Archive for the Euclid Category

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Euclid Space Warps – help the hunt for galaxy-galaxy lenses!

Posted in Euclid, The Universe and Stuff with tags , , , on April 21, 2026 by telescoper
A collage of fourteen by eight squares containing examples of gravitational lenses. Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by M. Walmsley, M. Huertas-Company, J.-C. Cuillandre.

I’m sharing the text of a press release from Euclid here to encourage readers to join in this new Zooniverse project.

–o–

In brief

With the launch of Space Warps, a new citizen science project on the Zooniverse platform, you can now join in the search to find rare and elusive strong gravitational lenses in never-before-seen images captured by the European Space Agency’s Euclid space telescope. The project aims at shining a light on dark matter in galaxies and providing clues about mysterious dark energy.

In-depth

Warps in spacetime do not only show up in science fiction movies like Interstellar. In real life, we can see the warping effect that gravity has on spacetime in the form of gravitational lensing.

The enormous gravity of a massive object – such as a galaxy or cluster of galaxies – distorts the shape of spacetime and can bend the light rays coming from a distant galaxy behind. By warping spacetime, the foreground galaxy acts like a magnifying glass.

Light from the background object that would be obscured doesn’t travel in a straight line anymore. Instead, it curves around the intervening mass, often producing multiple images, stretched arcs, or even a complete ring known as ‘Einstein ring’, like the one recently discovered by Euclid.

Strong gravitational lenses offer a striking demonstration of Einstein’s theory of general relativity, showing that matter in the Universe can act as a natural telescope, bringing distant objects into sight.

ESA’s Euclid telescope is revolutionising the studies of strong gravitational lensing by providing very sensitive imaging over large swaths of the sky in unprecedented detail. This is exactly what is needed to identify rare gravitational lenses.

In March 2025, 500 galaxy-galaxy strong lenses were found nestled in just the first 0.04% of Euclid data, most of them previously unknown. This pioneering catalogue was created thanks to the combined effort from citizen scientists, artificial intelligence (AI) and researchers.

Early glimpse of new Euclid images

As Euclid continues its survey, sending around 100 GB of data back to Earth every day, ESA and the Euclid Consortium once again need help from citizen scientists to identify strong gravitational lenses in a large data set.

For this, the Space Warps team has launched a citizen science project based on new Euclid images, which will be part of the future Euclid Data Release 1. While this data is not public yet, by participating in this new citizen science project you can get an early glimpse of these new images of galaxies captured by the telescope.

For this project, you will be inspecting new high quality imaging data from Euclid in which many previously unknown strong lenses are hiding. About three hundred thousand images pre-selected by AI algorithms will be shown, which are fine-tuned with the results from the initial citizen-science Euclid strong lens search. These are the highest ranked candidates from a whopping 72 million galaxies from DR1 that were classified by the AI algorithms. Scientists expect that this exquisite high-quality data will reveal more than 10 000 new lenses.

What can we learn from strong lenses

The Euclid mission explores how the Universe has expanded and how its structure has changed through cosmic history using mainly two methods: weak lensing and baryonic acoustic oscillations. From this, scientists can learn more about the role of gravity and the nature of dark matter and dark energy.

Strong gravitational lenses can also provide insights into these central questions. For example, strong lensing features can ‘weigh’ individual galaxies and clusters of galaxies. This reveals the total matter (whether dark or light) and traces the distribution of dark matter. By studying strong lenses across cosmic time, scientists can trace the expansion of the Universe and its apparent acceleration. This will provide additional insight into the role of dark energy.

“We’ve already seen the success of combining AI with visual inspection by citizen volunteers and scientists on Space Warps, efficiently finding hundreds of high‑probability lens candidates in an initial small Euclid search in 2024”, explains Aprajita Verma, Space Warps’ co-founder and project lead at the University of Oxford, UK.
“In this brand new DR1 data, 30 times larger than the initial search and together with our improved AI algorithms, we are expecting to find more than 10 000 high quality lens candidates. This is more than four times the number of lenses than we have been able to find since the first gravitational lens was discovered nearly 50 years ago.”

This step-change is possible thanks to Euclid. The mission can map large areas of the sky with unique sharpness, an ideal combination for finding rare objects like strong gravitational lenses.

“We can’t wait to see what we will find within this unprecedented dataset. Join us on Space Warps to take part in this exciting search!” concludes Aprajita.

About Euclid
Euclid was launched in July 2023 and started its routine science observations on 14 February 2024. The goal of the mission is to reveal the hidden influence of dark matter and dark energy on the visible Universe. Over a period of six years, Euclid will observe the shapes, distances and motions of billions of galaxies out to 10 billion light-years.

Euclid is a European mission, built and operated by ESA, with contributions from NASA. The Euclid Consortium – consisting of more than 2000 scientist from 300 institutes in 15 European countries, the USA, Canada, and Japan – is responsible for providing the scientific instruments and scientific data analysis. ESA selected Thales Alenia Space as prime contractor for the construction of the satellite and its service module, with Airbus Defence and Space chosen to develop the payload module, including the telescope. NASA provided the detectors of the Near-Infrared Spectrometer and Photometer, NISP. Euclid is a medium-class mission in ESA’s Cosmic Vision Programme.

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The Perseus Cluster

Posted in Euclid, Maynooth, The Universe and Stuff with tags , , , , on April 16, 2026 by telescoper

In a vain attempt to convince my readership that I know anything about observational astronomy, I thought I’d share this image of the central regions of the Perseus Cluster (also known as Abell 426) made by my final-year project students:

Picture Credit: Ben Doyle

The image was taken last November using the 1.20m reflecting telescope at the Observatoire de Haute-Provence where the final-year astrophysics students from Maynooth spent a week last November on a field trip taking various observations. The exposure was 240 seconds and the field of view is about 15 arcminutes on a side. Most of the objects in the image are galaxies, rather than stars.

I asked my students to look at this cluster (which is about 10 degrees across), partly because it appears near the Zenith in November so would be a good target, partly because it is nearby so the galaxies in it are therefore quite bright, and partly because it was observed by Euclid and featured among the Early Release Observations. The Euclid telescope is also 1.20m in diameter, but because it has a very fancy camera and is in space, Euclid reveals far more galaxies but I was nevertheless impressed at how well this turned out!

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Hubble, Euclid and the Cat’s-Eye Nebula

Posted in Euclid, Maynooth, The Universe and Stuff with tags , , , , , on March 3, 2026 by telescoper

It’s been a while since I posted any Euclid-related news so I’m taking this opportunity to share a press-release related to this image:

ESA/Hubble & NASA, ESA Euclid/Euclid Consortium/NASA/Q1-2025, J.-C. Cuillandre & E. Bertin (CEA Paris-Saclay), Z. Tsvetanov

The Press Release follows:

–o–

For this ESA/Hubble Picture of the Month, Hubble  is joined by ESA’s Euclid to create a new view of the most visually intricate remnants of a dying star: the Cat’s Eye Nebula, also known as NGC 6543.

This extraordinary planetary nebula in the constellation Draco has captivated astronomers for decades with its elaborate and multilayered structure. Observations with ESA’s Gaia mission place the nebula at a distance of about 4300 light-years.

Planetary nebulae, so-called because of their round shape when viewed through early telescopes, are in fact expanding gas thrown off by stars in their final stages of evolution. It was the Cat’s Eye Nebula itself where this fact was first discovered in 1864 – examining the spectrum of its light reveals the emission from individual molecules that’s characteristic of a gas, distinguishing planetary nebulae from stars and galaxies. 

Here, the nebula is showcased through the combined eyes of the NASA/ESA Hubble Space Telescope and ESA’s Euclid, highlighting the remarkable complexity of stellar death.

Though primarily designed to map the distant Universe, Euclid captures the Cat’s Eye Nebula as part of its deep imaging surveys. In Euclid’s wide, near-infrared and visible light view, the arcs and filaments of the nebula’s bright central region are situated within a halo of colourful fragments of gas zooming away from the star.

This ring was ejected from the star at an earlier stage, before the main nebula at the centre formed. The whole nebula stands out against a backdrop teeming with distant galaxies, demonstrating how local astrophysical beauty and the farthest reaches of the cosmos can be seen together in modern astronomical surveys.

Within this broad view of the nebula and its surroundings, Hubble captures the very core of the billowing gas with high-resolution visible-light images, adding extra detail in the centre of this image. The data reveal a tapestry of concentric shells, jets of high-speed gas and dense knots sculpted by shock interactions, features that appear almost surreal in their intricacy. These structures are believed to record episodic mass loss from the dying star at the nebula’s centre, creating a kind of cosmic “fossil record” of its final evolutionary stages.

Combining the focused view of Hubble with Euclid’s deep field observations not only highlights the nebula’s exquisite structure but also places it within the broader context of the Universe that both space telescopes explore. Together, these missions provide a rich and complementary view of NGC 6543 – revealing the delicate interplay between stellar end-of-life processes and the vast surrounding space.

–o–

For more information, see here. There’s also this video which shows the Nebula in context in Euclid’s extraordinarily impressive wide field capability and Hubble’s superb resolution in the optical band:

P.S. I put the following on my office door in Maynooth University to demonstrate the true scale (!) of my own involvement in Euclid.

At least I’m on the first page!

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2026: The Year Ahead

Posted in Biographical, Euclid, Maynooth with tags , , , on January 1, 2026 by telescoper 
For last year’s words belong to last year’s language
And next year’s words await another voice.
And to make an end is to make a beginning.

From Four Quartets, ‘Little Gidding’ by T. S. Eliot.

So it’s New Year’s Day. Athbhliain faoi mhaise dhaoibh!

For me this brings the festive season to an end. I’ve been eating and drinking too much for the last week as one is supposed to. Last night I brought in the new year with a dish of roast duck and the last of the Christmas vegetables. I think I’ll be buying any sprouts and parsnips for a while. When the iron tongue of midnight told twelve, I had a glass of excellent Irish Whiskey in the form of Clonakilty Single Pot Still (46%). It has been a most enjoyable week, but heightened level of self-indulgence has been rather exhausting, and I’ll be taking things a bit easier for a few days before I go back to work on Monday. It’s hard work being a glutton.

Anyway, I thought I’d mention a few things looking forward to the New Year.

January will, as usual, be dominated by examinations, and especially the marking thereof. The first examination for which I am responsible is on January 12th. The examination, incidentally, will be held in the Glenroyal Hotel in Maynooth as the Sports Hall on campus – usually a major exam venue – is out of commission due to building work.

I have a couple of writing deadlines, in addition to having to correct the examinations, so it will be a busy January.

Then February sees the start of a new semester. I’ll be teaching Particle Physics again. I was a bit surprised to be asked to teach this again, as I was filling last year in for our resident particle physicist who was on sabbatical. I’m glad to be able to continue with it given the work I put in to do it last time. My other module is Computational Physics which I have taught at Maynooth every year since 2018, apart from 2024 when I was on sabbatical. This time, however, I will have to think hard about how to deal with the use of generative AI in the coursework.

Will I get to teach any astrophysics or cosmology at Maynooth before I retire? That’s looking very unlikely. I think it’s probable that the new academic year, starting in September, will find me teaching the same modules as last year.

The year ahead will also see the first data release (DR1) from the European Space Agency’s Euclid Mission. The date for that will be October 21st 2026. This is a hard deadline. There’s a huge amount of work going on within the Euclid Consortium to extract as much science as possible from the observations so far before the data becomes public, but you’ll have to wait until October to find out more!

This reminds me that I forgot to share this nice image from Euclid that was released just before Christmas.

Galaxy NGC 646 looking like a cosmic holiday garland in this image from the European Space Agency’s Euclid space telescope.

Once upon a time, WordPress used to send an email about the year’s blog statistics, etc, but it stopped doing that some time ago. I checked this morning, however, and learned that traffice on the blog in 2025 was up by 2.6% since 2024. I’m not sure how meaningful this is, because there is so much scraping going on these days. That figure doesn’t include the people who get posts via email or RSS or via other platforms such as the Fediverse.

While I’m on about social media I’ll mention a stat about my Bluesky account. I joined Bluesky in 2023 when I abandoned Xitter. As of today I have 8,078 BlueSky followers, which is more than I ever had on X, and with far higher levels of engagement and much friendlier interactions.

I’m also on Mastodon, although with a much smaller following (1.4k). This blog also has a separate existence on Mastodon here. I very much like the federated structure of Mastodon (which, incidentally, accords with my view of how academic publishing should be configured) and am a bit disappointed that it doesn’t seem to have caught on as much as it should.

That disappointment pales into insignificance, however, with the outrage I feel that my employer – along with most other universities – persists in using Xitter. Touting for trade in a far-right propaganda channel is no way for a institution of higher education to behave. You can read my views on this matter here.

And finally there’s the Open Journal of Astrophysics. The year ahead will see the 10th anniversary of our first ever publication – on an experimental prototype platform, long before we moved to Scholastica. It will be next Monday before we resume publishing, starting Volume 9. Which author(s) will be the first to get their final versions on arXiv in 2026? Stay tuned to find out!

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R.I.P. Yannick Mellier (1958-2025)

Posted in Euclid, R.I.P., The Universe and Stuff with tags , , , , on December 21, 2025 by telescoper

Last night I received a message via the Euclid Consortium conveying the very sad news of the death, at the age of 67, of the French astrophysicist and cosmologist Yannick Mellier (pictured left). Among many other things, Yannick was the Euclid Consortium Lead in which role he took on enormous responsibility for getting the project started and, with his team, keeping everything running. His loss is incalculable.

Yannick’s research work focussed on cosmology and the search for dark matter using gravitational lensing. Back in 1987 he was part of the observational team that discovered the first giant arc produced by strong gravitational lensing. He also did pioneering work in the field of weaking gravitational lensing with the Canada-France Hawaii Telescope in that regard starting back in 2000.

For well over a decade now Yannick had been involved with the European Space Agency’s Euclid mission. He was a major force right from the beginning, making the proposal, and after it was accepted leading the Consortium assembled to bring the project into being, preparing for launch, and dealing with the first data. The Euclid Consortium is a huge collaboration and it is impossible to overestimate the scale of the task facing the Lead. The first full data release (DR1) from Euclid will take place towards the end of next year (2026). It is sad beyong words that he did not live to see this.

During the period when I was Chair of the Euclid Consortium Diversity Committee I had a number of interactions with Yannick, sometimes dealing with difficult and confidential matters. I found him to be a man of great wisdom and sensitivity. Despite having many other things to deal with, including a long-term illness, he was unfailingly supportive and his advice was always sound.

The following is an excerpt from the message sent out yesterday:

Yannick’s death leaves a huge void within the consortium and our community. Those of us who have been here the longest know how hard he worked to make the Euclid project a success. He became its embodiment, working tirelessly to ensure its success; we owe him an immense debt of gratitude, and we will surely have the opportunity to reflect in detail on all that we owe him.

Indeed. I hope the Euclid Consortium – and the international cosmological community generally – will, at some stage, organize an appropriate tribute to Yannick.

Rest in Peace, Yannick Mellier (1958-2025)

Ar dheis Dé go raibh a anam

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Euclid’s “Tuning Fork”

Posted in Euclid, The Universe and Stuff with tags , , , on November 7, 2025 by telescoper

By way of a quick follow-up to yesterday’s post, here’s another Euclid Q1 product. This one is an updated version of the famous “Tuning Fork” representation of galaxy morphology:

Credits: Diagram: ESA/Euclid/Euclid Consortium/NASA, Diagram by J.-C. Cuillandre, L. Quilley, F. Marleau. Images alone: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre, E. Bertin, G. Anselmi

You can click on the image to make it (much) bigger.

A galaxy’s structure is a sign of its formation history and the environment in which it resides. Since early on, astronomers have ordered galaxies according to their visible structure – as a basis to understanding the underlying physics: This panorama of galaxies’ structure shows the ‘classical’ morphological sequence from ellipticals (E, left) to lenticulars (S0) through spirals (S) to irregulars and dwarfs (right). The fork divides barred and unbarred spiral families: originally only SA (unbarred) and SB (barred) galaxies were arranged in a ‘tuning fork’ layout, the addition of SAB (weakly barred) galaxies as a third branch is making this term increasingly challenging to use. Lowercase letters a to d indicate progressively later spiral stages (tighter to looser arms), the trailing m (e.g., SAm) denotes Magellanic, very-late-type systems (patchy, often one-armed). The Milky Way is classified as an SBc galaxy.

Below the main sequence there are three auxiliary panels showing objects not represented in the fork: (1) spiral galaxies seen edge-on, with varying bulge-to-disk ratios and warps; (2) interacting and merging galaxies illustrating gravitationally driven morphological change; and (3) the morphological diversity of dwarf galaxies.

You can read more about this image and the other Q1 results here. You can also find an interactive version of the plot here.

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Euclid and the Dark Cloud

Posted in Art, Euclid, The Universe and Stuff with tags , , , , on November 6, 2025 by telescoper

I haven’t posted anything recently about the European Space Agency’s Euclid mission, but I can remedy that by passing on a new image with text from the accompanying press release. This is actually just one of a batch of new science results emerging from the first `Quick Release’ (Q1) data; I blogged about the first set of Q1 results here.

Incidentally, I find the picture is very reminiscent of a famous painting by James McNeill Whistler.

Image description: The focus of the image is a portion of LDN 1641, an interstellar nebula in the constellation of Orion. In this view, a deep-black background is sprinkled with a multitude of dots (stars) of different sizes and shades of bright white. Across the sea of stars, a web of fuzzy tendrils and ribbons in varying shades of orange and brown rises from the bottom of the image towards the top-right like thin coils of smoke.

Technical details: The colour image was created from NISP observations in the Y-, J- and H-bands, rendered blue, green and red, respectively.  The size of the image is 11 232 x 12 576 pixels. The jagged boundary is due to the gaps in the array of NISP’s sixteen detectors, and the way the observations were taken with small spatial offsets and rotations to create the whole image. This is a common effect in astronomical wide-field images.

Accompanying Press Release

The above view of interstellar gas and dust was captured by the European Space Agency’s Euclid space telescope. The nebula is part of a so-called dark cloud, named LDN 1641. It sits at about 1300 light-years from Earth, within a sprawling complex of dusty gas clouds where stars are being formed, in the constellation of Orion.  

This is because dust grains block visible light from stars behind them very efficiently but are much less effective at dimming near-infrared light.  

The nebula is teeming with very young stars. Some of the objects embedded in the dusty surroundings spew out material – a sign of stars being formed. The outflows appear as magenta-coloured spots and coils when zooming into the image.  

In the upper left, obstruction by dust diminishes and the view opens toward the more distant Universe with many galaxies lurking beyond the stars of our own galaxy. 

Euclid observed this region of the sky in September 2023 to fine-tune its pointing ability. For the guiding tests, the operations team required a field of view where only a few stars would be detectable in visible light; this portion of LDN 1641 proved to be the most suitable area of the sky accessible to Euclid at the time. 

The tests were successful and helped ensure that Euclid could point reliably and very precisely in the desired direction. This ability is key to delivering extremely sharp astronomical images of large patches of sky, at a fast pace. The data for this image, which is about 0.64 square degrees in size – or more than three times the area of the full Moon on the sky – were collected in just under five hours of observations. 

Euclid is surveying the sky to create the most extensive 3D map of the extragalactic Universe ever made. Its main objective is to enable scientists to pin down the mysterious nature of dark matter and dark energy. 

Yet the mission will also deliver a trove of observations of interesting regions in our galaxy, like this one, as well as countless detailed images of other galaxies, offering new avenues of investigation in many different fields of astronomy. 

In visible light this region of the sky appears mostly dark, with few stars dotting what seems to be a primarily empty background. But, by imaging the cloud with the infrared eyes of its NISP instrument, Euclid reveals a multitude of stars shining through a tapestry of dust and gas. 

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Euclid Flagship 2 Update

Posted in Euclid, The Universe and Stuff with tags , , , on September 22, 2025 by telescoper

I was thinking earlier today that it’s been a while since I last posted anything about the European Space Agency’s Euclid Mission but I’ve got an excuse to remedy that today because there is a brand new a press release about the Euclid Consortium’s Flagship 2 simulations, a (low-resolution) visual representation of one of which is shown above.

The news is that the largest ever synthetic galaxy catalogue is now public; a team of 8 institutions within the Euclid Consortium, led by the Institute of Space Sciences (ICE-CSIC) and the Port d’Informació Científica (PIC) in Barcelona have developed this `mock’ catalogue, which includes 3.4 billion galaxies, each with 400 modelled properties available for the scientific community. It was constructed to help analyse data from the Euclid mission, but has many other potential uses so is being shared otuside the Consortium.

You can read more about this catalogue, and also find out how the access the simulated catalogues, here. You could also read the scientific paper describing the flagship simulations here.

P.S. The first main data release from Euclid (known to its friends as DR1) will take please on October 21, 2026. That’s just 13 months away…

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Wednesday at #EAS2025

Posted in Biographical, Euclid, The Universe and Stuff with tags , , , , on June 25, 2025 by telescoper

I spent most of today at the EAS 2025 sessions about Euclid. These were mainly about the Q1 data release I blogged about here, although there were some talks about what to expect about the first full data release (DR1), which is due towards the end of next year (2026), before I retire.

There were three Euclid sessions, one in the morning and two in the afternoon; I’m writing this during the last of these.

I was reminded this morning that the word “plenary” is derived from the Latin plenus, meaning “full”. This explains why there are no free seats for the plenary session, so I had to watch the stream in one of the overflow theatres.

I also attended a lunchtime session about the Square Kilometre Array Observatory (SKAO). This was interesting, though the first full data release from SKAO will not happen until after I’ve retired.

And, to end the day, I’m at a reception and meeting of SKA Ireland, a group campaigning for Ireland to join the SKAO.. There’s win.

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Last Remarks

Posted in Biographical, Education, Euclid, Maynooth, The Universe and Stuff, Uncategorized with tags , , on May 11, 2025 by telescoper

On Friday (9th May), the last day of undergraduate teaching at Maynooth, I gave the last lecture in my module on Particle Physics. I actually finished the syllabus on Tuesday (6th) so the final one was more a revision class than a lecture. I used it to go through some past examination questions and (try to) answer some general points raised by the class.

What surprised me about this lecture was that, as has usually been the case, there was more-or-less a full attendance. Examinations in Maynooth start on Friday (May 16th), but the Particle Physics examination is not until May 27th, near the end of the examination period. I therefore expected that many students would be concentrating on their revision for their other modules, which have exams earlier in the season or finishing their projects (which are due in before the exams start). There were one or two absences, but most came anyway. In fact there was even an extra student, one of our MSc students. When I saw him at the back of the lecture hall I asked, jokingly, why he had come. He replied “I haven’t got anything better to do”. I wasn’t sure how to interpret that!

That lecture was at 11am. Later that day, at 3pm, I gave a Departmental colloquium (which had quite a big audience). The title was Euclid: The Story So Far and the abstract was

The European Space Agency’s Euclid satellite was launched on 1st July 2023 and, after instrument calibration and performance verification, the main cosmological survey is now well under way. In this talk I will explain the main science goals of Euclid, give a brief summary of progress so far, showcase some of the science results already obtained, and set out the time line for future developments, including the main data releases and cosmological analysis.

The audience for these talks is very mixed: experimental and theoretical physics staff, postgraduates and even some undergraduate students (including some who were in my lecture earlier) so it was quite a general talk rather than one I might give to an specialist astrophysics audience. If you’re interested you can find the slides here.

Having a quick cup of tea after the end of the talk and before I headed off to catch the train, I talked briefly with a student who is taking his final examinations at Maynooth this year. He told me that I had actually given the first lecture he attended when he had just started his first year and the colloquium was the last talk he would attend at Maynooth. That would be the case for quite a few students in the audience, I suppose, but it won’t be true for any in future: I am no longer teaching any modules taken by first year students, and I’ll be retired when the current first year students graduate…

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