Final answer:
Ground-based observations and the Hubble Space Telescope have provided evidence of a supermassive black hole at the center of the Milky Way galaxy with a mass of about 4 million times that of the Sun.
Step-by-step explanation:
Black holes in crowded regions can grow and eventually swallow massive amounts of mass. Ground-based observations and the Hubble Space Telescope have provided evidence of a supermassive black hole at the center of the Milky Way galaxy with a mass of about 4 million times that of the Sun. These black holes can contain more than a billion solar masses and may be responsible for energetic phenomena in the universe. Recent X-ray observations also indicate the existence of intermediate-mass black holes.