The M–Sigma Relation: How Supermassive Black Holes Shape Their Galaxies

The M–sigma relation is a powerful empirical law in astrophysics linking the mass of a supermassive black hole to the velocity dispersion of stars in its host galaxy's bulge. Discovered in 2000, this tight correlation revealed that black holes are not just passive objects but fundamental components that co-evolve with their galaxies. This article explores its discovery, the physics behind it, and why it revolutionized our understanding of the universe.