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X-ray astronomy detectors are instruments that detect X-rays for use in the study of X-ray astronomy. X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray emission from celestial objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and satellites. X-ray astronomy is part of space science. ''X-ray astronomy detectors'' have been designed and configured primarily for energy and occasionally for wavelength detection using a variety of techniques usually limited to the technology of the time. ==Detection and imaging of X-rays== X-rays span 3 decades in wavelength (~8 nm - 8 pm), frequency (~50 PHz - 50 EHz) and energy (~0.12 - 120 keV). In terms of temperature, 1 eV = 11,604 K. Thus X-rays (0.12 to 120 keV) correspond to 1.39 × 106 to 1.39 × 109 K. From 10 to 0.1 nanometers (nm) (about 0.12 to 12 keV) they are classified as soft X-rays, and from 0.1 nm to 0.01 nm (about 12 to 120 keV) as hard X-rays. Closer to the visible range of the electromagnetic spectrum is the ultraviolet. The draft ISO standard on determining solar irradiances (ISO-DIS-21348) describes the ultraviolet as ranging from ~10 nm to ~400 nm. That portion closest to X-rays is often referred to as the "extreme ultraviolet" (EUV or XUV). When an EUV photon is absorbed, photoelectrons and secondary electrons are generated by ionization, much like what happens when X-rays or electron beams are absorbed by matter. The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes had a longer wavelength than the radiation emitted by radioactive nuclei (gamma rays). So older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10−11 m, defined as gamma rays. However, as shorter wavelength continuous spectrum "X-ray" sources such as linear accelerators and longer wavelength "gamma ray" emitters were discovered, the wavelength bands largely overlapped. The two types of radiation are now usually distinguished by their origin: X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus.〔 Although the more energetic X-rays, photons with an energy greater than 30 keV (4,800 aJ), can penetrate the air at least for distances of a few meters, the Earth's atmosphere is thick enough that virtually none are able to penetrate from outer space all the way to the Earth's surface (they would have been detected and medical X-ray machines would not work if this was not the case). X-rays in the 0.5 to 5 keV (80 to 800 aJ) range, where most celestial sources give off the bulk of their energy, can be stopped by a few sheets of paper; 90% of the photons in a beam of 3 keV (480 aJ) X-rays are absorbed by traveling through just 10 cm of air. To detect X-rays from the sky, X-ray detectors must be flown above most of the Earth's atmosphere. There are three main methods of doing so: sounding rocket flights, balloons, and satellites. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「X-ray astronomy detector」の詳細全文を読む スポンサード リンク
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