It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
America’s fascist dress rehearsal including torture, dehumanization, and the collapse of democratic norms are no longer theoretical—they’re preparing for the opening act.
We inhabit a historical moment that resurrects, with chilling familiarity, the state terrorism once made visible under Hitler, Franco, Mussolini, Pinochet, and other dictators who transformed cruelty into a governing philosophy. Central to such regimes lies a single, devastating truth: the law collapses the moment violence becomes its substitute. In this descent, due process evaporates, political opponents are rebranded as “terrorists,” and violence becomes the organizing principle of power. Independent media are smeared or silenced, universities are targeted for their critical capacities, and the spectacle of brown-shirted, goose-stepping thugs hunting down racialized others slips back into public view as a normalized, even celebrated, form of civic life.
Policies soaked in blood are repackaged as entertainment, folded into a culture industry that echoes the aestheticized fascism of Leni Riefenstahl, spectacles designed to numb, seduce, and train the public in the pleasures of violence. The brutality unleashed by the Trump administration against critics, immigrants, cities, political enemies, and so-called terrorists is more than an echo of fascism’s mobilizing passions; it is a signal of what is to come. Its endpoint can be found in the concentration camps and gulags of the 20th century. And the road to the camps always begins the same way: with the brutalization of the innocent in modern-day torture chambers.
This is the central lesson of the illegal abduction and exile of Venezuelans to one of the most notorious prisons in El Salvador—a maximum-security torture chamber run by Nayib Bukele. It is a canary in the coal mine, a rehearsal for the next stage of violence that will be unleashed on Americans. More than 200 Venezuelan migrants were seized and sent to a notorious maximum-security torture dungeon in El Salvador run by Nayib Bukele, a ruthless dictator, punished not for crimes, but for the ink on their skin. Their tattoos were read as threats, their bodies as evidence. Later, they were deported to Venezuela as part of a large-scale prisoner exchange among the United States, Venezuela, and El Salvador, an arrangement that saw ten Americans held in Venezuela freed in return for the Venezuelan deportees.
As reported in The New York Times, many of the men testified that while imprisoned “they were shackled, beaten, shot with rubber bullets and tear gassed until they passed out. They said they were punished in a dark room called the island, where they were trampled, kicked and forced to kneel for hours. One man said officers thrust his head into a tank of water to simulate drowning. Another said he was forced to perform oral sex on guards wearing hoods.” What emerges here is not simply a catalogue of human-rights abuses, nor merely the grotesque suspension of due process; it is the language of barbarism made policy, brutality elevated to the level of governance. These acts, carried out under the pretext of fighting terrorism, reveal themselves for what they are: the state-sanctioned machinery of a racialized war, a campaign of terror unleashed by the Trump regime against immigrants. Such violence does more than break bodies, it shreds the very fabric of a democratic society–teaching a lesson no nation should ever teach: that some lives can be debased with impunity.
The dreams of annihilation extend from the genocidal slaughter of indigenous populations to its updated colonial and racialized version in American slavery, Hitler’s dreams of racial purity, and Trump and Miller’s embrace of the delusions of white nationalism and white supremacy are back. The Mein Kampf dream-world of masters and servants no longer parade as a fixed repository of history; they have become the present modeled after history.
We live in a world in which stupidity and cowardice no longer hide in the shadows, it now thrives in a culture of massive inequality, precarity, racism, misogyny, and moral collapse. The vans of death are designed not just for immigrants, trans people, and Black and brown people, they are eager to come for anyone who does not surrender to fascist cult led by Trump and his barbaric ilk. The horror inflicted on more than 200 Venezuelans in Bukele’s torture chamber was not an endpoint but a prelude, an experiment in something far more expansive and deadly.
History offers echoes and warnings, and writers who lived through earlier dictatorships remind us of their enduring lessons. Ariel Dorfman, writing about the barbarous Pinochet regime, reminds us that the lessons of history matter as both a form of moral witnessing and a source of collective resistance. He makes clear with a sense of urgency that “that ordinary men and women can find at the most dire and dangerous moments in their lives, the courage and wisdom to resist injustice, so that the crimes of their day—and, alas, of ours—need not be endlessly repeated tomorrow.” We can only hope that in such dark times his words represent more than a warning but also a call to action.Email
Henry Giroux (born 1943) is an internationally renowned writer and cultural critic, Professor Henry Giroux has authored, or co-authored over 65 books, written several hundred scholarly articles, delivered more than 250 public lectures, been a regular contributor to print, television, and radio news media outlets, and is one of the most cited Canadian academics working in any area of Humanities research. In 2002, he was named as one of the top fifty educational thinkers of the modern period in Fifty Modern Thinkers on Education: From Piaget to the Present as part of Routledge’s Key Guides Publication Series.
Wednesday, December 03, 2025
SPACE/COSMOS
Astronomers spot one of the largest spinning structures ever found in the Universe
A figure illustrating the rotation of neutral hydrogen (right) in galaxies residing in an extended filament (middle), where the galaxies exhibit a coherent bulk rotational motion tracing the large-scale cosmic web (left). Credit: Lyla Jung
An international team led by the University of Oxford has identified one of the largest rotating structures ever reported: a “razor-thin” string of galaxies embedded in a giant spinning cosmic filament, 140 million light-years away. The findings, published today (4 December) in Monthly Notices of the Royal Astronomical Society, could offer valuable new insights into how galaxies formed in the early Universe.
Cosmic filaments are the largest known structures in the Universe: vast, thread-like formations of galaxies and dark matter that form a cosmic scaffolding. They also act as ‘highways’ along which matter and momentum flow into galaxies. Nearby filaments containing many galaxies spinning in the same direction- and where the whole structure appears to be rotating – are ideal systems to explore how galaxies gained the spin and gas they have today. They can also provide a way to test theories about how cosmic rotation builds up over tens of millions of light-years.
In the new study, the researchers found 14 nearby galaxies rich in hydrogen gas, arranged in a thin, stretched-out line about 5.5 million light-years long and 117,000 light-years wide. This structure sits inside a much larger cosmic filament containing over 280 other galaxies, and roughly 50 million light-years long. Remarkably, many of these galaxies appear to be spinning in the same direction as the filament itself- far more than if the pattern of galaxy spins was random. This challenges current models and suggests that cosmic structures may influence galaxy rotation more strongly or for longer than previously thought.
The researchers found that the galaxies on either side of the filament's spine are moving in opposite directions, suggesting that the entire structure is rotating. Using models of filament dynamics, they inferred the rotation velocity of 110 km/s and estimated the radius of the filament’s dense central region at approximately 50 kiloparsecs (about 163,000 light-years).
Co-lead author Dr Lyla Jung (Department of Physics, University of Oxford) said: "What makes this structure exceptional is not just its size, but the combination of spin alignment and rotational motion. You can liken it to the teacups ride at a theme park. Each galaxy is like a spinning teacup, but the whole platform- the cosmic filament -is rotating too. This dual motion gives us rare insight into how galaxies gain their spin from the larger structures they live in.”
The filament appears to be a young, relatively undisturbed structure. Its large number of gas-rich galaxies and low internal motion - a so-called “dynamically cold” state - suggest it’s still in an early stage of development. Since hydrogen is the raw material for star formation, galaxies that contain much hydrogen gas are actively gathering or retaining fuel to form stars. Studying these galaxies can therefore give a window into early or ongoing stages of galaxy evolution.
Hydrogen-rich galaxies are also excellent tracers of gas flow along cosmic filaments. Because atomic hydrogen is more easily disturbed by motion, its presence helps reveal how gas is funnelled through filaments into galaxies -offering clues about how angular momentum flows through the cosmic web to influence galaxy morphology, spin, and star formation.
The discovery could also inform future efforts to model intrinsic alignments of galaxies, a potential contaminant in upcoming weak lensing cosmology surveys with European Space Agency's Euclid mission and the Vera C. Rubin Observatory in Chile.
Co-lead author Dr Madalina Tudorache (Institute of Astronomy, University of Cambridge / Department of Physics, University of Oxford) added: "This filament is a fossil record of cosmic flows. It helps us piece together how galaxies acquire their spin and grow over time."
The international team used data from South Africa’s MeerKAT radio telescope, one of the world’s most powerful telescopes, comprising an array of 64 interlinked satellite dishes. This spinning filament was discovered using a deep survey of the sky called MIGHTEE, which is led by Professor of Astrophysics Matt Jarvis (Department of Physics, University of Oxford). This was combined with optical observations from the Dark Energy Spectroscopic Instrument (DESI) and Sloan Digital Sky Survey (SDSS) to reveal a cosmic filament exhibiting both coherent galaxy spin alignment and bulk rotation.
Professor Jarvis said: “This really demonstrates the power of combining data from different observatories to obtain greater insights into how large structures and galaxies form in the Universe. Such studies can only be achieved by large groups with diverse skillsets, and in this case, it was really made possible by winning an ERC Advanced Grant/UKIR Frontiers Research Grant, which funded the co-lead authors.”
The study also involved researchers from University of Cambridge University of the Western Cape Rhodes University, South African Radio Astronomy Observatory, University of Hertfordshire, University of Bristol, University of Edinburgh, and University of Cape Town.
Notes to editors:
For media enquiries and interview request, contact:
The paper ‘A 15 Mpc rotating galaxy filament at redshift 𝑧 = 0.032’ will be published in Monthly Notices of the Royal Astronomical Society at 00:01 GMT Thursday 4 December / 19:01 ET Wednesday 3 December 2025 at https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/staf2005 . To view a copy of the paper before this under embargo, please contact the researchers listed above.
Oxford University has been placed number 1 in the Times Higher Education World University Rankings for the tenth year running, and number 3 in the QS World Rankings 2024. At the heart of this success are the twin-pillars of our ground-breaking research and innovation and our distinctive educational offer.
Oxford is world-famous for research and teaching excellence and home to some of the most talented people from across the globe. Our work helps the lives of millions, solving real-world problems through a huge network of partnerships and collaborations. The breadth and interdisciplinary nature of our research alongside our personalised approach to teaching sparks imaginative and inventive insights and solutions.
Through its research commercialisation arm, Oxford University Innovation, Oxford is the highest university patent filer in the UK and is ranked first in the UK for university spinouts, having created more than 300 new companies since 1988. Over a third of these companies have been created in the past five years. The university is a catalyst for prosperity in Oxfordshire and the United Kingdom, contributing around £16.9 billion to the UK economy in 2021/22, and supports more than 90,400 full time jobs.
Journal
Monthly Notices of the Royal Astronomical Society
Article Title
A 15 Mpc rotating galaxy filament at redshift 𝑧 = 0.032
SwRI may have solved a mystery surrounding Uranus’ radiation belts
Solar-storm-driven waves may explain extreme radiation
SwRI scientists compared space weather impacts of a fast solar wind structure (first panel) driving an intense solar storm at Earth in 2019 (second panel) with conditions observed at Uranus by Voyager 2 in 1986 (third panel) to potentially solve a 39-year-old mystery about the extreme radiation belts found. The ‘chorus’ wave is a type of electromagnetic emission that may accelerate electrons and could have resulted from the solar storm.
SAN ANTONIO — December 3, 2025 — Southwest Research Institute (SwRI) scientists believe they may have resolved a 39-year-old mystery about the radiation belts around Uranus.
In 1986, when Voyager 2 made the first and only flyby of Uranus, it measured a surprisingly strong electron radiation belt at significantly higher levels than anticipated. Based on extrapolations from other planetary systems, Uranus’ electron radiation belt was off the charts. Since then, scientists have wondered how the Uranian system could support such an intense trapped electron radiation belt, at a planet unlike anything else in the solar system.
Based on new analyses, SwRI scientists theorize that Voyager 2 observations may have more in common with processes at Earth driven by large solar wind storms. Scientists now think a solar wind structure — known as a co-rotating interaction region — was likely passing through the Uranian system. This could explain the extreme energy levels Voyager 2 observed.
“Science has come a long way since the Voyager 2 flyby,” said SwRI’s Dr. Robert Allen, lead author of a paper outlining this research. “We decided to take a comparative approach looking at the Voyager 2 data and compare it to Earth observations we’ve made in the decades since.”
This new study indicates that the Uranian system may have experienced a space weather event during the Voyager 2 visit that led to powerful high-frequency waves, the most intense observed over the entirety of the Voyager 2 mission. In 1986, scientists thought that these waves would scatter electrons to be lost to Uranus’s atmosphere. But since then, Allen said, scientists have learned that those same waves under certain conditions can also accelerate electrons and feed additional energy into planetary systems.
“In 2019, Earth experienced one of these events, which caused an immense amount of radiation belt electron acceleration,” said SwRI’s Dr. Sarah Vines, a co-author of the paper. “If a similar mechanism interacted with the Uranian system, it would explain why Voyager 2 saw all this unexpected additional energy.”
But these findings also raise a lot of additional questions about the fundamental physics and sequence of events that would enable these intense wave emissions.
“This is just one more reason to send a mission targeting Uranus,” Allen said. “The findings have some important implications for similar systems, such as Neptune’s.”
The paper “Solving the mystery of the electron radiation belt at Uranus: Leveraging knowledge of Earth’s radiation belts in a re-examination of Voyager 2 observations” is published in Geophysical Research Letters and is accessible at DOI: 10.1029/2025GL119311.
“Solving the mystery of the electron radiation belt at Uranus: Leveraging knowledge of Earth’s radiation belts in a re-examination of Voyager 2 observations”
Groundbreaking simulations show how black holes glow bright
New simulations created by astrophysicists at the Flatiron Institute and the Institute for Advanced Study reveal how material flowing around and into black holes creates intense light shows
Near the black hole (shown in the center), an accretion flow forms a dense, thin thermal disk embedded within a magnetically dominated envelope that helps stabilize the system. The flow is radiation-dominated and highly turbulent, yet the central thermal disk structure (yellow) remains remarkably stable.
Surprisingly, some of the universe’s brightest objects are black holes. As scorching gas and dust flow around and into a black hole, they glow with fierce intensity across the light spectrum. Now, a team of computational astrophysicists has developed the most comprehensive simulations ever made of how black holes create these dazzling light shows.
Using supercomputers, the researchers calculated the behavior of material zipping around black holes. Unlike all previous studies that relied on simplifying approximations, the researchers utilized a full treatment of how light moves and interacts with matter within Albert Einstein’s general relativity.
Their results could help explain the hundreds of strange, faintly luminous objects known as little red dots (LRDs) spotted in the early universe by the James Webb Space Telescope. A leading theory, supported by the new results, proposes that these dots are black holes that are consuming material through a process called ‘super-Eddington accretion’ in the hearts of primordial galaxies.
“This is the first time we’ve been able to see what happens when the most important physical processes in black hole accretion are included accurately,” says Lizhong Zhang, lead author of the study and a research fellow at the Simons Foundation’s Flatiron Institute in New York City. “Any oversimplifying assumption can completely change the outcome. What’s most exciting is that our simulations now reproduce remarkably consistent behaviors across black hole systems seen in the sky, from ultraluminous X-ray sources to X-ray binaries. In a sense, we’ve managed to ‘observe’ these systems not through a telescope, but through a computer.”
Zhang is a joint postdoctoral research fellow in the Institute for Advanced Study (IAS) in Princeton, New Jersey, and the Flatiron Institute’s Center for Computational Astrophysics (CCA). Zhang co-authored the new study with collaborators at IAS, the CCA, Los Alamos National Laboratory and the University of Virginia. The study is the first in a series of papers that will present the team’s novel computational approach and its applications to several classes of black hole systems.
Due to their extreme gravity, no model of black holes would be considered complete without the incorporation of Einstein’s theory of general relativity, which describes how the most massive bodies distort the fabric of space-time. That space-time distortion shapes how the light created by the infalling material moves and interacts with the surrounding material.
Those full general relativistic equations are tough to solve, even for powerful computers. Previous simulations took shortcuts by simplifying the calculations of radiation. “Previous methods used approximations that treat radiation as a sort of fluid, which does not reflect its actual behavior,” Zhang explains.
By combining insights gained over decades of work, the team developed new algorithms that can directly solve the equations without sacrificing accuracy or requiring unreasonable amounts of computational power. “Ours is the only algorithm that exists at the moment that provides a solution by treating radiation as it really is in general relativity,” says Zhang.
Their paper addresses accretion onto stellar mass black holes, which are approximately 10 times the mass of the sun, though relative lightweights compared to Sagittarius A*, the supermassive black hole at the center of our galaxy, which has a mass more than 4 million times that of our sun.
Simulations are essential for understanding stellar mass black holes. While high-resolution images have been produced of supermassive black holes, those with stellar mass cannot be observed in the same way, appearing only as pinpoints of light. Instead, researchers must convert the light into a spectrum, which provides the data to map the distribution of energy around a black hole. Compared with supermassive black holes, which evolve over years or even centuries, stellar mass black holes change on human timescales of minutes to hours, making them ideal for studying the evolution of these systems in real-time.
Through their simulations, the scholars captured how matter behaves as it spirals toward stellar mass black holes, forming turbulent radiation-dominated disks, launching powerful winds and sometimes even producing powerful jets. The team found that their model fit remarkably well with the light spectrum obtained from observational data. This agreement between the simulation and observation is crucial, allowing for improved interpretations of the limited data available for these distant objects.
Zhang and his research team were granted access to two of the world’s most powerful supercomputers, Frontier and Aurora, housed at Oak Ridge National Laboratory and Argonne National Laboratory, respectively, to model black hole accretion. These ‘exascale’ computers are capable of performing a quintillion operations per second.
Even with all that computational power, the researchers still needed clever code and complex mathematics to get accurate results. Christopher White of the CCA and Princeton University led the design of the radiation transport algorithm. Patrick Mullen of Los Alamos National Laboratory helmed the implementation of the algorithm in code optimized for exascale computing. The simulations were built on top of an algorithm developed by the CCA’s Yan-Fei Jiang that combines an angle-dependent algorithm that tracks the way radiation interacts and moves with a model of how fluid flows around a rotating sphere in the presence of a strong magnetic field. (Jiang’s work is now widely used across the astrophysics community for objects such as black holes and massive stars.)
In the future, the team behind the new simulations will work to determine if the model applies to all types of black holes. In addition to stellar mass black holes, their simulations may enhance understanding of supermassive black holes, which drive the evolution of galaxies, as well as further investigate the identity of the James Webb Space Telescope’s little red dots. The simulations indicate that these objects may be producing more light than the Eddington limit — a balance between the gravitational force pulling material inward and the outward pressure of radiation released by the infalling matter, assuming a perfect spherical flow. In this case, the black holes are radiating more energy than can be balanced by the inward pull of gravity.
The team will continue to evolve its approach to account for the different ways radiation interacts with matter across a wide range of temperatures and densities.
“Now the task is to understand all the science that is coming out of it,” says James Stone, an IAS professor and co-author of the new paper.
About the Flatiron Institute
The Flatiron Institute is the research division of the Simons Foundation. The institute's mission is to advance scientific research through computational methods, including data analysis, theory, modeling and simulation. The institute's Center for Computational Astrophysics creates new computational frameworks that allow scientists to analyze big astronomical datasets and to understand complex, multi-scale physics in a cosmological context.
This image shows the gas density in a two-dimensional cross-section of an accreting black hole. Brighter areas represent regions of higher density. Near the black hole, the accretion flow forms a dense, thin thermal disk embedded within a magnetically dominated envelope that helps stabilize the system. Although the flow is radiation-dominated and highly turbulent, the thermal disk structure remains remarkably stable.
Building on decades of effort, a team of computational astrophysicists has achieved a major milestone: developing the most comprehensive model to date of luminous black hole accretion. Leveraging the world’s most powerful supercomputers, the researchers have, for the first time, calculated the flow of matter into black holes in full general relativity and in the radiation-dominated regime without using simplifying approximations.
The work, published today in The Astrophysical Journal, was led by researchers from the Institute for Advanced Study and the Flatiron Institute, Center for Computational Astrophysics. It is the first in a series of papers that will present the team’s novel computational approach and its applications to several classes of black hole systems.
“This is the first time we’ve been able to see what happens when the most important physical processes in black hole accretion are included accurately. These systems are extremely nonlinear—any over-simplifying assumption can completely change the outcome. What’s most exciting is that our simulations now reproduce remarkably consistent behaviors across black hole systems seen in the sky, from ultraluminous X-ray sources to X-ray binaries. In a sense, we’ve managed to ‘observe’ these systems not through a telescope, but through a computer,” stated the study’s lead author, Lizhong Zhang. Zhang is a joint postdoctoral research fellow in the Institute for Advanced Study’s School of Natural Sciences and the Flatiron Institute’s Center for Computational Astrophysics, having initiated the project during his first year at IAS (2023–24) before continuing it at Flatiron.
Due to their extreme gravity, no model of black holes would be considered complete without the incorporation of Einstein’s theory of general relativity, which describes how the most massive bodies distort the fabric of spacetime. Moreover, when large amounts of matter accrete onto a black hole, a full treatment of how the radiation (light) released moves through that curved spacetime and interacts with surrounding gas is also crucial. However, previous simulations have not been able to take into account these full mathematical complexities. Just as a physics student learns by working with simplified or “toy” models that capture only a subset of the real world’s variables, earlier efforts to simulate radiation flows around black holes took necessary shortcuts to simplify the problem.
“Previous methods used approximations that treat radiation as a sort of fluid, which does not reflect its actual behavior,” explained Zhang.
Those previous approximations were necessary because the full equations are extremely complex and computationally demanding. But, through joining together insights gained over decades of work, the team developed new algorithms that directly solve them, without approximations. “Ours is the only algorithm that exists at the moment that provides a solution by treating radiation as it really is in general relativity,” he added.
Their paper specifically addresses accretion onto stellar mass black holes, which are approximately 10 times the mass of the Sun—relative lightweights compared to Sgr A*, the supermassive black hole at the center of our galaxy. Simulations are essential for understanding such black holes. While high-resolution images have been produced of supermassive black holes, those with stellar mass cannot be observed in the same way, appearing only as pinpoints of light. Instead, researchers must convert the light into a spectrum, which provides the data to map the distribution of energy around a black hole. Compared with supermassive black holes, which evolve over years or even centuries, stellar mass black holes change on human timescales of minutes to hours, making them ideal for studying the evolution of these systems in real time.
Through their simulations, the scholars captured how matter behaves as it spirals toward stellar mass black holes, forming turbulent, radiation-dominated disks, launching powerful winds, and sometimes even producing powerful jets. The team found that their model fit remarkably well with the spectrum obtained from observational data. This agreement between the simulation and observation is crucial, allowing for stronger interpretations of the limited data available for these distant objects.
The Institute for Advanced Study has a long-standing tradition of pioneering computer modeling of complex systems, which has proven vital to the advancement of human knowledge. One early example is the Institute’s Electronic Computer Project, led by founding Professor (1933–55) John von Neumann, which provided insight into a variety of fields including fluid dynamics, climate science, and nuclear physics. Building on this legacy, Zhang and his research team were granted access to two of the world’s most powerful supercomputers, Frontier and Aurora, housed at Oak Ridge National Laboratory and Argonne National Laboratory, respectively, to model black hole accretion. These “exascale” computers, capable of performing a quintillion operations per second, can occupy thousands of square feet—evoking the room-filling scale of the earliest computers.
To realize the potential of these massive computing resources, the team required complex mathematics and code equal to the task. The team’s success in this regard was enabled by Christopher White of the Flatiron Institute and Princeton University, who led the design of the radiation transport algorithm, and Patrick Mullen, Member (2021–22) in the School of Natural Sciences, now based at Los Alamos National Laboratory, who led the implementation of the algorithm in the AthenaK code which is optimized for exascale computing.
In the future, the team will work to determine if their model is applicable to all types of black holes. In addition to stellar mass black holes, their simulations may enhance understanding of supermassive black holes, which drive the evolution of galaxies. The team will continue to evolve its approach to account for the different ways radiation interacts with matter across a wide range of temperatures and densities.
“What makes this project unique is, on the one hand, the time and effort it has taken to develop the applied mathematics and software capable of modeling these complex systems, and, on the other hand, having a very large allocation on the world’s largest supercomputers to perform these calculations,” explained James Stone, Professor in the Institute for Advanced Study’s School of Natural Sciences and paper co-author. “Now the task is to understand all the science that is coming out of it.”
About the Institute
The Institute for Advanced Study has served as one of the leading independent centers for theoretical research and intellectual inquiry since its establishment in 1930, advancing the frontiers of knowledge across the sciences and humanities. From founding IAS Faculty Albert Einstein, Erwin Panofsky, and John von Neumann to influential figures Emmy Noether, George Kennan, and J. Robert Oppenheimer to the foremost thinkers of the present, IAS is dedicated to enabling independent inquiry and fundamental discovery.
Each year, the Institute welcomes more than 250 of the world’s most promising post-doctoral researchers and scholars who are selected and mentored by a permanent Faculty, all of whom are preeminent leaders in their fields. Among present and past Faculty and Members, there have been 37 Nobel Laureates, 46 of the 64 Fields Medalists, and 24 of the 28 Abel Prize Laureates, as well as winners of the Turing Award; the Pulitzer Prize in History; the Wolf, Holberg, and Kluge prizes; and many MacArthur and Guggenheim fellows, among other honors.
Radiation GRMHD Models of Accretion onto Stellar-mass Black Holes. I. Survey of Eddington Ratios
Article Publication Date
3-Dec-2025
This image shows how gas and magnetic fields behave around a fast-spinning black hole that is capturing matter at an extremely high rate. The thick, donut-shaped disk of gas around the black hole gets denser toward its middle. In this image, brighter purple areas indicate that the gas is denser, while darker purple areas have less gas. Near the black hole, a powerful jet shoots outward, guided by spiral-shaped magnetic fields. The colorful lines in the image trace the jet's magnetic fields, and their colors reveal the field strength: red and orange show stronger magnetic fields, while yellow and green show weaker ones.
Credit
Zhang et al. (2025)
SPHERE’s debris disk gallery: tell-tale signs of dust and small bodies in distant solar systems
Images of dust around distant exoplanets provide a glimpse of asteroids and comets in other solar systems
This image presents a grid of colour-enhanced astronomical observations, each depicting a circumstellar disc—structures of dust and gas surrounding stars. Every square in the grid represents a different star system, identified by catalogue names such as “HD 105”, “HD 377”, or “TWA 25”. The discs vary widely in shape, size, and orientation: some appear as well-defined rings, while others show elongated or irregular forms. The colour palette, dominated by purples and oranges, highlights brightness and contrast to reveal structural details. This visual diversity reflects different physical properties and evolutionary stages of the star systems, offering valuable insights into planetary formation and stellar development.
Observations with the instrument SPHERE at ESO’s Very Large Telescope have produced an unprecedented gallery of “debris disks” in exoplanetary systems. Gaël Chauvin (Max Planck Institute for Astronomy), project scientist of SPHERE and co-author on the paper publishing the results, says: “This data set is an astronomical treasure. It provides exceptional insights into the properties of debris disks, and allows for deductions of smaller bodies like asteroids and comets in these systems, which are impossible to observe directly.”
In our own solar system, once you look beyond the Sun, the planets, and dwarf planets like Pluto, there is a bewildering array of smaller (“minor”) bodies. Of particular interest are the larger small bodies, with diameters between about a kilometer and several hundred kilometers. We call those objects comets if they put on (at least occasionally) a display of losing gas and dust to form distinctive visible structures like a tail, and asteroids when they don’t. Small bodies provide a glimpse of the earliest history of the solar system: In the evolution from dust grains to full-size planets, small bodies called planetesimals are a transitional stage, and the asteroids and comets are remnants from that stage – planetesimals that did not manage to evolve into larger planets. Small bodies are (somewhat) modified remnants of the building material for planets like our Earth!
Small bodies around stars other than the Sun?
So far, astronomers have detected more than 6000 exoplanets (that is, planets orbiting stars other than the Sun), giving us a much better idea of the diversity of planets out there, and of the place of our solar system within this teeming population. Taking actual images of such planets is a considerable challenge, though. At this time, there are less than 100 exoplanets that astronomers have been able to image, and even giant planets are no more than a structureless little blob on such images. “Finding any direct clues about the small bodies in a distant planetary system from images seems downright impossible. The other indirect methods used to detect exoplanets are no help, either” says Dr Julien Milli, astronomer at the University Grenoble Alpes and co-author of the study.
The solution, ironically, comes from stuff that is even smaller, by orders of magnitude. In particular in younger planetary systems, planetesimals will regularly collide – sometimes to stick together to form a larger body, sometimes to go their separate ways. These collisions create copious amounts of new dust, and the dust, it turns out, can be observed over large distances, given suitable instruments: Whenever you divide an object into smaller components, the total volume remains the same, but the total surface area increases. Divide an asteroid with a diameter of one kilometer into dust grains with diameters of one micrometer (= millionth of a meter), and you increase the overall surface by a factor of a billion! That is, in large part, why it is possible to observe debris disks around young stars by the starlight they reflect. Observe the dust, and you can glean information about the planetary system’s small bodies.
Observing debris disks
Over time, such a debris disk will fade. Collisions will become less frequent. Dust will be blown out of the system by radiation pressure, caught by planetesimals or planets, or ends up in the central star. Our own solar system provides an example of what is left after billions of years: In this case, there are two remaining planetesimal belts, namely the asteroid belt between Mars and Jupiter, and a reservoir of comets outside the orbits of the giant planets in what is known as the Kuiper belt. There is also dust in our solar system’s main orbital light, known as zodiacal dust. Under a very dark sky, you will be able to see light reflected by that dust with the naked eye shortly after sunset or shortly before sunset, the so-called zodiacal light.
This configuration would be difficult to detect for alien astronomers studying our solar system from afar. But as the present study has shown, with the best current telescopes and instruments, for not-too-far-away systems, the dust should be observable for about the first 50 million years of the debris disk’s life. Which is not to say that such observations are not a considerable technical challenge! Imaging a debris disk is like taking a picture of a puff of cigarette smoke, but the smoke is hovering next to a bright stadium floodlight, and you are trying to take the picture from a distance of several kilometers. This is where suitable instrumentation makes all the difference, and it is where the SPHERE instrument, which began operating at one of ESO’s Very Large Telescopes (VLT) in the spring of 2014, excels.
Blocking out starlight
At the heart of SPHERE is a very simple concept. If in everyday life, we want to look at something and the Sun in the background is making this difficult, we put up a hand to block out the sunlight. When SPHERE observes an exoplanet or debris disk, it uses a coronagraph to block out the star’s light – in effect, a little disk inserted in the optical pathway that removes most of the starlight before the image is taken. The catch is that unless imaging is very precise and stable, this simple recipe cannot work in practice!
To meet the stringent requirements, SPHERE utilizes an extreme version of adaptive optics, where the unavoidable perturbations caused by the light passing through Earth’s atmosphere are analyzed and largely compensated for in real time through the use of a deformable mirror. Another, optional part of SPHERE filters out light with specific properties (“polarised light”) that are characteristic for light reflected by something like dust particles, as opposed to starlight, setting the stage for particularly sensitive debris disk images.
An unprecedented gallery of debris disk images
The new publication presents an unprecedented collection of debris disk images, produced with SPHERE from starlight reflected by small dust particles in these systems. "To obtain this collection, we processed data from observations of 161 nearby young stars whose infrared emission strongly indicates the presence of a debris disk," says Natalia Engler (ETH Zurich), the lead author of the study. "The resulting images show 51 debris disks with a variety of properties — some smaller, some larger, some seen from the side and some nearly face-on – and a considerable diversity of disk structures. Four of the disks had never been imaged before."
Comparisons within a larger sample are crucial for discovering the systematics behind object properties. In this case, an analysis of the 51 debris disks and their stars confirmed several systematic trends: When a young star is more massive, its debris disk tends to have more mass as well. The same is true for debris disks where the majority of the material is located at a greater distance from the central star.
Finding asteroid belts and Kuiper belts in other systems
Arguably the most interesting feature of the SPHERE debris disks are the structures within the disks themselves. In many of the images, disks have a concentric ring- or band-like structure, with disk material predominantly found at specific distances from the central star. The distribution of small bodies in our own solar system has a similar structure, with small bodies concentrated in the asteroid belt (asteroids) and the Kuiper belt (comets).
All of these belt structures appear to be associated with the presence of planets, specifically of giant planets, clearing their neighbourhoods of smaller bodies. Some of the giant planets had been observed already. In some of the SPHERE images, features like sharp inner edges or disk asymmetries give tantalizing hints of as-yet unobserved planets. In this way, the SPHERE disk collection sets interesting targets for future observations: the JWST, or the Extremely Large Telescope (ELT) currently under construction by ESO should allow astronomers to produce images of the planets that create these structures.
Background information
The results described here have been published as Natalia Engler et al., “Characterization of debris disks observed with SPHERE,” in the journal Astronomy and Astrophysics. DOI: 10.1051/0004-6361/202554953
The MPIA researchers involved are Gaël Chauvin, Thomas Henning, Samantha Brown, Matthias Samland, and Markus Feldt, in collaboration with Natalia Engler (ETH Zürich), Julien Milli (CNRS, IPAG, Université Grenoble Alpes), Nicole Pawellek (University of Vienna), Johan Olofsson (ESO), Anne-Lise Maire (CNRS, IPAG, Université Grenoble Alpes), and others
Journal
Astronomy and Astrophysics
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
Characterization of debris disks observed with SPHERE
Article Publication Date
3-Dec-2025
New funding to develop technology for first robots to weld in space
University of Leicester and welding specialist TWI Ltd collaborating on a robot-mounted arc-welding system
The University of Leicester is leading on the development of the UK’s first in-space robotic welding capability.
Scientists at Leicester, in partnership with welding specialist TWI Ltd, have secured funding through the UK Space Agency’s National Space Innovation Programme (NSIP) – Call 2 to develop ISPARK – the Intelligent SPace Arc-welding Robotic Kit.
Launched in April 2025, NSIP Call 2 attracted over 560 proposals, reflecting strong demand from UK industry and academia, with ISPARK among the 17 proposals selected.
Valued at £560,000 (including £485,000 from UKSA), ISPARK will develop ultimately a robot-mounted arc-welding system for in-space repair, joining and future orbital manufacturing. It directly supports the ambitions set out in the UK’s National Space Strategy and in the ISAM (In-Space Servicing, Assembly and Manufacturing) roadmap.
Welding in space faces extreme challenges such as vacuum, microgravity, thermal instability, and the danger and intense physical demands placed on astronauts. These barriers mean that space welding remains extremely rare and technologically difficult. This project develops a new, space-qualified robotic welding capability to overcome these challenges and enable autonomous in-orbit repair and manufacturing.
The welder will undergo trials in vacuum to check its performance which will be simulated by and checked against digital-twin modelling, helping to validate key technologies ahead of eventual use in the far more complex thermal, radiative and dynamic conditions of real spaceflight.
The ISPARK project combines the University’s expertise in AI-powered robotics, autonomous control, space engineering and digital-twin weld modelling with TWI’s international leadership in welding and materials joining technologies. It places Leicester at the forefront of the UK’s growing ISAM ecosystem, building on its contribution and involvement in more than 90 space missions over six decades and reinforcing its commitment to enabling the next generation of UK space innovation.
Principal Investigator Dr Daniel Zhou Hao, from the University of Leicester School of Computing and Mathematical Sciences, said: “ISPARK advances the UK’s and the world’s capability for in-space repair and manufacturing. By combining Leicester’s strengths in AI robotics and space engineering with TWI’s world-leading welding expertise, we are developing an enabling technology that could redefine how large structures are built and maintained in orbit.”
Dr Nick Ludford from TWI added:“TWI is pleased to be partnering with the University of Leicester on this pioneering effort. Applying advanced welding technologies to the challenges of space is a natural extension of our expertise, and ISPARK provides a unique opportunity to help develop a capability that will be vital for future in-orbit repair and construction.”
Professor Dirk Schaefer, Pro-Vice-Chancellor and Head of the University of Leicester College of Science and Engineering, said: “This award underscores the University of Leicester’s commitment to shaping the future of sustainable space operations and advanced manufacturing. ISPARK exemplifies the collaborative strength of Space Park Leicester, bringing together expertise from across the College of Science and Engineering and beyond, supported by strong industrial partnerships such as our collaboration with TWI.
“Developing the UK’s first in-space robotic welding capability is not only a scientific and engineering milestone, it also supports a more responsible and resilient space economy - where repairing, adapting and eventually manufacturing structures in orbit will reduce waste, extend mission lifetimes and enable new possibilities for sustainable exploration. As the UK continues to strengthen its position in the global ISAM landscape, we are proud to contribute knowledge, talent and innovation to a programme that pushes the boundaries of what is possible both in orbit and on Earth.”
The UK Space Agency has announced £17 million for seventeen UK space projects through its National Space Innovation Programme (NSIP), unveiled today at Space Comm Expo in Glasgow.
The selected projects span five strategic themes critical to the UK’s space ambitions: space domain awareness, in-orbit servicing and manufacturing, Earth observation, satellite communications, and position, navigation and timing.
Together, these projects will deliver transformative technologies to enhance climate monitoring, improve connectivity, enable sustainable satellite operations, and strengthen national security. From quantum communications and robotic servicing tools to AI-powered pollution tracking and refuellable propulsion systems, these innovations will help build a resilient, competitive UK space sector.
Space Minister Liz Lloyd said: “Space technology benefits people’s lives every day - from checking the weather to navigating your car journey home from work. This funding backs the brilliant UK innovators developing the next generation of space technology.
“By supporting our space sector, we’re strengthening the UK’s position as a world leader in space innovation and building technologies that will benefit people across the country for years to come.”
Concept art of the robot-mounted arc-welding system. Credit: ISPARK
Credit
Credit: ISPARK
Members of the ISPARK project team from the University of Leicester and TWI.
