Final answer:
The mass estimate of dark matter in the Milky Way is approximately 10 times the mass of the luminous matter, which is made up of stars.
Step-by-step explanation:
The mass of dark matter in the Milky Way galaxy is a significant component of its total mass. Observations of orbital velocities indicate that while the luminous matter, comprised of stars that emit electromagnetic radiation, contributes to the galaxy's mass, an enormous proportion consists of dark matter. This dark matter, which does not emit electromagnetic radiation, can only be detected through the gravitational forces it exerts.
Considering the luminous matter due to approximately 10¹¹ stars with an average mass 1.5 times that of our Sun, and assuming that dark matter is 10 times as massive as this luminous matter, the mass estimate of dark matter is about 10 times the mass of the luminous matter in the galaxy.