Astronomy
Quasars as Active Galactic Nuclei
Quick fact
A single quasar can outshine an entire galaxy of a hundred billion stars, yet its entire energy output comes from a region no larger than our solar system.
Why this is interesting
Looking at the night sky, the brightest stars are often close by. But what if the most brilliant objects in the universe turned out to be the cores of distant galaxies—each powered by a black hole?