The active galactic nucleus NGC 4151 (IMAGE) University of Michigan Caption An artist's rendering of what's called an active galactic nucleus at the center of NGC 4151. The galaxy's black hole sits at the center, immediately surrounded by an accretion disk shown in blue. Credit JAXA Usage Restrictions No restrictions License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.