arc-seconds from that, and use that as the answer...but that doesn't quite seem right to me. Hmm...?

Answer 4

Huh!?