Electromagnetic radiation of the same nature as visible light, but having a wavelength approximately one thousandth that of visible light.
Synonyms: X ray · X-radiation · X-ray · X-raying · roentgen ray
Detection of X-rays from intensely hot gas in the universe. Such X-rays are prevented from reaching the Earth's surface by the atmosphere, so detectors must be placed in rockets and satellites. The first celestial X-ray source, Scorpius X-1, was discovered by a rocket flight 1962.
Since 1970, special satellites have been orbited to study X-rays from the Sun, stars, and galaxies. Many X-ray sources are believed to be gas falling on to neutron stars and black holes.