AMHERST, Mass. – The European Space Agency (ESA) and the Euclid Consortium—a collaboration of 2,000 researchers from 300 institutions in 15 European countries, the U.S., Canada and Japan—recently released the first stunning images from the Euclid space telescope, launched in July 2023. Euclid's mission is to 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. The University of Massachusetts Amherst's astronomy department is leading the effort on behalf of the Euclid Consortium to understand the earliest days of the universe, and how we got to where we are today.
For John Weaver, a postdoctoral researcher in astronomy at UMass Amherst and the lead author of one of 10 papers describing Euclid's findings, the satellite is helping him to look at things that shouldn't exist—but do.
"We see galaxies in the nearby universe that have surprisingly large numbers of stars—in fact, they have an uncomfortable number of them, more than we think they should. Where did all these stars come from? Euclid is now showing us superbright galaxies in the early universe less than a billion years after the Big Bang —and they are much brighter than they should be, too. I want to find out if these superbright, very distant galaxies eventually evolve into today's supermassive galaxies."
The light from these galaxies took some 13 billion years to reach us, meaning that we see them as they were in their infancy shortly after their formation. Essentially, Weaver and his colleagues are able to look back in time.
A single Euclid image contains both old supermassive galaxies that have ceased forming their stars and distant young galaxies forming lots of stars. It's like being able to study an ancient fossil and a live dinosaur, all at the same time. "Is it plausible," Weaver wonders, "that these superbright galaxies grow into the supermassive fossils?"
Unprecedented results
The images obtained by Euclid are at least four times sharper than those taken by ground-based telescopes. They cover large patches of sky unrivalled in scale, looking far into the distant universe using both visible and infrared light.
"It's no exaggeration to say that the results we're seeing from Euclid are unprecedented," says ESA Director of Science Carole Mundell. "Euclid's first images, published in November, clearly illustrated the telescope's vast potential to explore the dark universe, and this second batch is no different.
"The beauty of Euclid is that it covers large regions of the sky in great detail and depth and can capture a wide range of different objects all in the same image – from faint to bright, from distant to nearby, from the most massive of galaxy clusters to small planets," Mundell continues. "We get both a very detailed and very wide view all at once. This amazing versatility has resulted in numerous new science results that, when combined with the results from Euclid's surveying over the coming years, will significantly alter our understanding of the universe."
While visually stunning, the images are far more than beautiful snapshots; they reveal new physical properties of the universe thanks to Euclid's unique observing capabilities.
Euclid produced the entire set of Early Release Observations in just a single day, revealing over 11 million objects in visible light and 5 million more in infrared light. Careful measurements of their light has resulted in significant new science.
"Euclid demonstrates European excellence in frontier science and state-of-the-art technology, and showcases the importance of international collaboration," says ESA Director General Josef Aschbacher. "The mission is the result of many years of hard work from scientists, engineers and industry throughout Europe and from members of the Euclid scientific consortium around the world, all brought together by ESA. They can be proud of this achievement – the results are no small feat for such an ambitious mission and such complex fundamental science. Euclid is at the very beginning of its exciting journey to map the structure of the universe."
About the images
Weaver and his colleagues focused on two galaxy clusters, Abell 2390 and Abell 2764.
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.
Euclid's cutout view of Abell 2390 shows the light permeating the cluster from stars that have been ripped away from their parent galaxies and sit in intergalactic space. Viewing this "intracluster light" is a specialty of Euclid, and these stellar orphans may allow us to "see" where dark matter lies.
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 and is approximately 1 billion light years away. 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.
A media kit with images from Weaver's study can be found at this link: https://drive.google.com/drive/folders/14sXrBRJHpFdhmw_FSJDqFdbtAUjfAyDp?usp=sharing
For more on the scientific papers, visit: https://www.cosmos.esa.int/web/euclid/ero-public-release.
All of the new Euclid data, images, and papers can be found here: https://www.cosmos.esa.int/web/euclid/ero-public-release
