In 1953 Iosif Shklovsky proposed that the diffuse blue region is predominantly produced by synchrotron radiation, which is radiation given off by the curving of electrons moving at speeds up to half the speed of light.
The diffuse blue region is predominantly produced by synchrotron radiation. This was what Iosif Shklovsky proposed in 1953. Synchrotron radiation is radiation. This radiation is given off by the curving of electrons. These electrons are moving at speeds up to half the speed of light.