A Tour of NGC 4696

Narrator (April Hobart, CXC): The Centaurus Cluster is a collection of hundreds of galaxies located about 145 million light years from Earth. At the center of the cluster is a large elliptical galaxy called NGC 4696. Buried within the core of NGC 4696 lies a supermassive black hole.

Astronomers have been studying the Centaurus Cluster using several different telescopes to learn more about this system. Data from the Chandra X-ray Observatory, the Very Large Array, and the Hubble Space Telescope have revealed evidence for multiple outbursts, or eruptions, from the black hole in NGC 4696 that date back millions of years. When these eruptions happen, they send energy and particles outward, affecting things like the chemical composition of the interstellar material as well as the rate of star formation.

By employing a special type of processing of the X-ray data, the astronomers also discovered a sequence of curved features, approximately equally spaced, in the hot gas detected by Chandra. These arcs may be caused by sound waves generated by the black hole's repeated bursts. In a galaxy cluster, the hot gas that fills the cluster enables sound waves — albeit at frequencies far too low for the human hear to detect — to propagate.

Researchers will continue to study the Centaurus Cluster and others like it to learn more about how galaxy clusters and the black holes within them grow and evolve over time.