An Ellerman bomb is a small, bright structure, also known as a Severny moustache, that appears in a solar active region, most often in an emerging flux region or on the edge of a sunspot where the magnetic field is breaking through the surface. Ellerman bombs usually last less than 5 minutes and are best seen it the wings of H-alpha; they are named after the American astronomer Ferdinand Ellerman (1869–1940).