Glossary term: X-ray Astronomy

Description: X-ray astronomy is a field of study dedicated to collecting and analyzing all the information that comes from the cosmos in very energetic electromagnetic radiation (more energetic than ultraviolet radiation but less energetic than gamma radiation). X-rays have frequencies between 30 petahertz and 30 exahertz, which corresponds to wavelengths between 10 picometers and 10 nanometers. In the older unit of length still in use in many areas of astronomy, including X-ray astronomy, this corresponds to between 0.1 and 100 angstroms (Å). Given the prominence of the particle nature of light in that part of the spectrum, X-ray astronomers commonly use photon energies instead of wavelength to characterize what they measure. In terms of electron volts (eV), the energy measure common in particle physics, the above frequency and wavelength ranges correspond to photon energies between 100 eV and 100 keV. As the atmosphere absorbs most X-rays, X-ray astronomy is typically done by space telescopes. X-rays from astronomical sources come from extremely hot regions. These include the disks around compact objects such as black holes or neutron stars, and the hot corona of stars.

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