Rings of Dark Matter

Perhaps it was the same problem Zwicky had seen with the Coma Cluster, and Smith with the Virgo Cluster, and Oort with the Spindle Galaxy. Over the next decade, every galaxy studied had a flat rotation curve. Astrophysicists ran computational simulations of the dynamics of galaxies to study their motion. If our theory of gravity is correct over large scales, the whole Andromeda galaxy - as with perhaps most galaxies - is surrounded, submerged, and stabilized by enormous halos of unseen matter that increase in ratio to visible matter as you move outward from the center of the disk. This dark matter gives off very little or no light, yet represents not just some of what is out there, but the overwhelming majority of matter in the universe, perhaps ten times what can be seen. 

These results are incredible, and astronomers received it with incredible hostility; some thought that Ford and Rubin were ruining their career by pursuing it. Dark matter became the source of arguments at conferences. But eventually astronomers had no choice but to accept the overwhelming evidence that there was a serious problem. 

With a visible sigh, they began to theorize.