Dark matter mapped in an area covering 2 million galaxies

Nature : Dark matter, the material that makes up the majority of the mass of the universe, has been mapped in small regions around galaxies many times. Now, Chihway Chang of the Swiss Federal Institute of Technology in Zurich and his colleagues have mapped dark matter in an area of the southern sky that is roughly equal to the angular area of 700 Suns. As part of the Dark Energy Survey (DES), Chang’s team used the 570-megapixel camera of the Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile to map the way that dark matter bends galactic light. The variations in the light from the most distant objects revealed the presence of dark matter in the intervening spaces. The resulting map of dark matter compares favorably with other maps of the universe’s underlying structure. This is the first data presented from DES and constitutes only 3% of the area that the survey is planned to cover by the time it is complete in 2018.