Explained: More stunning images from Euclid telescope released by the ESA


Euclid, stylised by the European Space Agency (ESA) as their ‘dark Universe detective’, is a space-based telescope on a six-year mission to explore how the Universe has expanded and structure has formed over cosmic time, unravelling the mysteries of dark energy and dark matter.

Five breathtaking images were released in May by ESA scientists, capturing both the visual beauty of the Universe and some of its key physics. They are some of the largest images of the Universe ever taken from space. Equipped with instruments that operate at visible and near infrared wavelengths, Euclid’s ‘eyes’ are looking deep into the cosmos. These images accompanied new research described in the first set of “Early Release Observation” (ERO) papers from the mission.

These are some of the largest images of the Universe ever taken from space

Dr Valeria Pettorino is one of ESA’s Euclid Project Scientists. “Euclid is a unique, ground-breaking mission, and these are the first datasets to be made public – it’s an important milestone,” said Pettorino. “The images and associated science findings are impressively diverse in terms of the objects and distances observed. They include a variety of science applications, and yet represent a mere 24 hours of observations. They give just a hint of what Euclid can do. We are looking forward to six more years of data to come!”

Prof. Richard Massey, of Durham University’s Centre for Extragalactic Astronomy, is a founder of the Euclid mission and has been developing its design and science goals for 20 years. “[These] images show the capacity Euclid has to see structures and objects in the dark Universe in detail that we have never seen before. This is a hugely exciting time, which will significantly advance our knowledge and understanding of the evolution of our Universe,” said Massey in a press release from the University.

Other members of the Euclid Consortium – which consists of over 2600 members from 300 institutes in 15 European countries plus the United States, Canada, and Japan – who are based in Durham include Prof. Carlton Baugh and Prof. Mathilde Jauzac of the Institute of Computational Cosmology.

Euclid’s main survey will produce a 3D cosmic map of billions of galaxies in an ambitious attempt to shed light on what roles dark matter and energy play in shaping the Universe. “Scientists are using what they can see in the light to try to trace what we cannot see in the dark,” said Carole Mundell, ESA’s Director of Science. “This actually gives me goosebumps when I think about the power of Euclid to really unveil the hidden cosmos.”

The ERO results are the first released for the Euclid mission and consist of remarkable discoveries obtained from observations of 17 different astronomical targets. Two of these targets were Messier 78 and Abell 2390.

The scientific results are the first released for the Euclid mission

Messier 78 is the closest of these targets to Earth, at around 1600 light years away. Euclid has revealed hidden regions of star formation in this stellar nursery, previously cloaked by interstellar dust. ESA stated “this image is unprecedented – it is the first shot of this young star-forming region at this width and depth.” An undoubtedly stunning image, it is for reasons far beyond just its looks; scientists are exploring the data further and using it to study the number of stars and even smaller objects in this region. This is crucial to understanding how populations of stars form and change over time.

Abell 2390 is the furthest of these targets, at 2.7 billion light years away. This is a galaxy cluster containing more than 50,000 galaxies. Light travelling to us from distant galaxies behind this cluster is bent by gravity, revealing itself as a stunning display of curved arcs on the image – this is called gravitational lensing. Scientists can use this data to measure the amount and distribution of dark matter in galaxy clusters like this one. 

Several other key targets include the Dorado group – a group of galaxies which are being studied to see how galaxies form in so-called ‘haloes’ of dark matter and how they evolve over time – and NGC 6744, a spiral star-forming galaxy which Euclid covers in its entirety.  

Another of this mission’s Project Scientists, René Laureijs, said of the first Euclid images: “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.”

Image: Messier 78, Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi

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