Ask Ethan: How Many Black Holes Are There In The Universe?
For the third time in history, we've directly detected an unmistakable signature of black holes: gravitational waves resulting from their merger. Combine that with what we know from stellar orbits around the galactic center, X-ray and radio observations of other galaxies, and gas infall/velocity …
John Catanzaro flipped this story into AstroPics•2480d