Dozens of tiny galaxies known as satellite galaxies orbit the Milky Way, but theorists predict there should be hundreds. Now a team of astronomers offers a new resolution to this conflict between observation and theory: Maybe dark matter, the mysterious substance thought to bind galaxies together, isn’t quite so dark. The researchers propose that radiation might have stirred up dark matter in the early universe, preventing the formation of satellites.
The mystery of the missing satellite galaxies has bedeviled astronomers for more than a decade. While dark matter has proven to be exceptionally good at explaining the formation of large galaxies and clusters, it routinely runs into trouble when attempting to describe tiny structures such as satellite galaxies.
