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 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 heat would keep that region from cooling further -- an effect known as conduction.
"It would be like putting an ice cube in a boiling pot of water -- the average temperature is pretty much still boiling," says Michael McDonald, a Hubble Fellow in MIT's Kavli Institute for Astrophysics and Space Research. "At super-high temperatures, conduction smooths out the temperature distribution so you don't get any of these cold clouds that should form stars."
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