Atacama Cosmology Telescope (image) Rutgers University Caption The Atacama Cosmology Telescope (ACT) in the Atacama Desert of northern Chile, with Cerro Toco volcanic peak in the background. Astronomers conducted a large, uniform survey of the southern sky with ACT, using a breakthrough technique that detects "shadows" of galaxy clusters on the cosmic microwave background radiation. The shadows pointed astronomers to previously unseen massive galaxy clusters. Credit Adam Hincks, Princeton University, University of Toronto Usage Restrictions Permission is granted to reproduce the image in connection with news coverage of this story. All other rights are reserved. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.