|the branch of astronomy concerned with the detection and measurement of X-rays emitted by certain celestial bodies. As X-rays are absorbed by the atmosphere, satellites and rockets are used|
|an extraordinary or unusual thing, person, or event; an exceptional example or instance.|
|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
The study of celestial objects by measurement of the x-rays they emit. Because the Earth's atmosphere absorbs x-rays, x-ray detectors are usually carried into space on satellites. X-rays are emitted by high-energy objects such as active galactic nuclei, supernova remnants, x-ray binary stars, neutron stars, and the regions around black holes. Objects which do not produce their own x-rays can reflect radiation from nearby stars, making it possible to study the objects using x-ray astronomy; one notable example of this is the analysis of solar x-rays reflected by the Moon.