High-energy electromagnetic radiation, with short wavelength (~10-0.01 nm) and high frequency (greater than
~1016 Hertz). Although the boundaries are somewhat arbitrary, wavelengths shorter than 0.01 nm are called gamma-rays and those longer than 10 nm extreme ultraviolet (EUV). X-rays would be produced by blackbody radiation at temperatures in excess of 106 K. Sources of astrophysical X-rays include accretion disks, gas impacting on neutron stars, X-ray bursters, and hot gas located in the centers of galaxy clusters.