BBC: Astronomers have now seen evidence that the central galaxy in a huge galaxy cluster is making new stars at a surprisingly vigorous rate. From their observations using 10 different telescopes worldwide, the researchers estimate that the galaxy, located in the Phoenix cluster—formally known as SPT-CLJ2344-4243—is making about 740 stars a year. Galaxy clusters—the largest gravitationally bound structures in the universe—typically consist of hundreds of galaxies orbiting their mutual center of mass. In most clusters, the large galaxies closest to the center are believed to have a central black hole surrounded by a lot of gas. While the black hole’s gravity draws material in, the black hole itself releases huge amounts of energy that heats the gas, resulting in what has been described as a tug of war. If, however, the gas gets a chance to cool down, it can draw together and start forming stars. The astronomers surmise that the black hole at the core of the Phoenix cluster’s central galaxy must not be releasing as much energy, because they have detected particularly bright emissions in the UV range, indicating potentially hundreds of young stars.