Oskar Klein Centre

Exciting news! The ESA - European Space Agency announced yesterday that the ARRAKIHS telescope is greenlit to be launched into space in 2030!

Stockholm University, a core partner in the mission will contribute to the cosmological simulations that turn ARRAKIHS's observations into insights about how galaxies form and what dark matter is made of.

The University's contribution is headed by Oskar Klein Centre Associate Professor Azadeh Fattahi.

"I've really enjoyed working with the team," says Fattahi. "They're enthusiastic, supportive and understanding, and they're a big part of why I enjoy this project so much. It's a really nice working environment."

https://www.okc.albanova.se/english/divisions/oskar-klein-centre/news/articles/2026-06-11-stockholm-researchers-help-launch-space-telescope-hunting-the-hidden-halos-of-galaxies

A supercomputer the size of a lunchbox, pointed at the dark Universe.

Soon, once the Vera C. Rubin Observatory and ESA - European Space Agency's Euclid mission start delivering data in earnest — around 20 terabytes a night from Rubin alone — handling it becomes a real challenge. At the Oskar Klein Centre (Stockholm University), Arthur Loureiro is prototyping a system of AI agents, named cosmoTRON, that takes on the repetitive parts of the analysis while keeping a human firmly in charge: every script it writes is saved so it can be checked and rerun.

It runs on a desktop NVIDIA DGX Spark you can hold in one hand. In its first test, it reproduced a standard cosmology calculation on its own. Built on a Swedish National Space Agency grant, out of the new EDUCATE Centre of Excellence at OKC.

Read more 👉 https://www.su.se/english/divisions/oskar-klein-centre/news/articles/2026-06-05-building-a-team-of-ai-agents-for-the-next-wave-of-cosmology-data

Some of the most sensitive telescopes ever built are listening for the faint afterglow of the Big Bang. To stop stray signals from drowning out that ancient light, their interiors are lined with fields of tiny pyramids — some no thicker than a business card — that soak up unwanted microwaves.

A new study led from the Oskar Klein Centre at Stockholm University set out to find what actually makes one of these absorbers good. Their research revealed that the shape and size of the pyramids matter more than the material they are made from. With the right geometry, four different designs each absorbed more than 99.7% of incoming microwaves.

The work — a collaboration with the University of Iceland Háskóli Íslands, Eindhoven University of Technology TU Eindhoven, and the Univerza v Ljubljani / University of Ljubljana, supported by the Swedish National Space Agency, Rymdstyrelsen — was selected as an Editors' Pick in Applied Optics, Optica.

https://www.su.se/english/divisions/oskar-klein-centre/news/articles/2026-06-03-shape-before-material-a-new-design-rule-for-microwave-absorbers-in-cosmic-telescopes

Our researchers Alex Pedrini and Angela Adamo are featured in INAF Media's coverage of their new Nature Astronomy paper: the most massive star clusters break out of their birth clouds faster, flooding their host galaxies with ultraviolet light. The team analysed nearly 9,000 clusters observed with JWST and Hubble.
(Article in Italian.)

Maggiore è la loro massa, prima vengono alla luce Gli ammassi stellari più massicci emergono più rapidamente dalle nubi in cui nascono, spazzando via il gas e inondando la galassia di luce ultravioletta. Il risultato arriva dall’analisi delle immagini di novemila ammassi ottenute con W

Ultra-faint dwarf galaxies, tiny satellite galaxies orbiting the Milky Way, have long been seen as cosmic fossils. Now, a new study by researchers at the Oskar Klein Centre and the LYRA collaboration uses an unprecedented set of simulations to show just how powerfully these faint systems can reflect the conditions of the early Universe and tell us why some galaxies grew and others did not.

Azadeh Fattahi is Associate Professor at the Oskar Klein Centre (OKC) and heading the research group which led this work, now published in Monthly Notices of the Royal Astronomical Society (MNRAS), together with collaborators from Durham University and University of Hawaii at Manoa UH Institute for Astronomy. She explains the scale of the project:

“In this work we presented a brand-new suite of cosmological simulations focused on the faintest galaxies in the Universe, with an unprecedented resolution. These are by far the largest sample of such galaxies ever simulated at these resolutions.”

https://www.su.se/english/news/articles/2026-04-24-local-dwarf-galaxies-may-preserve-a-record-of-the-infant-universe

Olivia Mostow (University of Virginia, US) is currently visiting the OKC on a Fulbright Research grant.

Learn more about how bursts of star formation within a galaxy can alter its central shape, and how the limitations of this process in especially faint galaxies may place pressure on our standard cosmological model.

🎥 New AAS Journals Video!

Olivia Mostow & Paul Torrey (Univ of Virginia) discuss their article on how bursty outflows and central potential fluctuations shape dark matter halos in classical and ultrafaint dwarf galaxies. youtu.be/a0mqKqEhmBI

The goal of this series is to connect authors with their article, their human story, and the larger community.

In a new report from the Oskar Klein Centre at Fysikum, Stockholm University, researchers Marcus Högås and Edvard Mörtsell show how classic Ising formulas can replace brute-force statistics when dealing with a very common problem: binary (“yes/no”) uncertainties in data. They package the result as two practical “recipes” that any scientist can plug into their existing analysis.

https://www.okc.albanova.se/english/divisions/oskar-klein-centre/news/articles/2025-12-19-bridging-physics-and-statistics-with-a-century-old-model

What powers the most extreme phenomena in the Universe—and what could they reveal about dark matter? Join us and explore high-energy astrophysics, particle acceleration, and beyond-standard-model signals in the non-thermal Universe.

Spring 2026 • 7.5 credits • Online via Zoom.

https://utbildning.su.se/english/education/course-catalogue/fk/fk8045

🤩 The Nordic Optical Telescope has contributed its observations to a milestone: the first ever spatially resolved, gravitationally lensed superluminous supernova, SN 2025wny. Early ALFOSC spectroscopy of this extraordinary transient confirmed that it was a supernova at an incredible distance, whose light has travelled almost 10 billion years to reach us, meaning that when that light was emitted, the Universe was “only” about 4 billion years old.

🔭 This discovery, led by Joel Johansson of the Oskar Klein Centre (OKC) at Stockholm University and carried out by an international research team, includes among its first authors Ariel Goobar (OKC) and Dan Perley and Jacob Wise of Liverpool John Moores University (LJMU). This also highlights the power of coordinated follow-up: while the NOT spectra identified the event as a supernova, our neighbours across the hill at the observatory, the Liverpool Telescope (LT), provided crucial images that resolved four separate images of SN 2025wny, a stunning demonstration of the gravitational lensing effect in action.

🧐 See the press release here: https://www.su.se/english/news/articles/2025-12-12-astronomers-discover-the-first-gravitationally-lensed-superluminous-supernova

Oskar Klein Centre researchers Prof. Göran Östlin and Jens Melinder at the Stockholm University Astronomy Department , has identified nine galaxies that may be the most distant ever discovered!

A study led by Pablo Pérez-González at the Centro de Astrobiología (Spain), with collaborators from the Department of Astronomy at Stockholm University, has identified nine galaxies 🌌 that may be the most distant ever discovered!

These galaxies were found through deep infrared imaging as part of the MIDIS survey led by Prof. Göran Östlin in our department 🤩. By combining nearly 90 hours of JWST observations, the team could detect these faint galaxies whose light was emitted just 100–200 million years after the Big Bang 💥

“I expected to find a few very distant galaxies… but discovering nine that far away was a huge surprise!” said Pablo Pérez-González

This discovery pushes the boundaries of what we know about when and how galaxies first formed and once again proves that JWST is changing our understanding and current knowledge about the universe. 🥳🥳

📸 Pablo Pérez-González