Editing Einstein Observatory (section)

===Galaxy clusters===
The [[Uhuru (satellite)|Uhuru]] satellite discovered x-ray emissions from a hot, thin gas pervading distant [[galaxy cluster|clusters of galaxies]]. Einstein was able to observe this gas in greater detail. Einstein data indicated that the containment of this gas within these clusters by gravity could not be explained by the visible matter within those clusters, which provided further evidence for studies of [[dark matter]]. Observations by Einstein also helped to determine the frequency of irregularly-shaped clusters compared to round, uniform clusters.{{sfn |Tucker |Tucker |1986 |p=93-95}}