Gamma-quanta in the Universe

For a very long time, astronomy was a purely "optical" science. Perhaps even more promising source of space information are gamma quanta in the Universe. The fact is that the energy of gamma quanta can be hundreds of thousands and millions times greater than the energy of photons of visible light. For such gamma quanta, Universe is virtually transparent. They propagate almost rectilinearly, they come to us from very distant objects and can provide extremely valuable information about many physical processes taking place in space. Especially important information gamma quanta in the universe are able to bring about unusual, extreme states of matter. For example, gamma quanta arise in the interaction substances and antimatter, as well as where cosmic rays are born - high-energy particle fluxes. The main difficulty of gamma observations in the universe is that although the energy of cosmic gamma quanta is very high, the number of these quanta in near-Earth space is negligible.

For a very long time, astronomy was a purely optical science. Perhaps even more promising source of space information are gamma quanta in the Universe

Modern gamma telescopes, even from the brightest gamma sources, register about one quantum in a few minutes. Significant difficulties also arise from the fact that the primary cosmic radiation has to be studied against a background of numerous disturbances. Under the action of charged particles of cosmic rays coming to Earth, protons and electrons, both the terrestrial atmosphere and the design of the spacecraft on which the recording equipment is mounted brightly "glow" in the gamma range.

How does the universe look in gamma quanta? Imagine for a moment that your eyes are sensitive not to visible light, but to gamma quanta. What picture would be presented to us? Looking at the sky, we would not see either the Sun or the usual constellations, and Milky Way would look like a narrow glowing strip.

At present, using the gamma-ray telescopes installed on space vehicles, several dozen sources of gamma quanta in the Universe have been registered. It is still impossible to say exactly what they are, whether they are stars or other compact objects, or, perhaps, extended formations. There is reason to believe that gamma quanta in the universe occur in nonstationary, explosive phenomena. Such phenomena include, for example, outbreaks of super new star. However, when examining 88 known supernova remnants, only two gamma-ray sources were detected. At the same time, extragalactic sources in the gamma-quantum universe associated with active galaxies and quasars, where explosive processes occur, are tens of millions of times more powerful than supernova explosions. It is possible that modern astronomy is on the threshold of the discovery of a fundamentally new class of cosmic objects whose physical nature is still unknown to us. A very interesting gamma source in the universe was also discovered in the constellation Ophiuchus. In this place there is a dense gas-dust cloud, inside of which there is a group of young hot flare stars. Gamma quanta are also recorded from another nebula, the Orion Nebula, in which there are young stars and where, according to some data, there is an expansion of the systems of such stars-stellar associations.

Registration of cosmic gamma quanta of high energy in the universe, in principle, allows us to detect objects that are cosmic ray generators, that is, to solve a problem that has long been one of the most important in astrophysics. The point is that when interacting the energetic nuclei that make up cosmic rays, with the interstellar medium surrounding their source, particles of gas or dust, special elementary particles, the so-called pi-zero mesons, must be born. These particles are short-lived and decay into gamma quanta, which can be registered with gamma-ray telescopes. In this case, the gamma-luminescence is brighter, the greater the density of cosmic radiation. Thus, observations in the gamma range allow not only to determine where the object generating cosmic rays is located, but also to estimate its intensity.

The sources of gamma quanta in the universe are neutron stars - pulsars. In particular, the brightest "star" in the gamma range is a pulsar located in the constellation of Sails, invisible to optical telescopes. Another "gamma-star" is identified with the famous pulsar in the Crab nebula. However, there is still no direct evidence that vigorous nuclei are produced in pulsars and thus pulsars are the sources of cosmic rays. Most likely, the gamma-emission of pulsars is generated by fast electrons.

Further study of cosmic gamma quanta should provide answers to many questions that are of fundamental importance for understanding the structure of cosmic objects and the physical processes occurring in the universe. In particular, the fact that gamma quanta in the Universe propagate rectilinearly opens the possibility of not only detecting very distant sources of gamma radiation, but also determining the directions in which they are located. And since the mechanism of the origin of gamma quanta in the Universe is associated with the action of "nonthermal" particles of sufficiently high energy, this radiation carries with it extremely valuable information about the physical processes taking place in such regions of the Universe where there is a high concentration of nonthermal particles.