Comment 1 by Schrodinger's Cat :

I'm not clear what they mean by dark matter in 'the space around the Solar System'. Given that dark matter supposedly does not interact other than gravitationally, why should one suppose that it is rotating along with the matter to the extent that there'd be any noticeable long term effect ?

From the article discussing this on the website I mentioned above:

"Their approach is to study the gravitational effects of nearby matter, as reflected by the motions of a small sample of the stars that lie within a few thousand light years of the sun. [Sorry -- I still don't understand their method well enough to explain it to non-experts, but will fill in more details if and when I do.] . And they claim that the motions of those stars suggest that the only matter nearby is the ordinary matter we can see around us, with no dark matter in addition."

Hope that helps.