Shining new light on dark energy with galaxy clusters: "In its first season, the ACT team identified 23 clusters, approximately half of which were previously unknown. The discovery of new clusters highlights the power of CMB observations to spot extremely distant galaxy clusters. Once the galaxy clusters are discovered, optical wavelength observations are used to determine their distance. Sehgal led the effort to analyze the new data in order to distinguish between different competing dark energy theories.
'Each model for dark energy makes a prediction that you should see this many clusters, with this particular mass, this particular distance away from us,' Sehgal said."