The European Space Agency has recently shared initial data from the Euclid space telescope’s mission, which aims to map the vast structure of the universe to enhance our understanding of dark energy and dark matter. Scientists revealed Euclid’s observations of three sections of the sky filled with galaxies. This data represents a sky survey equivalent to over 300 times the size of the moon as seen from Earth, a significant step towards creating a comprehensive atlas of the cosmos covering more than a third of the sky.
Launched in 2023 on a six-year mission, Euclid is an orbiting observatory that collects data on the universe’s expansion, structure formation, and the nature of dark energy and dark matter, as well as gravity’s role on large scales. While the disclosed survey areas account for a small portion of the mission’s overall objective, the data includes observations of 26 million galaxies up to 10.5 billion light-years away, offering insights into the universe’s composition and evolution.
The universe, born from the Big Bang around 13.8 billion years ago, consists of ordinary matter, dark matter, and dark energy. Ordinary matter, which comprises stars, planets, and familiar substances, makes up about 5% of the universe, while dark matter and dark energy account for approximately 27% and 68%, respectively. Euclid’s newly released images suggest the organization of galaxies within the cosmic web, revealing structures that provide clues about dark matter and dark energy.
Astrophysicist Carole Mundell, the European Space Agency’s director of science, describes Euclid as a “dark detective” exploring the unknown 95% of the universe. Using its high-resolution visible imaging instrument to study galaxy shapes and distribution and its near-infrared instrument to determine galaxy distances and masses, Euclid is expected to capture images of over 1.5 billion galaxies, surpassing previous sky surveys in exploring distant celestial objects.
Furthermore, Euclid’s research encompasses transient phenomena like supernovae, with a catalog of over 380,000 galaxies released detailing various shapes, sizes, and features. This catalog is a significant step towards compiling the most extensive record of galactic details to date.
University of Toronto astrophysicist Mike Walmsley, a member of the Euclid team, discussed the significance of studying the appearance of galaxies. When light reaches us from distant galaxies, it gets bent and distorted by normal and dark matter in the foreground, a phenomenon known as gravitational lensing. This effect plays a crucial role in helping researchers analyze the distribution of dark matter. By examining the Euclid data, scientists have pinpointed approximately 500 potential strong gravitational lenses.
Walmsley explained that invisible dark matter within massive galaxies alters the fabric of space, causing light to curve like a magnifying glass. This distortion results in the formation of arcs and rings when observing galaxies positioned behind the massive ones. By studying these distortions, researchers can gain insights into the presence of dark matter. However, such strong lensing occurrences are rare due to the precise alignment required between the galaxies.
Euclid stands out as a premier tool for detecting these gravitational lenses because of its ability to capture high-resolution images of expansive areas in the sky. In contrast, telescopes like Hubble and the James Webb Space Telescope focus on smaller sections of the sky. The forthcoming Euclid data release in October 2026 is expected to cover an area 30 times larger than the most recent release.
