Why isn’t the universe as bright as it should be?
A handful of new stars are born each year in the Milky Way, while many more blink on across the universe. But astronomers have observed that galaxies should be churning out millions more stars, based on the amount of interstellar gas available. Now researchers from MIT, Columbia University, and Michigan State University have pieced together a theory describing how clusters of galaxies may regulate star formation. They describe their framework this week in the journal Nature. When intracluster gas cools rapidly, it condenses, then collapses to form new stars. Scientists have long thought that something must be keeping the gas from cooling enough to generate more stars — but exactly what has remained a mystery. For some galaxy clusters, the researchers say, the intracluster gas may simply be too hot — on the order of hundreds of millions of degrees Celsius. Even if one region experiences some cooling, the intensity of the surrounding...