On Thursday (23 May), the European Space Agency (ESA) and its collaborators released a set of five images constructed by its ground-breaking Euclid Space Telescope. The Euclid consortium previously released five images from the space telescope on November 7, 2023.
Euclid has been called Europa’s “dark universe detective” because its wide field of view allows it to track billions of galaxies over 10 billion years of cosmic history, giving astronomers tools that can reveal more about two mysterious elements of our cosmos: dark energy and dark matter.
Even before he set about gathering scientific data to unravel the mysteries of dark energy and dark matter, collectively called the “dark universe,” Euclid demonstrated his potential with these two amazing sets of images.
As such, Space.com asked several scientists in various fields to explain which of Euclid’s images from the two publications are their favorites so far and why.
Connected: The ‘dark universe detective’ Euclid telescope has revealed new images of space – and they’re remarkable
But first, dark universe 101
Dark energy is the alternate name given to the force accelerating the expansion of the universe, pushing galaxies apart faster and faster. Looking at galaxies that existed when the 13.8-billion-year-old universe was only about 4 billion years old could reveal how this force has evolved over time, helping to determine its true nature.
Dark matter, on the other hand, is a form in the universe that is virtually invisible because it does not interact with light. This means that it cannot be made up of the particles that make up “ordinary” matter. However, since there is a gravitational influence, dark matter halos have influenced the development of the largest structures in the universe. Euclid’s field of view is wide enough to capture these structures in a single image, meaning it could help make the case for how dark matter has affected galactic evolution.
Dark energy accounts for about 67% of the energy and matter budget of the Universe, while dark matter accounts for about 27%. This means that the “dark universe” collectively accounts for about 95% of the contents of the universe, with stars, planets, the moon, people, cats and the rest of the everyday “things” we understand (maybe not cats to be fair) taken into account for only 5% of the universe. This makes the “dark universe” a big problem, to put it mildly.
Euclid takes a walk on the dark side
Luz Ángela García Peñaloza is a cosmologist at Universidad ECCI in Colombia who studies the mystery of dark energy and its influence on cosmic evolution. This means that she watched Euclid’s development with great interest.
“Euclid observed the universe in a completely new way, and this will generate a gigantic census of galaxies. Personally, I find it fascinating how beautiful these first pictures look, and all the incredible information they will reveal,” García Peñaloza told Space.com. “I had to take a deep breath when I saw the images because of their beauty and high resolution.”
When asked to choose her favorite image from the Euclid editions, Garcia Penaloza chose one from the galaxy cluster Abell 2390 (below).
“It’s just breathtaking,” she said. “Any image that reveals information about the distribution of galaxies in the large-scale structure of the universe will provide a handful of information about the nature of the ‘dark side’ of the cosmos.”
Italian astrophysicist Andrea Botteon of the Istituto di Radioastronomia: IRA (INAF-IRA) also chose the Abell 2390 image as his favorite of the new Euclid set.
“As an astrophysicist working on galaxy clusters, I can tell you that my favorite new release is the image of Abell 2390,” Boteon said. “Along with the previously published image of the Perseus cluster [below]this demonstrates the ability of Euclid to recover the very low surface brightness emission from galaxies and especially the cluster light!”
Amateur astronomer Giuseppe Donatiello has discovered 11 galaxies in astronomical survey data, nine of which are named after him, cementing his place in astronomy textbooks. He explained that each expert will choose a different image from Euclid as a favorite based on their area of study. It definitely has a top pick and it comes from the November 2023 batch of images from Euclid.
“As a fan of the Local Group and dwarf galaxies in the local universe, I was impressed by the detail in NGC 6822,” Donatiello told Space.com. “I have looked at images of this galaxy taken with all the most powerful ground-based instruments, but the detail and depth of Euclid is at a much higher level. Clusters, nebulae and [globular clusters] are easily recognizable in Euclid’s image instead of blurred details. I was lost in that field of view for hours!”
Donatiello also chose his favorite image from recent editions of Euclid.
“Of the new ones, the most interesting to me is NGC 6744 because of the fine detail in the galaxy’s spiral arms,” Donatiello continued. “I also deal with star streams [stars and gas pulled from their galaxies by tidal forces], and the Euclid images contain stellar flux information that I just can’t get in lower resolution images. I hope the first public release of data [DR1] from Euclid is as usable as data from other deep surveys.
“If so, I’ll have fun!”
David Kipping is an assistant professor of astronomy at Columbia University who studies the existence of moons around planets outside the solar system. He also chose an image from the previous edition as his favorite Euclid painting to date.
“These are wonderful images that really show off the impressive field of view. The Horsehead Nebula has to be my favorite!” Kipping told Space.com. “Of course, these images are primarily for public use, not science, so I look forward to seeing the early scientific results.”
This new set of images and the previous set are part of Euclid’s Early Release Observations and were collected before February 14, 2023, when the space telescope began its main science operations. Thus, both sets of spectacular images represent only a small fraction of the observations that the telescope will make over the next six years during its main mission.
Garcia Peñaloza said that while these new images and the previous set show that Euclid lives up to expectations, the space telescope still has a lot to offer.
“This is just the beginning of what we will be able to see during Euclid’s life,” García Peñaloza concluded. “I am sure that Euclid will shed light on our understanding of many cosmic mysteries. The best is yet to come from Euclid!”