Why can't dark matter halos collapse to be the same size as the visible parts of galaxies?
A) Dark matter can't dissipate its energy through radiation from collisions.
B) Dark matter is made mostly of mini-black holes.
C) Dark matter has much more angular momentum.
D) Dark matter annihilates when it begins to get that dense.
E) Dark matter particles are too large to collapse that much.

Question

Quizplus · Accepted Answer

Dark matter does not interact electromagnetically, so it cannot lose energy through radiation and thus cannot collapse to form dense structures like the visible parts of galaxies.

Why Can't Dark Matter Halos Collapse to Be the Same