V.3 No 1

43

On the nature of red shift of Metagalaxy

"The chemical constitution of the interstellar gas in the first approach appeared quite similar to that of the Sun and stellar atmospheres. The prevailing elements are hydrogen and helium, while the rest elements we can think the 'impurities' " [20, p. 31]. "The thorough analysis of spectra obtained with 'Copernicus' from the relatively near (distanced from us from 20 to 150 pc) stars with no redness caused by the space dust allowed to study the physical properties of highly rarefied interstellar medium that is between the clouds. In this case the intensity of interstellar absorption lines is very small. Mainly there were observed the resonance lines of singly ionised atoms. It makes an impression that in the between-the-cloud medium there is relatively less heavy elements than in the clouds. The concentration of hydrogen in the between-the-clouds medium varies in a quite wide range from 0,2 to 0,02 cm³ " [20, p. 41- 42].

The mentioned vast regions of the between-the-clouds medium alternate with the denser regions of interstellar gas, clouds and nebulas. If speaking, for instance, of our Galaxy, "the interstellar gas in Galaxy concentrates in a very thin layer near its plane of symmetry. The thickness of this layer does not exceed 200 pc, and the average concentration of particles in it is about 10 ^{- 24} g/cm³. Notice that the average density of the interstellar dust is about 100 times less" [20, p. 42].

As an illustration we show in Fig. 8 the diagram of distribution of the neutral hydrogen in our Galaxy. As we can see, comparatively dense regions (about 1 particle per 1 cm³ and more) are located in the region of Galactic nucleus. To the periphery the density falls to 0,05 particles per 1 cm³ and, most probably, remains such in the intergalactic space out of nebulas and clouds.

Fig. 8. Distribution of the neutral hydrogen in the Galaxy. C means the galactic nucleus, and S means the Sun [21, p. 115].

"Thus, the concentration of atoms of the interstellar gas is at least milliard times less than in the Earth atmosphere. The more paradoxical looks the statement that the interstellar gas is far from being vacuum… The interstellar gas is a continual, compressible medium, continuum. The laws of gas dynamics are fully applicable to it. Through this continual medium there propagate waves, for example, shock waves… This medium is enveloped in complex turbulent motion, usually petty 'ripples' travel in it… We have to keep in mind also that this medium has quite high conductance, as it is either fully (in the regions H II of ionised hydrogen) or partially (in the regions H I of neutral hydrogen) ionised" [20, p. 42]. The kinetic temperature of interstellar gas also varies in the most wide range from 10 000 K in regions H I to 5 K in the averaged interstellar medium. "In the interstellar space the average density of the radiant energy is about 1 electron-volt per cubic centimetre or 10^-12 erg/?m³ … The temperature of the interstellar medium, determined through the density of the radiation filling it, is extremely low - about few Kelvins" [20, p. 36].