A Tour of the Phoenix Cluster

Narrator (April Jubett, CXC): Astronomers have confirmed the first example of a supermassive black hole unable to prevent copious numbers of stars forming in the core of galaxy cluster where it resides. This result provides new details about the life cycles of some of the most extreme objects in the universe.

Galaxy clusters are the largest structures in the cosmos that are held together by gravity, and consist of hundreds or even thousands of galaxies embedded in hot gas, and invisible dark matter. The largest supermassive black holes astronomers have ever found are in the centers of galaxy clusters.

For decades, astronomers thought galaxy clusters should contain rich nurseries of stars in their centers, resulting from cooling of their huge reservoirs of hot gas. Instead, they found the powerful, giant black holes were pumping out energy via jets and keeping the gas too warm to form many stars.

Now, scientists have compelling evidence that stars are forming at a furious rate in the Phoenix galaxy cluster, apparently linked to a less effective black hole in its center. In this unique cluster, outbursts from the central black hole instead appear to be aiding in the formation of stars. They used new data from NASA's Chandra X-ray Observatory and Hubble Space Telescope, and the NSF's Karl Jansky Very Large Array, or VLA, to build on previous observations of this cluster.

Data from Chandra show that the coolest gas it can detect is located near the center of the cluster. In the absence of significant sources of heat, astronomers expect cooling to occur at the highest rates in a cluster's center, where the densest gas is located.Outbursts powered by the black hole then forced the gas to cool even more quickly. The outbursts drove a pair of jets seen in radio waves by the VLA, which pushed outward and inflated cavities in the hot gas, detected with Chandra. Filaments of cool gas observed by Hubble are located around the borders of the cavities, so the authors concluded that the black hole's outburst carried the gas away from the black hole. The farther away from the black hole, the faster the gas can cool to form stars.

This latest result on the Phoenix Cluster demonstrates that the supermassive black holes at the centers of galaxy clusters can have dramatic — and different — impacts on their surroundings. Astronomers will continue to use Chandra and other telescopes to learn more about the Phoenix Cluster and other cosmic giants like it.