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)
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 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.
Dark matter provides the gravity that 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 provides the gravity that allows the stars to rotate at the same speed.
The correct response is:
Dark matter provides the gravity that allows the stars to rotate at the same speed.
The correct answer is: Dark matter provides the gravity that allows the stars to rotate at the same speed.
To understand why this provides evidence of dark matter, we need to consider the laws of gravity and the observed behavior of stars in galaxies. According to Newton's laws of motion and gravity, the speed at which an object orbits around a central mass depends on the gravitational force pulling on it. In a galaxy, the central mass is located at the galaxy's center, and the stars in the galaxy are orbiting around it.
If we only consider the visible matter, such as stars and gas, in a galaxy, we would expect the orbital speeds of stars to decrease as you move away from the center. This is because the visible matter becomes less dense toward the edges of the galaxy, and therefore, there is less gravitational force pulling on the stars farther away from the center.
However, observations have shown that the stars at the edges of galaxies are rotating around the galaxy's center at similar speeds to the stars in the middle. This is surprising because if only visible matter were considered, the stars at the edges should be moving slower than the stars in the middle.
To explain this discrepancy, scientists propose the existence of dark matter. Dark matter is a hypothetical form of matter that does not emit, absorb, or reflect light, making it invisible to traditional astronomical observations. It only interacts with gravity and has a significant gravitational effect on visible matter.
The presence of dark matter provides the additional gravitational force necessary to maintain the observed uniform orbital speeds of stars as we move away from the center of the galaxy. Therefore, the fact that stars at the edges of galaxies are rotating at the same speed as stars in the middle is evidence for the existence of dark matter.