Somewhere in the cosmos an ordinary galaxy spins, seemingly at slumber. Then all of a sudden, WHAM! A flash of light explodes from the galaxy's center. A star orbiting too close to the event horizon of the galaxy's central supermassive black hole is torn apart by the force of gravity, heating up its gas and sending out a beacon to the far reaches of the universe.
In a universe with tens of billions of galaxies, how would we see it? What would such a beacon look like? How would we distinguish it from other bright, monumental intergalactic events, like supernovas?