Question

Which of the following statements best describes the mass in the outer parts of the Milky Way (beyond the orbit of the sun)?

A. Most of the mass is due to a super-massive black hole
B.There is essentially no mass out there
C.The outer part of the galaxy is rapidly evaporating into intergalactic space
D. It emits a surprisingly small amount of light

Answer 1

The mass in the outer parts of the Milky Way emits a surprisingly small amount of light because it is largely composed of dark matter, which is detected through its gravitational effects rather than emission of light.

Step-by-step explanation:

The statement that best describes the mass in the outer parts of the Milky Way beyond the orbit of the sun is that it emits a surprisingly small amount of light. This is because a significant portion of the mass in the outer regions of the Milky Way is composed of dark matter, which does not emit light and cannot be seen with telescopes. Unlike the supermassive black hole at the center of the Milky Way, which contains a mass equivalent to 4.6 million Suns, the dark matter extends well beyond the luminous stars, out to at least 200,000 light-years from the center. Although we cannot directly observe dark matter, its presence is inferred from its gravitational effects on the motions of stars and galaxies. There is approximately nine times more dark matter than visible matter within the Milky Way, which is crucial for explaining the rapid orbits of stars in its outer regions.