Colossal bubbles containing magnetic fields may comprise a key force at work in galaxy clustersthe building blocks of the universeaccording to new research. Astronomers have known for some time that magnetic fields exist in deep space, and that they most likely play an important role in galaxy cluster formation. Yet the origin of these fields has proved elusive. Now observations of so-called ghost cavities in the clusters suggest that these bubbles may be the source.

Aided by the Chandra X-ray Observatory, Brian McNamara of Ohio University and colleagues found Milky Way-size cavities in galaxy cluster Abell 2597 (see image). Their data, McNamara reported yesterday at a meeting of the Astronomical Society in Washington, D.C., suggest that such cavities contain magnetic fields that they ferry out from the centers of clusters, much like soft-drink bubbles rising to the surface. When the bubbles burst, the magnetic fields are released into the cosmos.

This kind of activity may have influenced the evolution of the early universe. "We think magnetism, in some locations of the universe, could have been as important as gravity in shaping the overall structure," MacNamara asserts. It may also impact stellar evolution in today's galaxies. The team notes that as a bubble migrates out, the gases in its path cool and the matter condenses, falling into a black hole at the galaxy cluster's center. An explosion of radio emission follows, distributing potentially star-forming matter through the cluster.