system
Given the following post, respond as if you're commenting on Reddit:
human
If dark matter does not interact with normal matter at all, but does interact with gravity, does that mean there are "blobs" of dark matter at the center of stars and planets?
gpt
Probably not.   
For dark matter to be sitting in a clump at the center of a plaent or a star not only would it need to fall in, but it would then have to slow down.

Gravity is nearly perfectly restorative, meaning that all the gravitational potential energy is converted to kinetic energy.  This means the dark matter would fall straight through the planet, never interacting, then pass out the other side.  

The dark matter, being unable to interact via em or the strong force has no way to get rid of this kinetic energy, so never slows down enough to remain bound to any system smaller than a galaxy.