The Sun in various wavelengths of ultraviolet radiation In the visible range, the Sun looks quite calm, with few dark spots. But radiation in various wavelengths of ultraviolet radiation reveals much more detail: we can see bright prominences at the edge of the solar disk; loops of matter above the spots, stretching along the magnetic field lines. All of these observations are made by the Solar Dynamics Observatory (SDO). Much of this is invisible from Earth, since the atmosphere blocks a signif