Summary of the past, present and future of the X-ray astronomy

The first cosmic X-ray source Sco X-1 was discovered with an Aerobee rocket in 1962 by Riccardo Giacconi. Since then, the field of X-ray astronomy developed significantly, not only in terms of capabilities and technology of X-ray observatories, but also in terms of theoretical understanding of a very wide range of astronomical objects and fields. The X-ray astronomy usually refers to the energy range of fractions of keV to a few hundred keVs, and creation of these photons in large amounts requires extremely high temperatures, magnetic fields, and extreme environments. This review summarizes the historical development of X-ray astronomy, provides introductory information regarding X-ray detectors and telescopes, discusses the current operational X-ray observatories, and finally introduces a sample of upcoming X-ray observatories that will revolutionize the field in the near future.