Euclid releases 1.7 petabytes of survey data cataloguing 900 million galaxies

When the European Space Agency launched Euclid in July 2023, the spacecraft carried a simple but enormous ambition: to survey a third of the sky and reach back more than 10 billion years, in order to work out why the expansion of the universe is speeding up rather than slowing down. Euclid is a survey machine rather than a conventional camera, built to record hundreds of millions of galaxies at high resolution and then to use their shapes and positions as a set of cosmic rulers. On November 12, 2026, that effort produced its first substantial harvest.

The target of the mission is the so called dark universe. Ordinary matter, the material of stars, planets and gas, accounts for only about 5% of the universe, according to figures cited by Reuters, while dark matter makes up about 27% and dark energy about 68%. Nobody has observed either dark component directly. Astronomers infer them from the way galaxies move, cluster and bend light. Euclid was designed to turn those inferences into precise maps, and the new release is the largest step yet toward that goal.

Earlier Euclid data releases covered only a few days of observations, which made them useful for checking instruments but far too small for cosmology. The batch published on November 12, named DR1-Foundation, is a different order of thing. It draws on roughly 13 months of observations made between spring 2024 and spring 2025, and it is the first major release of nominal survey data since the telescope left the ground in mid 2023. The European Space Agency published the contents through its Euclid Cosmos portal.

The numbers attached to the release are hard to absorb. DR1-Foundation contains 1.7 petabytes of data, or 1.7 million gigabytes, gathered from the Euclid Wide and Deep Surveys. It catalogues more than 900 million galaxies, more than 60 million quasar candidates and around 15,000 strong gravitational lens candidates, along with spectra from more than 160 million sources. The Wide Survey alone covered about 1,900 square degrees of sky during the period. That area is 14% of the sky Euclid is due to survey over six years, and it works out to almost five per cent of the entire night sky.

Key Facts

The European Space Agency said on November 12 that DR1-Foundation captures the light of more than a billion objects, with the galaxy catalogue alone exceeding 900 million entries. The release combines the Wide Survey, which sweeps large areas quickly, with the Deep Survey, which stares longer at smaller fields to reach fainter objects. Processing was carried out by the Euclid Consortium Science Ground Segment, a collaboration of more than 2,000 scientists, including more than 30 Canadians, according to the University of British Columbia.

Reuters reported on November 12 that the release covered a sky area equal to about 9,500 times the size of the Moon as viewed from Earth, and that it contained 1.7 petabytes, or 1.7 million gigabytes, from roughly 13 months of observations. The wire service, in a story by Will Dunham, noted that the mission's aim is to complete the largest three dimensional atlas of the cosmos ever made, spanning more than a third of the sky, in 2031.

The Guardian reported on November 12 that the data covers about 14% of the total area Euclid will map, and the same figure appears in the official ESA description: 1,900 square degrees out of the roughly 14,000 square degrees planned. The University of British Columbia framed the coverage as almost five per cent of the entire night sky, which counts the same 1,900 square degrees against the full celestial sphere. The two percentages describe one dataset, not a disagreement.

About 15,000 strong gravitational lens candidates are included, a figure that exceeds the total number discovered in the previous half century. Before Euclid, astronomers had less than a thousand confirmed strong lenses, according to Hrishabh Srivastava, a doctoral student in the department of physics and astronomy at the University of British Columbia, who said the odds of finding one had been about one in 10,000. The data release is described in 26 papers submitted to the journal Astronomy and Astrophysics.

Euclid launched in 2023 at a cost of more than $1 billion, according to the University of British Columbia, with the aim of mapping more than one third of the sky. The mission's six year survey is intended to cover that area and to deliver the first dark energy and dark matter results, with the cosmic atlas scheduled for completion in 2031.

Analysis

The lensing catalogue is the most immediately consequential part of the release. Strong lensing occurs when a foreground galaxy's gravity, boosted by its dark matter, bends and magnifies the light of a galaxy behind it into arcs or rings. Because the amount of bending depends on the mass in the foreground, lenses work as scales. Natalie Lines, a doctoral student in astrophysics at the University of Portsmouth and a member of the Euclid Consortium, called gravitational lenses nature's own weighing scales. Going from roughly 1,000 known cases to 15,000 candidates is not a marginal improvement. It turns a collection of curiosities into a statistical sample that can be sliced by mass, distance and environment.

The pipeline behind those candidates is itself a signal of how survey astronomy now works. The University of British Columbia reported on November 12 that the search used machine learning, then thousands of citizen scientists, then expert checks of roughly 6,000 to 10,000 galaxies each, followed by verification with other telescopes. What this really means is that the bottleneck in cosmology has moved from collecting photons to interpreting them. Andy Taylor of the University of Edinburgh, who leads the UK science ground segment, said that no human eyeball is able to look at all of the Euclid data any more, because it is now too big. He also called the result the biggest high resolution image of the universe ever had.

The bigger picture here is that Euclid is not simply amassing photographs. Valeria Pettorino, ESA's Euclid project scientist, said the release marks a major milestone for the mission and for everyone involved, and explained that Euclid measures galaxy distances as a third dimension. That dimension establishes where galaxies sit in space and time across 10 billion years, and it allows the cosmic web to be reconstructed rather than merely pictured. A flat image tells astronomers where objects appear. A three dimensional map tells them how matter clumped, when it clumped, and how quickly that clumping grew.

The 14% figure should temper expectations without diminishing them. This is a foundation release, built to be reused and combined with later data, and its main scientific payoff will arrive once the full survey geometry exists. Even so, the jump in lens numbers alone suggests that the rare has become routine. The Guardian reported that the mission's total haul of probable strong lenses is estimated at 170,000 by the end of the survey, which would make lensing a standard tool rather than a specialist pursuit.

Why It Matters

Dark matter and dark energy together account for about 95% of the universe, as Douglas Scott, a co-author on the lensing work at the University of British Columbia, noted. Everything that telescopes have traditionally studied sits inside the remaining few per cent. A catalogue that maps hundreds of millions of galaxies across most of cosmic history is therefore not just a bigger list. It is the raw material for tests of whether dark energy is a fixed constant or something that changes over time, which is one of the largest open questions in physics.

The release also matters because of who can use it. A survey on this scale produces more data than any single team can examine, and the combination of machine learning, citizen scientists and expert review shows a working model for handling it.

There is a practical edge too. Gravitational lenses magnify distant galaxies that would otherwise be too faint to study, so the 15,000 candidates give astronomers a shortlist of natural telescopes. Euclid has already pinpointed 60 million quasars, some dating to when the universe was just 5% of its current age, with light that set off around 13 billion years ago. Each of those objects is a probe of conditions that no laboratory can reproduce.

Next Up

A further release expected next summer will include results on galaxy distribution and weak gravitational lensing, which together allow a map of where dark matter lies, according to The Guardian. The first dark energy and dark matter results are expected next year, and the full atlas is targeted for 2031. Between now and then, the lens catalogue will grow and the map will fill in.

The near term test is whether the foundation holds up. If the 15,000 candidates survive follow up and the survey statistics behave as expected, Euclid will have converted a promise into a measurement programme. If they do not, the anomaly will still be instructive.