The light and dark Universe

ESA’s Euclid mission aims to uncover the mysteries of the ‘dark’ Universe. This ominous-sounding invisible part of the cosmos makes up more than 95% of the mass and energy in our Universe.

For centuries, astronomers have aimed to learn more about the luminous sources of the cosmos: planets, stars, galaxies and gas, for example. But these objects make up only a small fraction of what the Universe contains.

95% of the Universe appears to be made up of unknown ‘dark’ matter and energy. Scientists estimate that dark matter makes up about 25% of the Universe and dark energy 70%. Dark matter and energy affect the motion and distribution of visible sources, but do not emit, absorb, or reflect any light, and scientists do not know yet what these entities actually are. Understanding their nature is therefore one of the most compelling challenges of cosmology and fundamental physics today.

Euclid is a European mission, built and operated by ESA, with contributions from NASA. The Euclid Consortium is responsible for providing the scientific instruments and scientific data analysis. ESA selected Thales Alenia Space as prime contractor for the construction of the satellite and its service module, with Airbus Defence and Space chosen to develop the payload module, including the telescope. NASA provided the detectors of the Near-Infrared Spectrometer and Photometer, NISP. Euclid is a medium-class mission in ESA’s Cosmic Vision Programme.