Astronomers discover black hole in Earth's galactic backyard

[kurtcagle]

8. Yup.

Gamma radiation is light from the extreme edge of the electromagnetic spectrum with frequencies in the exaHertz range. (10^18 and above). So you're right - you likely wouldn't see such a blast coming, though it's possible that you might pick up the gravity waves of two black holes circling one another for months before that event happened, and might actually see the leadup visually to such a blast if it was within a thousand lightyears or so. Also keep in mind that if it WAS in the galactic plane, you'd likely see the effect of the tightening magnetic stream on intervening gas clouds.