Very compact but bright objects called quasars, which can outshine a thousand normal galaxies, were abundant when the universe was less than 10 percent of its present age. Quasars are powered by black holes weighing more than a billion suns. How did they get so big so fast?
The front-running theory
Co-evolution holds that galaxies and supermassive black holes evolve together, each counting on the other for its ultimate heft.
