What behaviour of galactic rotation curves suggests the existence of dark matter in an extended halo?
A)Small velocities are seen at large distances from the galactic centre.
B)Small velocities are seen at distances close to the galactic centre.
C)Large velocities are seen at large distances from the galactic centre.
D)Large velocities are seen at distances close to the galactic centre.

Question

Quizplus · Accepted Answer

Galactic rotation curves show that the velocities of stars and gas increase as they move away from the galactic centre until a certain point, after which the velocities should decrease due to the decreasing gravitational pull of the galactic mass. However, observations have shown that the velocities continue to remain relatively constant at large distances, suggesting the presence of additional mass that is not visible but still interacts gravitationally with the visible matter. This additional mass is believed to be the dark matter in an extended halo that surrounds galaxies, causing the observed large velocities at large distances from the galactic centre.

What Behaviour of Galactic Rotation Curves Suggests the Existence of Dark