Dark matter mapped using light from 100 million galaxies

The largest ever map of dark matter - invisible matter thought to account for 80% of the total matter of the Universe - has been created by a team co-led by UCL researchers, as part of the international Dark Energy Survey (DES). As matter curves space-time, astronomers are able to map its existence by looking at light travelling to Earth from distant galaxies; if the light has been distorted, this means there is matter in the foreground, bending the light as it comes towards us. The team used artificial intelligence methods to analyse images of 100 million galaxies, looking at their shape - spots of light made up of 10 or so pixels - to see if they have been stretched. The new map, a representation of all matter detected in the foreground of the observed galaxies, covers a quarter of the sky of the Southern Hemisphere. It is described in a new paper posted on the DES website and to be published in the Monthly Notices of the Royal Astronomical Society . Co-lead author Dr Niall Jeffrey (both at École Normale Supérieure, Paris, and UCL Physics & Astronomy) said: "Most of the matter in the Universe is dark matter. It is a real wonder to get a glimpse of these vast, hidden structures across a large portion of the night sky.