Final answer:
The black hole at the center of the Milky Way has a mass of approximately 4.6 million solar masses, classifying it as a supermassive black hole.
Step-by-step explanation:
The black hole at the center of the Milky Way has a mass of about 4.6 million solar masses. This makes it a supermassive black hole, a type of black hole that contains mass far greater than that of a typical black hole resulting from the death of a single star. This mass concentration is confined within a volume with a diameter no larger than the orbit of Mercury, confirming the supermassive black hole's presence at the heart of our galaxy through various observations, including those from the Hubble Space Telescope and radio telescopes.