Sun, optical image in hydrogen alpha light. Hydrogen alpha (Ha) is a wavelength of light at which hydrogen absorbs and emits light. It has a wavelength of 656.3 nanometres, which is detected as red by the eye. Excluding all other wavelengths allows fine detail to be seen on the Sun. The visible surface (photosphere) comprises cells made up of areas of rising (hot) and falling (cooler) material. These are constantly shifting and writhing on the surface. Dark prominences and bright sunspots are also seen.