Accretion Disc

Within the Newtonian gravity only, it is hard to explain how the matter falls into the galactic nuclei without losing its angular momentum first. To explain this problem without invoking the additional long range gravity force, one has to introduce the friction and the hydrodynamic fluid equation as well as the concept of the plunge radius within which one has to assume that the matter falls into the nuclei without having the persistent rotational motion. In fact, the angular momentum is such a well conserved quantity that it is hard to get rid of it without a proper cause.

If we have an additional long range gravity force that depends on the function of 1/r^4 in the radial direction, the Virial theorem can not hold and the matter circling around the nuclei will not conserve the angular momentum and the orbit is not going to be closed.

The orbit of the matter circling around the galactic core with the additional long range dipole gravity force will become smaller and smaller with the increasing velocity until it plunges into the nuclei with a violent collision which may be the major cause of the observed gamma ray bursts. This also implies that the accretion debris is neither in a purely ionized plasma nor in the gaseous states.

By this way, the necessity of finding an alternative way to lose the angular momentum is totally unnecessary, let alone the assumption of the existence of the plunge radius. As discussed in the page black hole jet engine, the dipole gravity potential with its latitude angular dependency explains the mechanism on how the matter prefers to stay in the thin disk shaped region in the equatorial plane as well.

It is fundamentally caused by the lower dipole gravity potential formed around the equatorial plane due to the latitude angular dependency of the force. The heat of the material falling into the nuclei is caused by the continuous compressing force of dipole gravity toward the core of the galaxy, which is manifested by the attractive harmonic force of the (sign corrected) Lense-Thirring force at the center.

Within the entire picture of the spiral galaxies, the accretion disc is an integral part of the jets and the dark matter problem when dipole gravity is invoked for its explanation.