The stars at the edges of a galaxy are rotating around the galaxy’s center at the same speed as the stars in the middle of the galaxy. How does this provide evidence of dark matter?(1 point)

Question

Responses

Dark matter emits the light that astronomers need to see the orbital speeds of the stars.
Dark matter emits the light that astronomers need to see the orbital speeds of the stars.

Dark matter subtracts gravity, which allows the stars to rotate at the same speed.
Dark matter subtracts gravity, which allows the stars to rotate at the same speed.

Dark matter absorbs light from outside the galaxy, allowing the light of the stars in the galaxy to show the orbital speeds of the stars.
Dark matter absorbs light from outside the galaxy, allowing the light of the stars in the galaxy to show the orbital speeds of the stars.

Dark matter provides the gravity that allows the stars to rotate at the same speed.

Answer 1

The correct response is:

Dark matter provides the gravity that allows the stars to rotate at the same speed.

This observation is significant because, in a galaxy without dark matter, we would expect the stars at the edges to move slower than those at the center since gravitational pull decreases with distance from the center. The fact that stars at varying distances from the center are rotating at similar speeds suggests the presence of additional unseen mass—namely, dark matter—providing the necessary gravitational pull to keep them moving at those speeds.