Euclid Releases Billion-Object Foundation for Cosmic Map

The European Space Agency released DR1-Foundation on Wednesday, November 12, the first major batch of data from its Euclid space telescope. The release captures the light of more than a billion objects over an area of sky as big as 9,500 full Moons. It isn't a finished map. It's the surveyed ground the map will stand on.

The counts inside the release are the story. More than 900 million of the cataloged objects are galaxies, sorted by Euclid's analysis pipeline from about 13 months of observations gathered between spring 2024 and spring 2025. The Wide Survey covers 1,900 square degrees. The full release holds spectra, the split-out light that gives a galaxy's distance, for more than 160 million sources, plus about 60 million quasar candidates.

The whole package runs to about 1.7 million gigabytes of data, drawn from more than 120,000 calibrated frames from Euclid's two instruments: the VIS visible-light camera, a 600-megapixel imager, and the NISP near-infrared spectrometer and photometer. Carole Mundell, ESA's director of science, called it the largest space-based survey of its kind. The data are public through the Euclid Data Space platform, so any research group can work from the same catalog.

One haul stands out on its own. Euclid found about 15,000 strong gravitational lens candidates, cases where a foreground galaxy's gravity bends the light of a galaxy behind it into arcs and rings. ESA says it's the largest strong lens catalog ever assembled, bigger than all previous catalogs combined, and it includes rare setups that used to surface one at a time: compound lenses, lenses made by spiral galaxies, and lensed quasars.

What the release doesn't do is just as clear. Euclid launched on July 1, 2023, to measure how the universe's expansion has changed over time, and that measurement is the mission's test of dark energy and dark matter. The cosmology-grade products, including the weak lensing analysis that tracks how mass distorts galaxy shapes, aren't in this batch. ESA and the Euclid Consortium held them for the full DR1, scheduled for June 16, 2027.

The 1,900 square degrees are also only about 14 percent of the sky area Euclid will cover in its six-year survey. The foundation released this week won't be redistributed in 2027. The later release adds the higher-level analysis on top of it. For now, the working universe got a billion new entries, and the map they belong to is still being drawn.

Euclid's design explains the volume. The telescope sits at the L2 Lagrange point, about 1.5 million kilometers from Earth, and scans the sky in wide steps rather than pointing at single targets. Its near-infrared instrument lets it peer through the dust of our own galaxy, which is how it captured galaxies like IC 342, the Hidden Galaxy, that visible-light surveys struggle to see. Every step adds thousands of galaxies to the catalog at once.

The accompanying science papers are preprints for now, posted ahead of peer review, and astronomers outside the consortium get the same public data at the same time. That open structure is part of the point. A catalog this size isn't one team's result. It's shared infrastructure, and the discoveries it produces over the next two years will arrive paper by paper, each one standing on the foundation released this week.