Mapping the invisible: how one telescope is charting the dark universe

Space · Published 18 October 2026 Swipe more like this →

In short: Most of our universe is invisible. To understand the mysterious forces of dark energy and dark matter, the Euclid mission is performing a massive, six-year survey, measuring the shapes and distances of billions of galaxies to reconstruct the history of cosmic expansion.

With substantial NASA involvement, the ESA mission Euclid began its journey on 1 July 2023, occupying a halo orbit near the Sun-Earth L2 point. Located approximately 1.5 million kilometres beyond Earth's orbit, the telescope is designed to remain operational for at least six years. Its primary objective is to probe the geometry and nature of the 'dark Universe' by investigating the accelerating expansion of the cosmos.

The mission employs sophisticated instruments, including a 600-megapixel camera for visible light and a near-infrared spectrometer and photometer. By measuring the shapes of roughly 1.5 billion galaxies and determining the redshifts—and thus the distances—of about 30 million galaxies, Euclid aims to create an extensive 3D map of the universe. This process allows astronomers to look back approximately 10 billion years into the past, observing how cosmic structures formed over time.

To detect the invisible, Euclid relies on complex physical phenomena. It uses gravitational lensing, where the presence of matter modifies the curvature of space-time and deflects light rays, to infer the distribution of dark matter. By studying the relationship between galactic shapes and redshift, and utilizing methods like baryon acoustic oscillations and spectroscopy, the mission seeks to understand how dark energy contributes to the universe's increasing acceleration. All validated data is expected to be released to the global research community within about two years of its acquisition.

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