sight19 t1_jdx0z40 wrote on March 27, 2023 at 8:29 PM

Reply to comment by arcanum7123 in Black holes may be swallowing invisible matter that slows the movement of stars by trevor25

For structure to form, you need to compress gas in a small volume. As gas is compressed, it's temperature increases and so do the random motions of the theoreticized WIMPs. That means that at a certain point, the gas cloud stops collapsing (this is also called 'virialization'). The only way to collapse further is if the gas cloud would leak out temperature somehow, and that can only happen via radiation. And dark matter can't radiate, so it can't cool further

ThrowawayPhysicist1 t1_jdx8ewv wrote on March 27, 2023 at 9:17 PM

This is a good explanation but there’s also just the simpler fact that if things can’t collide (and dark matter is mostly collisionless as famously seen in the bullet cluster) it’s hard to get it to “stick together”. So while gravitational force will get it form “dense halos” it’s fairly unlikely you’ll get something like planets or stars.