February saw the end of the second summer of operation by the Dark Energy Survey (DES) collaboration at the Victor M. Blanco Telescope in the Chilean Andes. Armed with a custom, state-of-the-art 570-megapixel camera, the collaboration is working to chart the 14-billion-year history of cosmic evolution. Over its five-year run, the survey will map more than 300 million galaxies in one-eighth of the night sky and will document an expected 3000 supernovae. Those data will provide key insights into the mysterious dark energy thought to be driving the universe’s accelerating expansion. (See the article by Josh Frieman, Physics Today, April 2014, page 28.)
One of the survey’s measurement tools is weak gravitational lensing: Light coming to us from distant galaxies gets slightly deflected by the gravitational field of massive objects along the way, so the galaxies appear distorted. (See the article by Leon Koopmans and Roger Blandford, Physics...