Question

Which discovery by astronomer Vera Rubin helped prove the existence of dark matter?

Galaxies exist outside of the Milky Way.
The expansion of the universe is accelerating.
Galaxies spin faster than they should, based on their visible matter.
Gas giants form farther from the Sun, where temperatures are cooler.

Answer 1

Explanation:

Astronomer Vera Rubin changed the way we think of the universe by showing that galaxies are mostly dark matter. On a dry and clear night at the Kitt Peak Observatory in the mountains of southern Arizona, Rubin closely observed the spectra of stars in the Andromeda Galaxy to determine their velocities.

Rubin and Ford went on to study some sixty spiral galaxies and always found the same thing. “What you see in a spiral galaxy,” Rubin concluded, “is not what you get.” Her calculations showed that galaxies must contain about ten times as much “dark” mass as can be accounted for by the visible stars

Answer 2

Answer: Galaxies spin faster than they should based on their visible matter

Explanation: i got it right