Question

What evidence do we have that there is dark matter in the galaxy?

A. Missing neutrinos from the sun
B. RR Lyrae variable stars in globular clusters
C. Flat rotation curves far from the center of the galaxy
D. Cool clouds of hydrogen gas

Answer 1

The evidence for the existence of dark matter in the galaxy includes flat rotation curves, presence of cool clouds of hydrogen gas, and missing neutrinos from the sun.

Step-by-step explanation:

The evidence for the existence of dark matter in the galaxy includes:

1. Flat rotation curves far from the center of the galaxy: The velocities of stars in a spiral galaxy do not decrease as expected if the matter were concentrated in luminous stars. Instead, the velocity curve is almost flat, indicating the presence of a massive galactic halo of dark matter extending beyond the visible stars.
2. Cool clouds of hydrogen gas: Observations of X rays from galactic clusters reveal the presence of hot clouds of ionized gas in space that was previously considered empty. This indicates the presence of dark matter.
3. Missing neutrinos from the sun: Neutrinos, which are subatomic particles, have been observed to be missing from the sun. If neutrinos were the only dark matter, their absence from the sun supports the idea of dark matter existing in the galaxy.