ESA’s Euclid mission is designed to bring the dark side of the Universe to light. Based on the way galaxies rotate and orbit one another, and the way in which the Universe is expanding, astronomers believe that two unseen entities dominate the composition of our cosmos. They call these mysterious components dark matter and dark energy, yet to date we have not been able to detect either of them directly, only inferring their presence from the effects they have on the Universe at large.

To better understand what dark matter and dark energy may be, we need a mission that can more closely reveal what effects they have had on galaxies, galaxy clusters and the expansion of the Universe itself. Euclid is that mission.

ESA’s Euclid mission will create a 3D-map of the Universe, with the third dimension representing time itself. The further away a galaxy is located, the longer its light has taken to reach us and so the earlier in cosmic history we will see it. By observing billions of galaxies out to a distance of 10 billion light-years, scientists will be able to chart the position and velocity of galaxies over immense distances and through most of cosmic history, and trace the way the Universe has expanded during that time. Euclid’s extraordinary optics will also reveal subtle distortions in the appearance of galaxies.

From this wealth of new data, astronomers will be able to infer the properties of dark energy and dark matter more precisely than ever before. This will help theorists pin down the nature of these mysterious components and develop a refined understanding of how gravity behaves at the largest distances.