In March 2025, ESA and the EC released the first 63 square degrees of calibrated Euclid science images and catalogues, a set of descriptive technical articles and first scientific papers to the public. The Q1 data set demonstrated the unprecedented power of the Euclid telescope designed to provide the most precise map of our Universe over time. Now, a second set of publications became ready and is available on the arXiv preprint server.
Scientific results released 5 November 2025
This new series of seven articles using the Euclid Q1 dataset provides a panoramic view of galaxy formation and evolution across cosmic time.
- At the earliest epochs, the paper led by Natalie Allen reveals the discovery of two ultra-bright galaxies at redshift z > 8, among the more than 100,000 Lyman Break Galaxies expected at z = 6–12, tracing the emergence of the first stellar systems in the infant Universe.
- Building on these distant beacons, Lorenzo Bazzanini et al. introduce ARTEMIDE, an open-source deep-learning algorithm that automatically detects gravitational arcs, offering a powerful new tool to identify strong lensing systems and probe mass distributions in galaxies and clusters – key processes in their growth.
- Maximilian Fabricius et al. explore the later stages of galactic evolution, focusing on mergers that produce supermassive black hole binaries and depleted stellar cores. Their identification of 666 candidate systems with secondary nuclei in early-type galaxies provides crucial insight into how galaxies coalesce and reshape their central structures.
- Moving to population-scale evolution, the paper led by Fabrizio Gentile analyses nearly one million galaxies and find that morphology and star formation are tightly linked to environment: in low-density regions, galaxies evolve internally into star-forming bulge-dominated systems before quenching, while in dense environments, star formation ceases first, leading to quiescent disc galaxies that later transform into spheroids.
- Complementing this, Ryley Hill and collaborators show from over two million star-forming galaxies that dust-to-stellar mass ratios have steadily declined since z ≈ 1, marking a gradual depletion of the material needed for star formation.
- Manuela Magliochetti et al. investigate radio emission as a tracer of galactic nuclear activity, finding that radio-loud AGN preferentially reside in merging systems, whereas radio-emitting star-forming galaxies tend to be isolated – highlighting the dual pathways of galaxy growth through both mergers and secular processes.
- Finally, the team led by Daniela Vergani et al. identifies a rare population of 65 galaxies exhibiting highly ionised emission lines, signatures of extreme astrophysical phenomena such as active galactic nuclei, shock fronts, or Wolf–Rayet stars, offering a new window into energetic feedback mechanisms shaping galaxy evolution.
These studies demonstrate Euclid’s unique power to connect the earliest luminous sources with the complex physical processes – mergers, feedback, and environmental effects – that have sculpted the rich diversity of galaxies observed in today’s Universe. Together with the initial set of 35 publications on the Q1 dataset, the papers will be published in a special issue of the journal Astronomy & Astrophysics once the formal reviewing process by the journal is concluded.
The Euclid Publication Process
Coordinating the publications of a consortium as large as Euclid, accounting for the authorship rights of many hundreds of consortium members, and maintaining a constantly high quality standard for all publications is a complex task. Central to this task is the EC’s editorial board (ECEB). All publications by the EC are first seen by the ECEB, which is chaired by Peter Schneider at the Argelander Institute for Astronomy (AIfA) in Bonn and John Peacock in Edinburgh.
Before being submitted to a journal, EC publications then undergo a thorough internal processing and reviewing. This also ensures that all scientists in the consortium have a chance to get involved in the writing of these papers. The office of the ECEB, located at the AIfA in Bonn and maintained by Patrick Simon, deals with all the technical and administrative aspects of the board’s daily business and extensive communication with the authors.
Background
The ‘Q1’ data set released 19 March 2025
The Q1 data unveiled on 19 March 2025 provide a first glimpse of Euclid’s cosmological survey. These fields are illustrative of what will be extensively analysed by scientists within the Euclid Collaboration to map the large-scale structure of the Universe across cosmic time, and investigate the nature of dark matter and dark energy in the years to come. With a sky area of about 63 square degrees, the Q1 release is seven times larger than the earlier ERO release, and represents the largest contiguous areas of sky ever observed with an optical/near-infrared space telescope. The Q1 data are complemented by observations of a star-forming region in our own galaxy, taken early-on in the mission to test and improve Euclid’s guiding performance.
Thanks to Euclid’s very wide field of view and high resolution, these exquisite data are also highly valuable for various astrophysical studies on smaller scales, ranging from clusters of galaxies to planet-sized objects. All the papers published today are dedicated to this non-cosmological science, also called legacy science.
The Euclid Mission
Euclid is a satellite mission which aims at mapping the darkest regions of the sky over a period of six years. The extensive data are expected to give astronomers new insights into the nature of dark energy and dark matter. The telescope was launched on July 1st, 2023, and started its regular science observations on February 14th, 2024, after a commissioning phase of a bit more than half a year.
The Euclid Consortium (EC) is, together with the European Space Agency (ESA), responsible for the planning, the construction, and the operation of the Euclid space telescope. The EC assembles more than 2600 members. Among these are more than 1000 active scientist from more than 300 research institutes in 15 European countries, the United States of America, Canada and Japan.
Euclid is funded by ESA, with national contributions by the German Federal Ministry of Research, Technology, and Space through the German space agency, DLR.
Future milestones for the Euclid mission
The next data release from the Euclid Consortium will concern Euclid’s nominal survey and core-science, including results about the nature of dark energy. A first worldwide data release is currently planned for October 2026. At least two other quick releases and two other data releases are expected before 2031, the currently foreseen end date of Euclid’s main survey.