degenerate orbit. Consequently, in a SFNS spacetime, ’slow’ particles of matter, which rest on the static degenerate orbit or slowly move near it, will form a gravitationally bound cluster. One can expect that most of the energy of particles, falling into this shell with initially high relative velocities, will be radiated to infinity. If the accretion flow onto the inner region is negligible or at least sufficiently small, as in the central region of Sgr A\*, then only collisions and radiative processes determine the time evolution of the cluster. Eventually the cluster will cool down and then become a spherical shell consisting of cold gas, dust, or fluid. Therefore, this shell will be seen by a distant observer as a shadow or a gray spot, which can be mistakenly taken for the shadow of a black hole.

And third, we have studied the shape of orbits close to the centres of SFNSs and shown that their angles of precession are negative, that is, pericentre retreats during each orbital revolution, and not advances as in the case of Schwarzschild black holes. At the present time, we can observe only the orbits of S-stars in the distant region of the Galactic center. 