Euclid Telescope’s First Survey Finds 26 Million Galaxies in Only One Week

Mar 19, 2025

Jeremy Gray

A grid of diverse spiral galaxies captured by the Hubble Space Telescope. Each square displays a galaxy in various orientations and formations, showcasing bright cores, swirling arms, and cosmic dust against a dark background. — This mosaic shows galaxies in different shapes captured by Euclid during its first observations of the Deep Field areas. The European Space Agency released a detailed catalog of more than 380,000 galaxies as part of this initial data release.

The first survey data from the 600-megapixel Euclid space telescope is available now. The European Space Agency (ESA)’s data release features classified, detailed images of 380,000 galaxies and provide a look at the large-scale organization of the Universe’s cosmic web. Euclid observed 26 million galaxies in total in just one week.

The data release covers a massive area of the sky captured in three mosaics. These sections show numerous galaxy clusters, active galactic nuclei, and other transient events. Alongside the raw data release, there is a new classification of more than 380,000 galaxies and 500 gravitational lens candidates selected in part by artificial intelligence and citizen scientists.

“Euclid shows itself once again to be the ultimate discovery machine. It is surveying galaxies on the grandest scale, enabling us to explore our cosmic history and the invisible forces shaping our Universe,” ESA’s Director of Science, Professor Carole Mundell.

A detailed image of the night sky filled with countless tiny stars and clusters, set against a deep black background. The arrangement forms a slightly irregular geometric pattern around the edges. — ‘This is Euclid’s Deep Field North. After only one observation, the space telescope has already spotted more than ten million galaxies in this field. It is also very rich in Milky Way stars, as it is close to the Galactic plane. In the coming years, Euclid will make 32 observations of this field to reach its full depth. ‘

A vast view of the night sky filled with numerous stars of varying brightness against a dark background. The stars are scattered randomly, creating a dense, starry pattern. The image has a slightly irregular border. — ‘This is Euclid’s Deep Field Fornax. After only one observation, the space telescope already spotted 4.5 million galaxies in this field. In the coming years, Euclid will make 52 observations of this field to reach its full depth.’ This section spans 12.1 square degrees and is located in the southern constellation Fornax.

A mosaic of the night sky showing a dense field of stars and distant galaxies. The image is composed of several rectangular segments arranged to form an elongated, rectangular shape against a black background. — ‘This is Euclid’s Deep Field South. After only one observation, the space telescope already spotted more than 11 million galaxies in this field. In the coming years, Euclid will make more observations of this field to reach its full depth.’ This field covers 28.1 square degrees in the southern constellation of Horologium and has never before been covered by any deep sky survey.

A colorful panoramic view of the Milky Way galaxy, with bright white and blue hues. The central band is dense and bright, surrounded by wispy blue regions. Yellow highlights are scattered on the dark background. — This graphic shows the location of the Euclid Deep Fields (yellow) on the ESA’s Gaia star and Planck dust maps.

“With the release of the first data from Euclid’s survey, we are unlocking a treasure trove of information for scientists to dive into and tackle some of the most intriguing questions in modern science. With this, ESA is delivering on its commitment to enable scientific progress for generations to come,” Mundell continues.

Euclid scouted three areas in the sky where the approximately $1.5 billion telescope will focus its mission efforts. So far, in just one week of observations and only a single scan per region, Euclid saw 26 million galaxies, the most distant of which are up to 10.5 billion light-years away. The selected fields also include other fascinating cosmic objects, including bright quasars.

A vast starry sky filled with numerous bright stars and distant galaxies scattered across a dark background. Various star intensities create a sense of depth, presenting an expansive view of the Universe. — This is a zoomed-in area of Euclid’s Deep Field South. It is zoomed in 16 times compared to the large mosaic.

Euclid will pass over these three regions tens of times in the coming years, per the ESA. Before the nominal mission ends in 2030, Euclid will photograph even more distant galaxies in the deep reaches of space.

“But the first glimpse of 63 square degrees of the sky, the equivalent area of more than 300 times the full Moon, already gives an impressive preview of the scale of Euclid’s grand cosmic atlas when the mission is complete,” the European Space Agency explains. “This atlas will cover one-third of the entire sky — 14,000 square degrees — in this high-quality detail.”

A deep space image showing numerous galaxies and stars scattered across the blackness of space. A bright spiral galaxy is visible in the lower right, with twinkling stars and dense cosmic clusters throughout the scene. — This is that same area in Euclid’s Deep Field South at a 70 times zoom.

This initial data based on just one observation has already provided scientists with rich information concerning galaxy shapes, gravitational lenses, clusters, star formation, and more.

“We will observe each deep field between 30 and 52 times over Euclid’s six year mission, each time improving the resolution of how we see those areas, and the number of objects we manage to observe. Just think of the discoveries that await us,” says Valeria Pettorino, ESA’s Euclid project scientist.

Using its high-resolution visible instrument (VIS) and near-infrared instrument (NISP), Euclid will deliver precise measurements and details concerning the shapes and distribution of billions of galaxies in the Universe. How these galaxies are distributed and organized will provide insights into dark matter, the origin of galaxies, and the Universe’s distant past. Scientists believe dark matter and dark energy make up 95% of the Universe, and Euclid is designed to help understand all that very mysterious matter.

A deep space image showing a luminous galaxy at the center surrounded by faint, stringy red filaments. The background is filled with numerous stars and distant galaxies on a dark sky. — Euclid’s view of the Cat’s Eye Nebula. This is a zoomed-in section of Euclid’s Deep Field North.

“The full potential of Euclid to learn more about dark matter and dark energy from the large-scale structure of the cosmic web will be reached only when it has completed its entire survey. Yet the volume of this first data release already offers us a unique first glance at the large-scale organization of galaxies, which we can use to learn more about galaxy formation over time,” says Clotilde Laigle, Euclid Consortium scientist and data processing expert based at the Institut d’Astrophysique de Paris, France.

Euclid’s first catalog features just 0.4% of the total number of galaxies that Euclid is expected to image with similar resolution during its mission. The final catalog will showcase the detailed morphology of at least an order of magnitude more galaxies than ever measured before.

A grid of various galaxy images, each showcasing different shapes, sizes, and colors. Galaxies display spirals, ellipses, and irregular forms set against a dark background speckled with stars. — With the aid of citizen scientists and precise AI models, ESA shared this selection of 500 galaxy-galaxy strong lens candidates, nearly all of which where previously unknown. This type of galaxy-galaxy lensing occurs when a foreground galaxy and its halo of dark matter act as a lens that distorts the light from a background galaxy along Euclid’s line of sight.

“We’re looking at galaxies from inside to out, from how their internal structures govern their evolution to how the external environment shapes their transformation over time,” Laigle adds.

“Euclid is a goldmine of data and its impact will be far-reaching, from galaxy evolution to the bigger-picture cosmology goals of the mission.”

Image credits: European Space Agency. Detailed information concerning the data release is available on the ESA’s Cosmos science mission website. The ESA has also published explorable Euclid deep field data: Euclid Deep Field North, Euclid Deep Field Fornax, and Euclid Deep Field South.