Euclid opens 1.7 petabytes on 900 million galaxies—but the dark-energy test waits until 2027

The story

The European Space Agency has opened the first major data release from its Euclid space telescope, delivering 1.7 petabytes—1.7 million gigabytes—from roughly 13 months of observations. DR1-Foundation covers 1,900 square degrees of sky, an area ESA compares with 9,500 full Moons as viewed from Earth. It is the largest step yet toward Euclid’s planned three-dimensional map of the Universe, but it covers only about 14% of the sky area targeted during the six-year survey.

The scale is extraordinary. ESA says the release captures light from more than a billion objects, including over 900 million galaxies. It contains about 15,000 strong gravitational-lens candidates, more than 60 million quasar candidates and spectra for over 160 million sources. Reuters independently confirmed the principal figures and reported that the 15,000 lens candidates exceed the total discovered during the previous half-century.

Those labels matter. A candidate is an object selected by automated analysis, citizen scientists or expert screening for follow-up, not a guaranteed discovery. Confirmation will remove false positives and determine which systems are useful for particular measurements. The release’s value comes from providing a large, consistently observed pool from which statistically robust samples can be built.

Strong gravitational lenses form when the mass of a foreground galaxy or galaxy cluster bends light from a more distant object into arcs, rings or multiple images. Because that bending responds to total mass rather than only visible stars, it can reveal otherwise unseen dark matter around galaxies. Time delays between multiple images of a changing quasar can also help measure cosmic expansion. Euclid turns these previously rare configurations into a catalogue large enough to study as a population.

Spectroscopy supplies another dimension. Euclid splits light into spectra whose features can indicate a galaxy’s distance through redshift. Placing galaxies at measured distances lets researchers reconstruct the cosmic web: the filaments, clusters and voids through which matter is distributed. Comparing that structure at different cosmic ages can test how gravity and the expansion of the Universe have evolved.

The release should not be mistaken for the mission’s final answer on dark energy. DR1-Foundation includes raw data, calibrated images, catalogues and spectra, but the complete DR1 release scheduled for mid-2027 is expected to add higher-level products for galaxy clustering and weak gravitational lensing. Weak lensing measures tiny, statistical distortions across vast numbers of galaxy shapes and is central to mapping dark matter and constraining how cosmic structure grew.

That delay reflects the measurement challenge. Dark-energy conclusions can be distorted by subtle errors in telescope optics, detector response, galaxy-shape measurement, distance estimates or the selection of objects. A catalogue with hundreds of millions of galaxies reduces random uncertainty, but it can amplify systematic bias if calibration is even slightly wrong. More objects are useful only when scientists understand how the instrument and processing pipeline changed their apparent properties.

INNOVOX analysis: the release is a scientific-infrastructure milestone rather than a single discovery. Its importance lies in uniformity, scale and public accessibility. Researchers can now test algorithms, find rare targets and compare measurements across one common survey instead of stitching together observations made by different instruments under different conditions. That shared foundation can accelerate work in galaxy evolution, quasars and clusters even before the principal cosmology products arrive.

The data volume is itself an engineering test. Few research groups can download and locally process 1.7 petabytes. ESA’s Euclid Data Space and complementary archive services therefore become part of the scientific instrument: access controls, computing near the data, metadata quality and reproducible pipelines will shape who can use the release and whether results can be independently checked.

What to watch is the transition from abundance to precision. Researchers must confirm the strong-lens and quasar candidates, validate redshifts and publish independent calibration checks. The mid-2027 DR1 completion should show whether Euclid can translate its remarkable object count into credible measurements of weak lensing, galaxy clustering and cosmic expansion. For now, the mission has delivered the raw scale promised by a survey telescope—not yet the dark-energy verdict built on it.

INNOVOX analysis

Euclid’s immediate innovation is statistical and infrastructural: one instrument has produced a uniformly observed population large enough to turn rare lenses and distant structures into samples rather than anecdotes. The cosmological value will depend on calibration, redshift accuracy and bias control, not catalogue size alone.

What to watch

Watch the mid-2027 complete DR1 release for weak-lensing shear catalogues, galaxy-clustering products and the first dark-energy and dark-matter constraints. Also track confirmation rates for lens and quasar candidates, independent calibration tests and whether researchers can process the 1.7-petabyte archive reproducibly.