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Euclid telescope sends back first images from ‘dark universe’ mission

Perseus cluster and Horsehead nebula captured in dazzling detail as part of effort to create cosmic 3D map

Hannah Devlin Science correspondent

@hannahdev

Tue 7 Nov 2023 14.25 GMT

The Euclid space telescope has beamed back its first images in a mission that promises to lift a veil on the “dark universe”.

The €1bn (£850m) European Space Agency (Esa) mission is focused on dark matter and dark energy, which together make up 95% of the universe but their natures are almost entirely mysterious. The first images show the Perseus galaxy cluster and Horsehead nebula in dazzling detail and capture approximately 100,000 galaxies in a single snapshot, showcasing the telescope’s unmatched ability to make razor-sharp observations across a vast expanse of space.

Ultimately the telescope, which can detect galaxies out to 10bn light years, is aiming to create the largest cosmic 3D map ever made. This will allow astronomers to infer the large-scale distribution of dark matter and reveal the influence of dark energy in the early universe. Dark matter pervades the universe and acts as a cosmic glue that holds galaxies together, while dark energy is the name given to an enigmatic force that is thought to be accelerating the expansion of the universe.

Prof Carole Mundell, the Esa’s director of science, said the mission, which launched in July, would push the frontiers of scientific knowledge into uncharted territory “beyond Einstein”.

Galaxies belonging to the Perseus cluster

Galaxies belonging to the Perseus cluster. Photograph: Esa/Euclid/Euclid Consortium/NAS/AFP/Getty Images

“As humans, we’ve managed to figure out how 5% of the universe works and we’ve also figured out that there’s another 95% that remains unknown to us,” she said. “We can’t travel out to the edge of the universe to investigate, but we’re bringing those images back to Earth and studying them on computers – and for only €1.4bn. I think it’s magical.”

Over the next six years, Euclid will observe about 8bn galaxies using infrared and visible light across 36% of the night sky. In some cases, light from these distant bodies will pass close to dark matter on its journey towards Earth. When that happens, its gravitational field will bend the path of the light, making the galaxies appear distorted in the final image.

“A background round galaxy might be changed into a banana shape,” said Prof Mark Cropper of University College London, who led on designing Euclid’s optical camera. By analysing the patterns of distortion, astronomers could infer a map of dark matter distribution across the night sky and over the history of the universe. “You do it like toast in a toast rack,” Cropper said. “First you look at the distortion of the nearby galaxies and work out the dark matter in the first slice of toast. Then you go further back to the next slice – further and further away in the universe and back in time.”

The spiral galaxy IC 342.

The spiral galaxy IC 342. Photograph: Esa/Euclid/Euclid Consortium/NAS/AFP/Getty Images

The mission may not initially answer what dark matter is, but should at least reveal where it is and how it behaves.

Researchers will also observe the motion of galaxies to build a precise picture of the competing forces of gravity, which cause galaxies to clump together, and dark energy, which is driving the accelerated expansion of space. This will allow scientists to see, for the first time, how dark energy was at work in the early universe.

Mundell said: “Dark matter pulls galaxies together and causes them to spin more rapidly than visible matter alone can account for; dark energy is driving the accelerated expansion of the universe. Euclid will for the first time allow cosmologists to study these competing dark mysteries together.”

René Laureijs, the Esa’s Euclid project scientist, added: “We have never seen astronomical images like this before, containing so much detail. They are even more beautiful and sharp than we could have hoped for, showing us many previously unseen features in well-known areas of the nearby universe. Now we are ready to observe billions of galaxies, and study their evolution over cosmic time.”