Black holes are known to exist at the centres of most galaxies, including our own Milky Way. The masses of those black holes are correlated to many of the properties of their host galaxies, which strongly suggests that galaxies and black holes evolve together. Measuring their masses Continue reading How to Weigh a Supermassive Black Hole?
Early astronomers already make the distinction between stars and planets, as the former remain relatively fixed for centuries, while the latter wander an appreciable amount in a comparatively short time. But that’s not all!