The European Space Agency’s Euclid mission, launched in July 2023, has released its first major dataset covering 14% of the sky. This release identifies over 900 million galaxies and more than 60 million potential quasars, which are blazing objects powered by supermassive black holes at the centers of distant galaxies. The data also includes about 15,000 probable cases of strong gravitational lensing, a phenomenon where foreground mass bends light from background sources. Prof Andy Taylor of the University of Edinburgh describes this as "the biggest high-resolution image of the universe we’ve ever had." He notes that while larger surveys exist, none match Euclid’s combination of detail and information content across such vast volumes of the cosmos.
Probing Dark Matter Clumps
Strong gravitational lensing acts as a diagnostic tool for dark matter properties. Stephen Serjeant, a professor at the Open University, explains that different types of matter clump in distinct ways, making the effect highly informative. "With strong gravitational lensing, you find out how the dark matter is clumping and that’s very diagnostic of the type of matter that it is," Serjeant says. He reports there is a good chance the next breakthrough regarding dark matter identity may come from these observations. Previously, experts knew of only about 1,000 such cases, but Euclid’s current data reveals 15,000 probable instances. Researchers expect to discover an estimated 170,000 cases by the end of the mission. This volume allows scientists to rule out specific theories on how this mysterious substance distributes itself within galaxy clusters.
Mapping the Invisible
A further data release is expected next summer, incorporating results on weak gravitational lensing. This subtle distortion pattern enables researchers to map the location of all dark matter in the universe. Taylor states that scientists can then work out statistical properties and compare them with theoretical models. "Depending on the type of dark matter, the type of dark energy, we’re expecting to see slightly different patterns on the sky," he said. The sheer scale of the dataset presents a practical challenge, as no human eyeball can process all the information anymore. It is now too big for manual review, requiring automated tools to explore the new phenomena. The mission aims to shed light on dark energy and dark matter, which together make up about 95% of the universe.
