The European Space Agency (ESA) has released the first large batch of data from its Euclid space telescope, and the Euclid first data release catalogues more than 900 million galaxies. The release, named DR1-Foundation, contains about 13 months of observations. It is the first major data release since Euclid launched in July 2023.
Euclid is on a six-year mission to map about one-third of the sky in three dimensions. ESA says the new data gives researchers the building blocks for the largest 3D map of the cosmos ever made.
A mosaic built from 740 observations
The headline image is a northern-sky mosaic stitched from 740 separate exposures. Together they cover 367 square degrees, and at full resolution the image runs to about 500 gigapixels.
Zoomed in, the mosaic moves from thousands of galaxies to individual systems. Some sit relatively close to Earth, while others emitted their light billions of years ago. Faint background galaxies, which a smaller field of view would miss, add to the detail.
For a closer look at a single spiral galaxy, Subaru Telescope’s detailed view of M77’s galactic loop shows how much structure ground-based observatories can reveal.
The mosaic is part of a wider survey. The two image regions sit inside a footprint of about 1,900 square degrees. ESA compares that area with 9,500 full Moons. The release also includes a separate collection covering 148 square degrees of the southern sky.
Gravitational lenses in unprecedented numbers
The Euclid first data release contains roughly 15,000 strong gravitational lens candidates. Earlier searches had identified only a few hundred such systems over several decades. The source describes it as the largest catalogue of its kind.
A gravitational lens forms when a massive object bends light from a more distant source. A foreground galaxy can stretch the light of a background galaxy into curved arcs, multiple images, or a nearly complete ring. The exact shape depends on how the two galaxies line up and how mass sits in the foreground object.
Lenses also help measure how much mass a galaxy holds. The bending comes from everything in the foreground system, including its stars and dark matter. Researchers study the distortions to estimate that mass.
Quasars and galaxy clusters
The Euclid first data release also lists more than 60 million quasar candidates. Quasars are the bright cores of distant galaxies, where supermassive black holes pull in surrounding gas and dust. That material forms a hot accretion disc and releases large amounts of radiation as it spirals inward.
Some quasars are bright enough to detect across billions of light years. Their light lets astronomers study galaxies from early cosmic history, when the Universe was only about 5 percent of its current age. Euclid has identified candidates from that era.
The survey also captures galaxy clusters. Euclid imaged the Horologium Supercluster, the Messier 81 galaxy group, and the cluster Abell 3128. Abell 3128 is a cluster that holds hundreds of galaxies. The ring galaxy NGC 1291 also appears among the prominent targets.
Euclid also detects intracluster light, a faint glow that fills the space between galaxies in a cluster. This light comes from stars that gravitational interactions have pulled away from their host galaxies. Euclid has detected it in hundreds of clusters, giving researchers material to study how galaxies interact and evolve.
Euclid first data release: measuring distances with spectra
Images show what distant galaxies look like. Spectra help astronomers estimate how far away they are and what they are made of. A spectrum splits light into its component wavelengths, and certain gases leave recognizable markers in that pattern. The Euclid first data release, DR1-Foundation, includes spectra from more than 160 million sources.
The spacecraft carries a 1.2-metre telescope and two scientific instruments. The Visible Instrument (VIS) uses 36 CCD detectors to produce images with about 600 megapixels. The Near-Infrared Spectrometer and Photometer (NISP) records near-infrared light and gathers additional data on each source.
Robotic cameras on other worlds document unfamiliar landscapes in similar detail. Curiosity rover’s panorama of Mars’ yardang layer offers a useful comparison for how spacecraft imaging captures terrain.
Aiming at dark matter and dark energy
ESA says the mission aims to shed light on two of the biggest questions in cosmology: dark energy and dark matter. Dark matter emits no detectable light, yet its gravity shapes how galaxies form and cluster.
Euclid will map the cosmic web, the long filaments of galaxies and clusters separated by sparse regions. Tracing that structure across different distances should show how the Universe developed over billions of years.
Dark energy describes the unknown influence behind the accelerating expansion of the Universe. Euclid will measure galaxy distances and track the growth of cosmic structures. Those measurements will provide evidence for testing competing explanations.
Release timing differs between sources. The main article says ESA expects the complete Data Release 1 in mid-2027. That release will add weak gravitational lensing measurements and more information about galaxy clusters.
What the mission team says
“These are far more than beautiful pictures; today marks a scientific milestone in our study of the cosmos,” she said. She added that the release demonstrates the excellence of European technology, science and international collaboration.
“We’re now releasing more than a year of data covering a significantly larger area. This unlocks ground-breaking science.”
The Euclid first data release gives astronomers more sky, more galaxies and more lenses than any single team can review by hand. The next releases will show which of these objects change what researchers understand about the dark Universe.
Frequently asked questions
How many galaxies does Euclid’s first data release catalogue include?
The Euclid first data release, named DR1-Foundation, catalogues more than 900 million galaxies. It contains about 13 months of observations and is the first major data release since Euclid launched in July 2023.
How many gravitational lens candidates are in the Euclid data release?
The release contains roughly 15,000 strong gravitational lens candidates. Earlier searches had identified only a few hundred such systems over several decades.
What is Euclid’s mission and how long will it last?
Euclid is on a six-year mission to map about one-third of the sky in three dimensions. The data gives researchers the building blocks for what ESA says will be the largest 3D map of the cosmos ever made.
How many quasar candidates does the Euclid data release list?
The Euclid first data release lists more than 60 million quasar candidates. Quasars are the bright cores of distant galaxies, where supermassive black holes pull in surrounding gas and dust.
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