<![CDATA[ "It is fascinating that an active galactic nucleus can change its brightness so dramatically over such a short period of time." ]]>
An active galactic nucleus (AGN) is a region at the center of a galaxy that is extremely bright and energetic, often due to the presence of a supermassive black hole that is actively accreting material. AGNs can vary dramatically in brightness over short periods, indicating complex physical processes at play.