I just read a text about astronomy and when talking about dark matter the author says:
[...], the dark matter responsible for the orbits of the stars in the Milky Way is probably different from the dark matter responsible for the orbit of the Milky Way within the local super-cluster of galaxies.
Is this true? How would it be different? And why?
For context, this is the whole paragraph:
Since the 1930's astronomers have measured the orbits of galaxies in clusters of galaxies, clusters of galaxies in clusters of clusters, and so forth. They have found similar anomalies in the angular velocity of galaxies at these larger scales. Again the anomalous high angular velocities of the galaxies and clusters of galaxies may be explained by postulating a mysterious dark matter that fills the universe. It is doubtful that one can explain the anomalous angular velocities at different scales by the same type of dark matter. Thus, the dark matter responsible for the orbits of the stars in the Milky Way is probably different from the dark matter responsible for the orbit of the Milky Way within the local super-cluster of galaxies.
And the article can be found here: https://mathblog.com/wp-content/uploads/2009/12/Keplers-New-Astronomy.pdf