The way dark matter is introduced to documentary watchers such as myself is to account for the difference between the rotational velocity of the stars in a galaxy compared to that of planets in stellar systems or even planetary systems (e.g. Jovian moons).
There is an apparent paradox here however: stellar and planetary systems do live in galaxies as well, right? So that these smaller systems should not exhibit any difference of velocity curves.
Said otherwise, one could jokingly ask: does dark matter mischievously avoid stellar systems (just to give us a clue and get noticed at last I presume).
Browsing through this forum to get some answer I stumbled upon this former question distribution of dark matter and I thought that was the explanation: dark matter would be mainly confined to the outer rim of galaxies.
But then I also came across this other question is dark matter really present around the sun.
I think I really need some insight of people more in the know.