A supermassive black hole at the center of the Milky Way;

There is compelling evidence that the extremely compact non-thermal radio source at the center of our Milky Way Galaxy, Sagittarius A* ( Sgr A*), is a best known supermassive black hole candidate with a dark mass of 4 million solar masses.

The single black hole-accretion disk precession model or disk-driven precession model is discussed carefully; Two correlations have been raised and sustained by observational values, which are precession period - absolute magnitude correlation and black hole mass - precession cone semi-angle correlation; A comparison between disk-driven bl.

Dark mini-halos, micro-halos and intermediate-mass black holes in the solar neighborhood;