International Ultraviolet Explorer was considered the most successful astronomical satellite ever. The human eye can perceive light with wavelengths between roughly 350 (violet) and 700 (red) nanometres. Ultraviolet light has wavelengths between roughly 10 nm and 350 nm. UV light can be harmful to human beings, and is strongly absorbed by the ozone layer. This makes it impossible to observe UV emission from astronomical objects from the ground. Many types of object emit copious quantities of UV radiation, though: the hottest and most massive stars in the universe can have surface temperatures high enough that the vast majority of their light is emitted
Radiation effects from the Fukushima Daiichi nuclear disaster to poison centres around the world after taking iodine tablets in response to fears about harmful levels of radiation coming out of the damaged nuclear power plant in Fukushima. In Operation Tomodachi, the United States Navy dispatched the aircraft carrier and other vessels in the Seventh Fleet to fly a series of helicopter operations. A U.S. military spokesperson said that low-level radiation forced a change of course en route to Sendai. The "Reagan" and sailors aboard were exposed to "a month's worth of natural background radiation from the sun, rocks or soil" in an hour and the carrier was repositioned.