extreme ultraviolet

Extreme ultraviolet (EUV or XUV) is the shortest-wavelength ultraviolet (UV) radiation, adjacent to X-ray and at the far end of the UV spectrum from visible light. A typical cited wavelength-range is 10-124 nm (ultraviolet's full range is 10-400 nm). EUV is completely absorbed by Earth atmosphere and its astronomical observation is carried out by space observatories. Observation is used to study the corona of the Sun (revealing the Sun's magnetic topology) and to study the interstellar medium (ISM). It is ionizing radiation, capable of significant photoionization, a significant factor in some astrophysical processes, and a quality that makes it a danger both to humans and to spacecraft.