Euclid First Data Release Maps More Than a Billion Cosmic Objects

The European Space Agency's Euclid space telescope has released its first major batch of science data, and the numbers are enormous. Published on 12 November 2026 under the name DR1-Foundation, the release captures the light of more than a billion objects across an area of sky as big as 9,500 full Moons. ESA calls it the foundation for the best-ever 3D map of the Universe.

This Euclid first data release is the first large release of regular survey data since the telescope launched in mid-2023. Earlier releases were small samples meant to show what the mission could do. This one is a real working dataset, open to every scientist in the world, and it covers about 14 percent of the sky Euclid is set to map over its six-year survey.

What is in the release

DR1-Foundation is built from about 13 months of observations, taken between spring 2024 and spring 2025. In that time Euclid's Wide Survey covered around 1,900 square degrees of sky, and its Deep Survey stared longer at a few smaller patches. According to the official DR1 overview, the release includes:

• more than 900 million galaxies;
• around 15,000 candidate strong gravitational lenses;
• more than 60 million candidate quasars, the blazing cores of distant galaxies;
• spectra for more than 160 million sources;
• about 1.7 million gigabytes of data in total.

That last figure is worth pausing on. 1.7 million gigabytes is roughly 1.7 petabytes, more than most universities could store on their own servers. To make it usable, ESA has put the data on its Euclid Data Space platform, where researchers can explore and analyse it online rather than download everything.

Why Euclid exists: the dark Universe

Everything we can see, from stars and planets to gas and dust, makes up only about 5 percent of the Universe. The rest is dark matter, which we detect only through its gravity, and dark energy, the mysterious something that is making the expansion of the Universe speed up. Euclid was built to study both, which is why ESA often calls it its "dark Universe detective".

It does this in two ways. First, it measures the shapes of billions of galaxies. Light from distant galaxies is bent slightly by the gravity of matter it passes on its way to us, an effect called weak gravitational lensing. By measuring tiny, shared distortions across huge areas, scientists can map where the invisible dark matter sits. Second, Euclid measures how far away galaxies are, using their spectra, and so builds a 3D picture of how galaxies cluster. How that clustering changes over cosmic time reveals how dark energy has shaped the Universe.

For a sense of the distances involved, the light from many of these galaxies left them billions of years ago. Our light-travel time calculator and astronomy distance converter help turn those numbers into something easier to picture.

Fifteen thousand cosmic magnifying glasses

One of the most eye-catching parts of the release is the list of about 15,000 strong lens candidates. In a strong lens, a massive galaxy or cluster sits almost exactly in front of a more distant galaxy and bends its light into arcs, multiple images or even a complete ring, known as an Einstein ring. Before Euclid, astronomers knew of only a few thousand such systems in total.

Strong lenses are useful for two reasons. They act as natural magnifying glasses, letting telescopes see galaxies that would otherwise be too faint. They also weigh the lensing galaxy, including its dark matter. NASA's Hubble has just published its own gallery of lenses to prepare for the Nancy Grace Roman Space Telescope, which will hunt for many more. You can follow Roman's progress on our Roman Space Telescope tracker.

The quasar candidates are a treasure of their own. Quasars are powered by gas falling into supermassive black holes, and they shine so brightly that they can be seen across most of the observable Universe. With more than 60 million candidates, astronomers can study how giant black holes grew over cosmic time and use quasar light as a backlight to probe the gas between galaxies.

Where Euclid works

Euclid orbits around the Sun-Earth L2 point, about 1.5 million km from Earth on the side away from the Sun, the same region used by the James Webb Space Telescope. From there it has a stable, cold view of the sky and can point away from the Sun, Earth and Moon. Our explainer on why JWST orbits L2 covers the same advantages that apply to Euclid.

Euclid and Webb do very different jobs, though. Webb looks very deeply at small patches of sky, while Euclid sweeps across huge areas with a wide-field camera of about 600 megapixels and a near-infrared instrument. The two complement each other: Euclid finds rare and interesting objects, and Webb or Hubble zoom in on them. Our comparison of Hubble vs James Webb explains how those older telescopes split their work.

What comes next

DR1-Foundation is the first of two steps. The full DR1, due in mid-2027, will add the higher-level products that cosmologists need for weak lensing and galaxy clustering studies, and it will support the mission's first big measurements of dark matter and dark energy. Further releases are planned for March 2029 (DR2) and October 2031 (DR3), each covering more of the sky.

The data is also being opened up for discovery hunts. ESA is running a Euclid hackathon from 23 to 26 November 2026, where teams will compete to find the rarest objects in the release, from strange galaxy shapes to collisional ring galaxies. Ring galaxies have been in the news before: Webb recently found the most distant ring galaxy yet, and Euclid's huge sky coverage should turn up many nearer examples.

For now, the Euclid first data release gives astronomers a billion new objects to study and a first real taste of the 3D map still to come. If you want to see some of the galaxies Euclid studies with your own eyes, our guide to deep-sky objects tonight shows which galaxies and clusters are well placed from your location.