The book in a popular form acquaints the reader with the modern state of X-ray astrophysics, with studies of the Universe in a rigid energy range. Having arisen only twenty years ago, this area of ​ ​ astrophysics is developing very rapidly, replete with numerous discoveries. The book tells about the research of X-ray sources in binary systems, about the X-ray radiation of the remnants of supernova flares, about X-ray flashes, etc. The reader will get an idea of ​ ​ the physical nature of objects that are X-ray sources, the nature of their radiation, the connection of X-ray astrophysics with other sections of astrophysical science. For readers with secondary education, students, teachers and a wide range of people interested in the current problems of modern astrophysics.