|Messier 51 with supernova SN2011dh. Companion galaxy NGC 5195 at bottom.|
In fact, when this supernova first exploded, it was emitting as much energy individually as the rest of the hundreds of billions stars in M51 combined. The reasons it doesn't appear as bright as the rest of the galaxy are 1) it was about five days old by the time I took this picture, so it had begun to fade a little. And 2) most of that energy is not in the visible portion of the spectrum. Remind me sometime when it's not so late to explain the details behind a supernova type IIa.
As an aside, you can't see them in this picture because of the exposure settings I chose, but I caught two extremely faint satellite trails in my exposures, one of which neatly passed diagonally from lower-left to upper-right between M51 and the star on the right.