The Euclid Consortium releases early scientific papers based on observations made by the Euclid telescope. A number of scientifically exciting targets have been observed and analysed by scientists of the Euclid Collaboration during an Early Release Observations phase, giving a glimpse of the unprecedented power of this telescope meant to provide the most precise map of our Universe over time. The scientific data is accompanied by five new outstanding images as part of Euclid’s Early Release Observations. In addition to these first and promising scientific results, the Consortium also publishes on this day the mission’s reference papers that confirm the outstanding performance of Euclid. The treasure trove comes less than a year after the space telescope’s launch, and roughly six months after it returned its first full-colour images of the cosmos.

“The first Euclid images are astonishing. They demonstrate the huge science potential of Euclid, covering large fields with unprecedented resolution. Although originally thought as a mere showcase of the mission potential, they have led to many interesting scientific results now being published”, says Francisco Castander, Institute of Space Sciences (ICE-CSIC) and Institute of Space Studies of Catalonia (IEEC) researcher.

The full set of early observations targeted 17 astronomical objects, from nearby clouds of gas and dust to distant clusters of galaxies, ahead of Euclid’s main survey. This survey aims to uncover the secrets of the dark cosmos and reveal how and why the Universe looks as it does today.

Unprecedented results

Euclid will trace the hidden web-like foundations of the cosmos, map billions of galaxies across more than one-third of the sky, explore how our Universe formed and evolved over cosmic history, and study the most mysterious of its fundamental components: dark energy and dark matter. Euclid produced this early catalogue in just a single day, revealing over 11 million objects in visible light and 5 million more in infrared light. This catalogue has resulted in significant new science.

While visually stunning, the images are far more than beautiful snapshots; they reveal new physical properties of the Universe thanks to Euclid’s novel and unique observing capabilities. These scientific secrets are detailed further in 10 accompanying papers released by the Euclid collaboration, made available tomorrow on arXiv (linked below), together with five key reference papers about the Euclid mission.

The early findings showcase Euclid’s ability to search star-forming regions for free-floating ‘rogue’ planets just four times the mass of Jupiter; study the outer regions of star clusters in unprecedented detail; and map different star populations to explore how galaxies have evolved over time. They reveal how the space telescope can detect individual star clusters in distant groups and clusters of galaxies; identify a rich harvest of new dwarf galaxies; see the light from stars ripped away from their parent galaxies – and much more.

Among the scientific papers released, there is a strong participation from Spanish institutions and researchers in the Euclid Consortium. In particular, the publication focused on Euclid’s ability to search for star-forming regions for free-floating ‘rogue’ planets has been led by the Instituto de Astrofisica de Canarias (IAC) researcher Eduardo Martín Guerrero de Escalante. This work is a showcase of the power of the Euclid mission to provide the area and depth required to explore the very low-mass population including free floating planets of nearby star-forming regions and very young open clusters.

“Our first paper has focused on developing a method to carefully select new-born free-floating planets down to a few Jupiter masses with Euclid, which is like finding needles in a haystack. Dozens of dark free-floating planets lurk in the Euclid images of the Messier 78 and Horsehead regions, and the challenge is to distinguish them from millions of background stars and extragalactic objects that can display all kinds of colours” says Eduardo Martin Guerrero de Escalante.

José María Diego, researcher at the Institute of Physics of Cantabria (IFCA CSIC-UC), has participated in the study of one of the objects studied by Euclid, the so-called Abel 2390, a gravitational lens or a massive galaxy cluster. In this work, the IFCA CSIC-UC researcher has managed to obtain the first map of the distribution of matter around and in the centre of this cluster (mostly dark matter), which had never been studied in such detail until now.

Another interesting result comes from the study of the intracluster light and intracluster globular clusters of the Perseus cluster. Based on the characteristics of this light, the astronomers involved in the study suggest that the stars have been torn from the outskirts of the galaxies and from the complete disruption of smaller cluster galaxies, dwarf galaxies. Another surprising finding is that these stars, which are expected to orbit the largest galaxy in the cluster, instead orbit a point between the two most luminous galaxies. This novel observation suggests that Perseus may have recently merged with another group of galaxies, causing a gravitational perturbation that led to the observed misalignment. Mireia Montes, IAC researcher involved in the study pinpoints that, “this work was only possible thanks to Euclid’s sensitivity and sharpness”.

Furthermore, the additional five Reference publications provide confirmation of Euclid’s outstanding performance. Among them, the Euclid Flagship simulation, led by ICE-CSIC and IEEC researchers Francisco Castander and Pablo Fosalba, is presented. The Euclid Flagship simulation is a simulated catalogue of billions of galaxies based on the largest cosmological simulation ever conducted, designed to prepare the scientific exploitation for the Euclid mission. The catalogue has been generated using SciPIC, a suite of integrated algorithms within a powerful pipeline dedicated to the generation of massive synthetic galaxy catalogues. The pipeline runs in the Euclid Science Data Center, hosted at the Port d’Informació Científica (PIC), on a high performance big data platform that enables generating a 15 TB catalogue of 5 billion galaxies in 3 hours. Developed to train and validate the ground segment algorithms before the launch, simulations are now used to measure, calibrate and correct systematic biases.

“This is the most detailed and comprehensive simulation of a galaxy survey ever produced. We are very excited to release this mock galaxy catalogue to help exploit the wealth of cosmological information that the survey data will bring,” adds ICE-CSIC and IEEC researcher Pablo Fosalba. Other reference publications provide a summary of the overall Euclid mission and goals as well as describing Euclid’s instruments’ specifications, design, development, and roles within the mission. Performance verification tests of VIS and NISP instruments indicate that both are operating at fully in line with expectations.

¨With just these few magnificent, large field-of-view images at unprecedented resolution, we have already made numerous new findings about the characteristics of our universe. This demonstrates that, after its six years of observation, Euclid will not only help us understand the Dark Universe, but will also leave behind material that will enable future generations of scientists to make wonderful astronomical discoveries,¨ adds Institute of High Energy Physics (IFAE) researcher Cristobal Padilla.

Rafael Toledo, researcher at the Polytechnic University of Cartagena (UPCT) and head of the Infrared Instrument Control Unit (NISP), highlights that ¨the capabilities and reliability of the infrared instrument controlled by the unit responsible for the UPCT are absolutely impressive.¨ Furthermore Spain has a key role in the Euclid Consortium.The Spanish contribution to the payload of the Euclid telescope has been organised around two nodes that joined the scientific consortium in 2010. On the one hand, ICE-CSIC, IFAE, IEEC, PIC, have been responsible for the design, construction, assembly and validation tests of the NISP instrument filter wheel, as well as the cosmological simulations of the mission. On the other hand, UPCT and IAC have been in charge of the electronic unit that controls the NISP instrument and its startup software. Besides, both nodes participate in several teams within the Euclid Science Ground Segment (SGS), responsible for the processing of the telescope data and delivery of the data products to be used for the scientific exploitation. ICE-CSIC leads OU-SIM, the group in charge of image simulations and PIC is the Spanish Science Data Center (SDC-ES) of the mission, taking charge of approximately 5% of the data processing and being the primary datacenter for OU-SIM. Furthermore, in more than 20 Spanish institutions there are around 100 scientists arranging the scientific exploitation of the mission to unravel the mysteries of the dark universe

Euclid new Early Release Observations images

The images obtained by Euclid are at least four times sharper than those we can take from ground-based telescopes. They cover large patches of sky at unrivalled depth, looking far into the distant Universe using both visible and infrared light.

Abell 2390

Euclid’s image of galaxy cluster Abell 2390 reveals more than 50,000 galaxies and shows a beautiful display of gravitational lensing, depicting giant curved arcs on the sky – some of which are actually multiple views of the same distant object. Euclid will use lensing (where the light travelling to us from distant galaxies is bent and distorted by gravity) as a key technique for exploring the dark Universe, indirectly measuring the amount and distribution of dark matter both in galaxy clusters and elsewhere. Euclid scientists are also studying how the masses and numbers of galaxy clusters on the sky have changed over time, revealing more about the history and evolution of the Universe.

IFCA CSIC-UC has contributed significantly to this part of the study, by deriving the first map of the distribution of matter in this cluster using the small distortions, due to gravitational lensing, and combining them with larger distortions, previously measured with the Hubble Space Telescope, in galaxies close to the cluster core.

Messier 78

This breathtaking image features Messier 78, a vibrant star nursery enveloped in interstellar dust. Euclid peered deep into this nursery using its infrared camera, exposing hidden regions of star formation for the first time, mapping its complex filaments of gas and dust in unprecedented detail, and uncovering newly formed stars and planets. Euclid’s instruments can detect objects just a few times the mass of Jupiter, and its infrared ‘eyes’ reveal over 300,000 new objects in this field of view alone. Scientists are using this dataset to study the amount and ratio of stars and smaller (sub-stellar) objects found here – key to understanding the dynamics of how star populations form and change over time.

NGC 6744

In this image Euclid showcases NGC 6744, an archetype of the kind of galaxy currently forming most of the stars in the local Universe. Euclid’s large field-of-view covers the entire galaxy, capturing not only spiral structure on larger scales but also exquisite detail on small spatial scales. This includes feather-like lanes of dust emerging as ‘spurs’ from the spiral arms, shown here with incredible clarity. Scientists are using this dataset to understand how dust and gas are linked to star formation; map how different star populations are distributed throughout galaxies and where stars are currently forming; and unravel the physics behind the structure of spiral galaxies, something that is still not fully understood after decades of study.

Abell 2764 (and bright star)

This view shows the galaxy cluster Abell 2764 (top right), which comprises hundreds of galaxies within a vast halo of dark matter. Euclid captures many objects in this patch of sky, including background galaxies, more distant clusters, and interacting galaxies throwing off streams and shells of stars. This complete view of Abell 2764 and surroundings — obtained thanks to Euclid’s impressively wide field-of-view — allows scientists to ascertain the radius of the cluster and see its outskirts with faraway galaxies still in frame. Euclid’s observations of Abell 2764 are also allowing scientists to further explore galaxies in the distant cosmic dark ages, as with Abell 2390. Also seen here is a very bright foreground star that lies within our own galaxy (V*BP-Phoenicis, a star in the southern hemisphere that’s bright enough to be seen by the human eye). When we look at a star through a telescope, its light is scattered outwards into a diffuse circular halo due to the telescope’s optics. Euclid was designed to make this scatter as small as possible. As a result, the star causes little disturbance, allowing us to capture faint distant galaxies near the line of sight without being blinded by the star’s brightness.

Dorado Group

Here, Euclid captures galaxies evolving and merging ‘in action’ in the Dorado galaxy group, with beautiful tidal tails and shells seen as a result of ongoing interactions. Scientists are using this dataset to study how galaxies evolve, to improve our models of cosmic history and understand how galaxies form within halos of dark matter. This image showcases Euclid’s versatility: a wide array of galaxies is visible here, from very bright to very faint. Thanks to Euclid’s unique combination of large field-of-view, remarkable depth, and high spatial resolution, it can capture tiny (star clusters), wider (galaxy cores) and extended (tidal tails) features all in one frame. Scientists are also seeking distant individual clusters of stars known as globular clusters to trace their galactic history and dynamics.