Roughly 15,000 strong gravitational-lensing candidates have been identified in a Euclid survey covering about 14% of the sky area planned for its six-year program. These are candidates, not confirmed lenses, but the resulting catalog is described as the largest of its kind.
The European Space Agency (ESA) has released the space telescope’s first major observational dataset, DR1-Foundation, containing data on more than 900 million galaxies. Hungarian researchers contributed to the survey, according to a statement from the HUN-REN Research Centre for Astronomy and Earth Sciences (CSFK). The center described the release, which brings together more than a year of observations, as “an important milestone in mapping the large-scale structure of the universe in three dimensions.”
Machine-learning methods, volunteers and experts helped identify the strong-lensing candidates. Gravitational lensing and the spatial distribution of galaxies are central to Euclid’s primary mission: studying dark matter and dark energy, which together account for approximately 95% of the universe’s total matter and energy content.
The release covers 1,900 square degrees of sky, equivalent to the apparent area of roughly 9,500 full moons. Alongside the galaxy data and lensing candidates, it contains more than 60 million quasar candidates. Spectra of more than 160 million celestial objects supplement the images and catalogs. The dataset totals approximately 1.7 million gigabytes and is described in the announcement as the largest sky survey of this kind conducted with a space telescope.
Valeria Pettorino, ESA’s Euclid project scientist, highlighted the increase in scale. Earlier releases contained only a few days of observations across about 60 square degrees. Publishing more than a year’s observations over a much larger area opens the way to breakthrough scientific results, she said.
Turning those observations into a three-dimensional map takes more than recording where galaxies appear in an image. Euclid’s near-infrared instrument splits the light from thousands of objects at once into its component wavelengths. These spectra allow researchers to determine galaxies’ distances and place them within the cosmic web, the network that forms the universe’s large-scale structure. Related studies also present maps of star-forming regions and investigations of gas movements within galaxies.
András Kovács, a researcher at the HUN-REN CSFK Konkoly Thege Miklós Astronomical Institute and head of Hungary’s Euclid team, said his Lendület research group studies this galaxy-built cosmic web. According to Kovács, mapping galaxies’ spatial distribution in greater detail than ever before allows researchers to track the network’s evolution more precisely. That is fundamental to understanding the roles of dark matter and dark energy.
Illustration of the Euclid space telescope. Credit: ESA.
Launched in 2023, Euclid has yet to deliver its completed map. As reported by MTI and Reuters, DR1-Foundation forms the basis for the full DR1 dataset planned for mid-2027, which will add further cosmological analyses to the current data.
