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 collisions.
B) Dark matter is mostly made of mini-black holes.
C) Dark matter has much more angular momentum.
D) Dark matter annihilates when it begins to get that dense.

Question

Quizplus · Accepted Answer

Dark matter does not interact electromagnetically, so it cannot lose energy through collisions and radiation like normal matter, preventing it from collapsing to the same size as the visible parts of galaxies.

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