Active galactic nuclei.

Fabian, A C · Proc Natl Acad Sci U S A · 1999

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Abstract

Active galactic nuclei are the most powerful, long-lived objects in the Universe. Recent data confirm the theoretical idea that the power source is accretion into a massive black hole. The common occurrence of obscuration and outflows probably means that the contribution of active galactic nuclei to the power density of the Universe has been generally underestimated.