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S.B. Karavashkin and O.N. Karavashkina

At the same time, multiple formation of spiral arms is not a distinctive property of non-compact galaxies. In compact galaxies the formation of multiple charge centres is also possible, but the appearance of these galaxies will essentially differ from those shown before. As an example, see in Fig. 27 the image of such compact galaxy with the double centre of charge.

a

b

Fig. 27. Spiral galaxy M 51 with the double centre of charge and compact nucleus: a - positive image, b - negative. The image has been copied at   http://heritage.stsci.edu/2001/10/index.html

In this image we can see the well formed galaxy, from the nucleus of which two arms diverge. The lead of spirals says us that it rotates slowly, but the radius of the orbit of charge centres is very large. If we compare the shape of spirals of this galaxy with the diagram of double spiral in Fig. 26, we will see that the field of M 51 is practically ideal. The substance of periphery almost fully has concentrated in the spiral arms, and now an active star formation takes place in them. Especially clearly we can see it in the positive image shown in Fig. 27a.

The negative image shown in Fig. 27b some opens us another side of processes in the dynamic field. We see that the space between the arms is not empty, it is filled with the interstellar medium having some structure, which tells us that force fields are present in this region. This to a definite extent corroborates the above statement that for negatively charged ions of interstellar gas and dust, the minimum of potential energy will lay namely between the arms. In the image we just see, how the gas-dust negatively charged nebula gets its structure in the region of maximal dynamic potential of the positive charge of the field source of the nucleus.