OUR COSMOS

The claims are based on observations of the Bullet Cluster.

Team finds 'proof' of dark matter

Until now, astronomers have only been able to infer the existence of dark material through the gravitational effects it has on ordinary matter.
Researchers have now discovered what is effectively the gravitational signature of dark matter created by dark matter and ordinary matter being wrenched apart by the immense collision of two large galaxy clusters.
In the cosmic smash-up known to astronomers as the Bullet Cluster, these components have been pulled apart.
The astronomers were lucky enough to catch the collision just 100 million years after it occurred -- the blink of an eye in cosmic time.