The Largest Black Holes in the Universe

Our Milky Way may harbor millions of black holes... the ultra dense remnants of dead stars. But now, in the universe far beyond our galaxy, there’s evidence of something far more ominous. A breed of black holes that has reached incomprehensible size and destructive power. Just how large, and violent, and strange can they get? A new era in astronomy has revealed a universe long hidden to us. High-tech instruments sent into space have been tuned to sense high-energy forms of light -- x-rays and gamma rays --