V.4 No 1

63

On orbital stability of oscillators

As an example, in Fig. 22 we show a trivial galaxy ESO 510 G13 with spherical nucleus and well formed dense dust disk.

a

b

Fig. 22. Dusty spiral galaxy ESO 510 G13: a - positive image, b - negative. The image has been copied at http://photojournal.jpl.nasa.gov/jpegMod/PIA04213_modest.jpg

The authors of this image interpret it so: "The galaxy's outer regions, especially on the right side of the image, show dark dust and bright clouds of blue stars. This indicates that hot, young stars are forming in the twisted disc. Astronomers believe star formation may be triggered when galaxies collide and their interstellar clouds are compressed" [20]. But the very fact that star formation occurs in the disk tells that this disk has a spiral shape which we do not see because we see this galaxy sideways.

Not only the spiral-shaped disk is interesting in this galaxy. As we said above, galaxies with spherical nuclei have not so large angle of precession as elliptic have. To see the shape of dynamic vibrations of ESO 510 G13, conveniently see its image in negative. Then we see that the disk of ESO 510 G13 appears thin and quite plane, but the main, in its rotation together with the nucleus, it vibrates across its plane. The pattern of these vibrations is actually alike those of an elastic disk, and this corroborates the above expressed opinion: vibrations of galactic disk can be transverse but not radial. These vibrations are just the kind of precession typical for galaxies with spherical nuclei. As opposite to this, the disk of galaxy with elliptic nucleus (see Fig. 19) has a shape of triangle and precesses relatively the rotation axis as an integer system, just as we see it in Fig. 19b.

As we see, the very appearance of the disk, the pattern of precession and of transverse vibrations in the galactic disk can tell us quite much about the processes occurring in its nucleus.