Final answer:
Observations have shown a close correlation between the mass of the central black hole in a galaxy and the mass of the host galaxy's central bulge of stars. The black hole and the host galaxy can impact each other's growth. The mass of the central black hole is often about 1/200th the mass of the stars surrounding it.
Step-by-step explanation:
Observations have shown a close correlation between the mass of the central black hole in a galaxy and the mass of the host galaxy's central bulge of stars. This correlation exists in both elliptical galaxies and the central bulges of spiral galaxies.
Although the exact reason for this correlation is still unknown, scientists have found that the black hole can influence the rate of star formation in the galaxy, and the properties of the surrounding galaxy can affect the growth of the black hole. Studies have also revealed that the mass of the central black hole is often about 1/200th the mass of the stars surrounding it.