Final answer:
The intense radio source near the center of the Milky Way is a supermassive black hole with a mass of about 4.6 million Msun. Astronomical calculations based on orbital periods and the mass of the Galaxy are used to infer dark matter's existence.
Step-by-step explanation:
The question is centered on the intense radio source near the center of the Milky Way, which is recognized as a supermassive black hole due to the measurements of the velocities of stars within a few light-days of the center. This black hole is surrounded by an accretion disk that emits radio radiation, which can be detected and allows astronomers to estimate its mass, approximately 4.6 million solar masses (Msun). Additionally, astronomical observations and calculations regarding the mass of the Galaxy, the orbital period of peripheral stars, and dark matter are discussed within this framework.
Astronomical observations imply that the Galaxy has a mass of about 8.0 x 10¹¹ solar masses, and computations for orbital periods help in the indirect detection of dark matter due to the discrepancies between expected and actual measurements. The description of orbital speeds, distances from the galactic center, and respective orbital periods supports the existence of a substantial amount of dark matter and illustrates the method for deducing the mass of the entire Milky Way galaxy.