SPACE/COSMOS
Safer space travel — Cosmic ray simulator at GSI/FAIR
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ESA astronaut Hans Schlegel outside the International Space Station ISS. In space, astronauts are exposed to cosmic radiation.
view moreCredit: © NASA
Cosmic rays are one of the greatest challenges for space travel and pose a considerable risk to humans and materials. For the first time on European soil, an international research team in collaboration with the European Space Agency (ESA) has succeeded in providing a simulator for Galactic Cosmic Rays at the GSI/FAIR accelerator facility in Darmstadt, Germany. The results have been published in two articles in the journal Life Sciences in Space Research.
Outside of Earth’s protective magnetic field, astronauts and spacecraft are exposed to cosmic radiation. Next to solar particles, Galactic Cosmic Rays (GCRs) are the main component. These are high-energy particles originating from outside our solar system, for example from supernovae or other explosive events within the Milky Way. GCRs consist mainly of protons and helium nuclei, but also other high-charge and high-energy particles (HZE), which contribute significantly to the radiation exposure of astronauts.
Estimates show that in space, every cell in an astronaut’s body is traversed by a proton every few days, by helium nuclei every few weeks, and by HZE particles every few months. In addition, neutrons and fragments are created when the particles pass through the shielding of a spacecraft. This can be particularly problematic during long-term missions to the Moon or to Mars, where significantly higher exposure levels are to be expected than in Low Earth Orbit.
GCRs are therefore the most significant long-term health risk for astronauts and can lead to cancer, degenerative cell effects, or disorders of the central nervous system. They also pose a threat to the electronic systems in spacecraft. Understanding and mitigating these risks is essential for a safe and sustainable human presence in space. Research on GCRs can only be conducted directly in space or with the aid of high-energy heavy ion accelerators like they are available at GSI/FAIR.
“Until now, there has been no reliable way to simulate GCRs in Europe,” explains Marco Durante, professor at the Technical University of Darmstadt and head of GSI/FAIR’s research department Biophysics. “That’s why our research team, with the support of our ESA partners, developed a simulator for GCRs and put it into operation at GSI/FAIR as part of the FAIR Phase 0 experiment program. This enables researchers to better understand the doses that affect technical components and human tissue and how these effects can be controlled or limited in a targeted approach.”
For this purpose, the researchers of the Space Radiation Physics group, led by Dr. Christoph Schuy of the Biophysics department, employ the unique GSI accelerators, which deliver high-energy ion beams of all elements occurring naturally on Earth. The GCR simulator is based on a hybrid, active-passive method: the energy of a primary beam of iron ions is actively varied before hitting passive beam modulators — a well-known and proven method from particle therapy. The geometry, material, composition, and thickness of the modulators are optimized to create a deep space radiation environment analog.
“Our results show good agreement with the values known from space missions. This technique can be used to generate a mixed radiation field that replicates the GCR exposure in a lightly shielded habitat like a spacecraft. In the future, we want to make the GCR simulator available to scientists for further space radiation research,” says Schuy. “True to our claim, we bring the Universe to the lab with this achievement.”
With the GCR simulator at GSI, supported by ESA, now a second possibility to study GCRs exists in the world — in addition to the simulator at the Brookhaven National Laboratory, USA, supported by NASA. Both provide beams with a maximal energy of one gigaelectronvolt per nucleon. The accelerator center FAIR (Facility for Antiproton and Ion Research), which is currently under construction at GSI in international collaboration, offers enhanced future perspectives. At FAIR, the energy will reach ten gigaelectronvolt per nucleon, making the GCR simulator in Darmstadt the most accurate worldwide.
GSI/FAIR and ESA have been working closely together for many years, using ion accelerators for the investigation of biological effects of cosmic radiation and finding solutions to protect astronauts. A simulator for Solar Particle Events (SPEs) based on modulators for tumor therapy is already available. Both institutions also jointly organize the annual “ESA-FAIR Space Radiation School” to give students an insight into the fundamentals of biophysics with heavy ions for both terrestrial and space applications. The next school will take place in August 2026, registration is open until April 12.''
In supernovae, Galactic Cosmic Rays are produced.
Credit
© X-ray: NASA/CXC/SAO; Infrared: NASA/ESA/CSA/STScI/D. Milisavljevic (Purdue Univ.), I. De Looze (UGent), T. Temim (Princeton Univ.); Image Processing: NASA/CXC/SAO/J. Major, J. Schmidt and K. Arcand
The GCR simulator is based on a hybrid, active-passive method: the energy of a primary beam of iron ions is actively varied before hitting passive beam modulators — a well-known and proven method from particle therapy. The geometry, material, composition, and thickness of the modulators are optimized to create a deep space radiation environment analog.
Credit
© GSI/FAIR
Postdoc Dr. Enrico Pierobon (left) and PhD-student Luca Lunati from GSI/FAIR Biophysics mount a microdosimeter on a robotic arm.
Credit
© A. Dörr, GSI/FAIR
Experimental setup of the GCR simulator at GSI/FAIR
Credit
© E. Pierobon, GSI/FAIR
From left. Marie Schumacher, Luca Lunati, Dr. Christoph Schuy, Prof. Dr. Marco Durante, Dr. Tim Wagner, Dr. Enrico Pierobon
Credit
© A. Dörr, GSI/FAIR
Journal
Life Sciences in Space Research
Method of Research
Experimental study
Article Title
Hybrid active–passive Galactic Cosmic Ray simulator: In-silico design and optimization
Conditions suitable for life on distant moons
Hydrogen atmosphere could keep exomoons habitable for billions of years
Liquid water is considered essential for life. Surprisingly, however, stable conditions that are conducive to life could exist far from any sun. A research team from the Excellence Cluster ORIGINS at LMU and the Max Planck Institute for Extraterrestrial Physics (MPE) has shown that moons around free-floating planets can keep their water oceans liquid for up to 4.3 billion years by virtue of dense hydrogen atmospheres and tidal heating – that is to say, for almost as long as the Earth has existed and sufficient time for complex life to develop.
Planetary systems often form under unstable conditions. If young planets come too close, they can fling each other out of their orbits. This creates free-floating planets (FFPs), which wander through the galaxy without a parent star. An earlier study by LMU physicist Dr. Giulia Roccetti had shown that gas giants ejected in this way do not necessarily lose all of their moons in the process.
Tidal heating keeps oceans liquid
The ejection does, however, alter the orbits of the moons. They become highly elliptical, such that their distance from the planet constantly changes. The resulting tidal forces rhythmically deform the lunar body, compress its interior, and generate heat through friction. This tidal heating can be sufficient to maintain oceans of liquid water on the surface – even without the energy of a star, and in the cold of interstellar space.
Hydrogen as stable heat trap
The atmosphere determines whether this heat is retained at the surface. On Earth, carbon dioxide functions as an effective greenhouse gas. Earlier studies had demonstrated that carbon dioxide could stabilize life-friendly conditions on exomoons for periods of up to 1.6 billion years. Under the extremely low temperatures of free-floating systems, however, carbon dioxide would condense, causing the atmosphere to lose its protective effect and allowing heat to escape.
And so the research team from the fields of astrophysics, biophysics, and astrochemistry investigated hydrogen-rich atmospheres as alternative heat traps. Although molecular hydrogen is largely transparent to infrared radiation, a crucial physical effect arises under high pressures: collision-induced absorption. In this process, colliding hydrogen molecules form transient complexes that can absorb thermal radiation and retain it in the atmosphere. At the same time, hydrogen remains stable even at very low temperatures.
Parallels to early Earth
The findings also furnish new clues to the origin of life. “Our collaboration with the team of Professor Dieter Braun helped us recognize that the cradle of life does not necessarily require a sun,” says David Dahlbüdding, doctoral researcher at LMU and lead author of the study. “We discovered a clear connection between these distant moons and the early Earth, where high concentrations of hydrogen through asteroid impacts could have created the conditions for life.”
Tidal forces could not only supply heat, but also drive processes of chemical development. Periodic deformation gives rise to local wet-dry cycles, in which water evaporates and then condenses again. Such cycles are considered an important mechanism for the formation of complex molecules and could facilitate crucial steps on the path to the emergence of life.
Moons hospitable to life in interstellar space
Free-floating planets are thought to be common. According to estimates, there could be as many of these ‘nomadic’ planets in the Milky Way as there are stars. Their moons could provide stable habitats for long periods of time. The new findings could thus significantly broaden the spectrum of possible environments that could harbor life – and show that life could arise and endure even in the darkest regions of the galaxy.
Article Title
Habitability of Tidally Heated H2-Dominated Exomoons around Free-Floating Planets
UCSB researcher bridges the worlds of general relativity and supernova astrophysics
Magnetars power anomalously bright supernovae
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A spinning magnetar twists space-time itself, causing the disk of material around it to wobble and produce the ultra-bright flashes of this peculiar kind of supernova.
view moreCredit: Joseph Farah and Curtis McCully of LCO
(Santa Barbara, Calif.) — For decades, astronomers have used distant supernovae as cosmic lighthouses to test fundamental physics and to measure the universe. For Joseph Farah, a fifth-year graduate student at UC Santa Barbara, one particular supernova began to signal something never seen before: a “chirp.”
In a groundbreaking paper accepted to the journal Nature, Farah and a team of international researchers, including his advisor Andy Howell, who leads the supernova group at Las Cumbres Observatory (LCO), announce the discovery of a superluminous supernova (SN 2024afav) whose erratic behavior has confirmed a long-standing theory of stellar death. By applying the principles of general relativity to the explosive death of a massive star, the team has provided an explanation for the unusual behavior of these ultra-bright events.
The mystery of the bumps
When a massive star runs out of fuel, its core collapses and the star dies in a spectacular explosion called a supernova. Most supernovae follow a predictable evolution, brightening and fading in a smooth arc. While ordinary supernovae are already bright enough to outshine their host galaxies, a rare class of supernovae has been discovered in recent years which are 10 to 100 times brighter: superluminous supernova whose power mechanism remains unknown. These hyper-bright explosions often have mysterious undulations, temporary surges that defy expectations and point to hidden physics inside the expanding supernova.
The origin of the overbrightness and bumps is hotly debated. One possibility is that superluminous supernovae are powered from within. The violent core collapse is theorized to forge a neutron star, an ultra-dense stellar remnant, which pours energy into the expanding supernova, increasing its brightness. Another school of thought suggests that the unusual characteristics stem from the supernova shock slamming into layers of gas clumped around the star. As the blast wave crashes into this surrounding material, it might briefly brighten the supernova again.
Scientists at LCO observed that SN 2024afav — located roughly a billion light-years away — displayed a strange sequence of “bumps” or modulations in its brightness. With SN 2024afav, Farah noticed a pattern that no random interactions could explain: The bumps had a clearly sinusoidal, periodic shape — and that period was getting rapidly shorter. For the first time, a supernova was displaying a quasi-periodic signal with an increasing frequency, generating a “chirp” reminiscent of the gravitational wave signals produced by merging black holes.
“There was just no existing model that could explain a pattern of bumps that get faster in time,” said Farah. “I started thinking about ways this could happen, because the signal seemed too structured to be due to random interactions.”
A magnetar under the hood
Farah’s breakthrough thinking came from an unlikely source: a General Relativity class he was auditing at the time with leading relativist and UCSB Professor Gary Horowitz. Farah hypothesized that the supernova had left behind a magnetar, a rapidly spinning neutron star with a massive magnetic field. In the existing theory, a magnetar can power a supernova like a battery, pumping in energy from within, leading to an ultra-bright and smooth rise and fall. But this theory can’t explain the bumps, which could be caused by anything from interactions with surrounding material to unexplained deviations in the power output of the magnetar.
According to Farah’s model, some material from the explosion fell back toward the magnetar, forming a tilted accretion disk. Because of a General Relativity effect known as Lense-Thirring precession, the fabric of space-time itself is twisted by the spinning magnetar, causing the disk to wobble. As the disk precessed, it periodically blocked and reflected light from the magnetar, turning the whole system into a strobing cosmic lighthouse. The precession timescale decreases with the radius of the disk; so as the disk slides inward towards the magnetar, the disk wobbles faster, creating the “chirp” observed by telescopes on Earth.
Lense-Thirring precession isn’t the only effect that can make a disk wobble. Working with theorist Logan Prust (a former postdoctoral scholar at UCSB’s Kavli Institute for Theoretical Physics), Farah and his team investigated several alternatives. What makes SN 2024afav unique — and a particularly effective test bed for these theories — is that any model needs to explain both the period and the period rate-of-change observed in the data. “We tested several ideas, including purely Newtonian effects and precession driven by the magnetar’s magnetic fields, but only Lense-Thirring precession matched the timing perfectly,” Farah explained. “It is the first time General Relativity has been invoked to describe the mechanics of a supernova.”
A Victory for Global Observation
The discovery was a “mad dash” involving a global network of telescopes. While the ATLAS survey discovered the initial flash in December 2024, the LCO in Goleta played a pivotal role, tracking the event for over 200 days. During this extended campaign, the team took maximal advantage of the full suite of LCO’s instruments and ability to near-continuously survey any target. Observation parameters were adjusted on-the-fly to capture even the faintest bumps in SN 2024afav’s evolution.
“This is a major victory for LCO,” said Farah. “The uniquely pristine and high-cadence LCO data allowed us to predict future bumps and the ability to dynamically adjust the campaign on a dime let us check our predictions in real-time. When the predictions started coming true, we knew we were watching something special.”
The paper is being hailed as a breakthrough for two reasons. As the first observed “chirp” in a supernova, it identifies a new class of observational phenomena in exploding stars. It also provides the first unambiguous confirmation of the magnetar model for superluminous supernovae, transforming the model from one of several competing hypotheses into an observationally confirmed mechanism.
The Next Frontier
Farah, who is set to defend his Ph.D. thesis at UCSB this May, will continue his work as a Miller Fellow of the Miller Institute for Basic Science at UC Berkeley, working alongside Professor Dan Kasen — the physicist who originally proposed the magnetar model.
Farah’s advisor, Andy Howell, emphasized the importance of the breakthrough: “I was part of the discovery of superluminous supernovae almost 20 years ago, and at first we didn’t know what they were. Then the magnetar model was developed and it seemed like it could explain the astounding energies needed, but not the bumps.
“Now, I think Joseph has found the smoking gun,” Howell continued, “and he’s tied the bumps into the magnetar model, and explained everything with the best-tested theory in astrophysics – General Relativity. It is incredibly elegant.”
Farah expects to find dozens more of these “chirping” supernovae as the Vera C. Rubin Observatory in Chile prepares to come online and begin the most comprehensive survey of the night sky. The new facility will produce 10 terabytes of data every night throughout a ten-year initiative. “This is the most exciting thing I have ever had the privilege to be a part of. This is the science I dreamed of as a kid,” Farah said. “It’s the universe telling us out loud and in our face that we don’t fully understand it yet, and challenging us to explain it.”
Journal
Nature
Astronomers capture birth of a magnetar, confirming link to some of universe’s brightest exploding stars
A UC Berkeley theorist proposed that highly magnetized, spinning neutron stars were the power source behind superluminous supernovae. A recent supernova provided the smoking gun.
University of California - Berkeley
image:
Artist’s conception of a magnetar surrounded by an accretion disk that is wobbling, or precessing, because of the effects of general relativity. Some models of magnetars suggest that high-speed jets of charged particles emanate from the magnetar along its rotation axis.
view moreCredit: Joseph Farah and Curtis McCully, Las Cumbres Observatory
Astronomers have for the first time seen the birth of a magnetar — a highly magnetized, spinning neutron star — and confirmed that it’s the power source behind some of the brightest exploding stars in the cosmos.
The finding corroborates a theory proposed by a UC Berkeley physicist 16 years ago and establishes a new phenomenon in exploding stars: supernovae with a “chirp” in their light curve that is caused by general relativity. A paper describing the phenomenon was published today (March 11) in the journal Nature.
Superluminous supernovae — which can be 10 or more times brighter than run-of-the-mill supernovae — have puzzled astronomers since their discovery in the early 2000s. They were thought to result from the explosion of very massive stars, perhaps 25 times the mass of our sun, but they stayed bright much longer than would be expected when a star’s iron core collapses and its outer layers are subsequently blown off.
In 2010, Dan Kasen, now a UC Berkeley theoretical astrophysicist and professor of physics, was the first to propose that a magnetar was powering the long-lasting glow. According to the theory, coauthored with Lars Bildsten and suggested independently by Stanford Woosley of UC Santa Cruz, when a massive star collapses at the end of its lifetime, it crushes much of its mass into a very compact neutron star — a fate just short of collapsing to a black hole. If the star originally had a very strong magnetic field, it would have been amplified during magnetar formation, producing a field 100 to 1,000 times stronger than that of normal spinning neutron stars — so-called pulsars. Pulsars and their highly magnetized big brothers, magnetars, are only about 10 miles in diameter but, in their youth, can spin more than 1,000 times per second.
As the magnetar spins, the spinning magnetic field can accelerate charged particles that slam into the debris from the expanding supernova, increasing its brightness. Magnetars are also thought to be the source of fast radio bursts.
Graduate student Joseph Farah of UC Santa Barbara and Las Cumbres Observatory (LCO), who will come to UC Berkeley this fall as a Miller Postdoctoral Fellow in Kasen’s group, confirmed the connection between magnetars and Type I superluminous supernovae (SLSNe-I) after analyzing data from a 2024 supernova dubbed SN 2024afav. In the Nature paper, Farah and his colleagues proposed a general relativistic explanation for unusual bumps in the light curve of this supernova — what they call a chirp — that conclusively connect it to a magnetar.
“What’s really exciting is that this is definitive evidence for a magnetar forming as the result of a superluminous supernova core collapse,” said Alex Filippenko, a UC Berkeley distinguished professor of astronomy who is a coauthor of the paper and one of Farah’s soon-to-be mentors. “The basis of Dan Kasen and Stan Woosley’s model is that all you need is the energy of the magnetar deep within and a good fraction of it will get absorbed, and that'll explain why the thing is superluminous. What had not been demonstrated was that a magnetar did in fact form in the middle of the supernova, and that's what Joseph's paper shows.”
“For years the magnetar idea has felt almost like a theorist’s magic trick — hiding a powerful engine behind layers of supernova debris. It was a natural explanation for the extraordinary brightness of these explosions, but we couldn’t see it directly,” Kasen said. “The chirp in this supernova signal is like that engine pulling back the curtain and revealing that it’s really there.”
Distant discovery
After SN 2024afav was discovered in December 2024, Las Cumbres Observatory — a network of 27 telescopes around the world — tracked it and measured its brightness for more than 200 days. The exploding star was located about a billion light-years from Earth.
Farah, working with UCSB astronomer Andy Howell, noticed that after the brightness peaked about 50 days after the explosion, it didn’t gradually fade away like typical supernovae. Instead, its brightness slowly oscillated downward, with the period of the oscillations gradually shortening, producing a series of four bumps. He compared this to a sound gradually increasing in frequency, sounding much like a bird chirp.
Previous superluminous supernovae were known to have a couple of bumps in their decaying light curve, which some interpreted as the supernova shock colliding with layers of gas clumped around the star, briefly brightening it. But no one had observed as many as four.
According to Farah’s model, some material from the SN 2024afav explosion fell back toward the magnetar, forming a disk of matter called an accretion disk. Since material around the magnetar is unlikely to be symmetric, the accretion disk would not be symmetric about the spinning neutron star either, leading to a misalignment of the magnetar spin axis and the spin axis of the accretion disk.
Because general relativity states that a spinning mass drags space-time with it, the spinning magnetar would produce an effect known as Lense-Thirring precession — that is, it would make the misaligned disk wobble. A wobbling disk could periodically block and reflect light from the magnetar, turning the whole system into a strobing cosmic lighthouse. The time for this to repeat decreases with the radius of the disk, so as the disk slides inward toward the magnetar, it wobbles faster, causing the light to oscillate more rapidly as it fades, creating the "chirp" observed by telescopes on Earth.
"We tested several ideas, including purely Newtonian effects and precession driven by the magnetar’s magnetic fields, but only Lense-Thirring precession matched the timing perfectly," Farah said. "It is the first time general relativity has been needed to describe the mechanics of a supernova."
The astronomers also used observational data to estimate the neutron star’s spin period — 4.2 milliseconds — and magnetic field: about 300 trillion times that of Earth. Both are hallmarks of a magnetar.
“I think Joseph has found the smoking gun,” said Howell, a senior scientist at LCO and UCSB adjunct professor of physics. “He’s tied the bumps into the magnetar model and explained everything with the best-tested theory in astrophysics — general relativity. It is incredibly elegant.” Filippenko added, “To see a clear effect of Einstein’s general theory of relativity is always exciting, but seeing it for the first time in a supernova is especially rewarding.”
Filippenko cautioned that Farah’s conclusion does not mean that all superluminous supernovae are powered by magnetars. There’s also the alternative theory: that the shock wave from the exploding star hits material surrounding it, bumping its brightness up a bit. Moreover, Kasen has proposed that if the core collapse of a star results in a black hole, that could also power a brighter supernova and, if it had a misaligned accretion disk, produce bumps in the light curve.
“We don't know what fraction of Type I superluminous supernovae might be powered by circumstellar material, but it’s definitely a smaller fraction than we previously thought, because this discovery clearly accounts for some of them,” Filippenko said.
Farah expects to find dozens more of these "chirping" supernovae as the Vera C. Rubin Observatory prepares to come online and begin the most comprehensive survey of the night sky to date.
"This is the most exciting thing I have ever had the privilege to be a part of. This is the science I dreamed of as a kid," Farah said. "It’s the universe telling us out loud and in our face that we don’t fully understand it yet, and challenging us to explain it."
Howell, Logan Prust, now at the Flatiron Institute in New York, and Yuan Qi Ni of UCSB contributed equally to the work. Filippenko acknowledges financial support from Christopher R. Redlich and many other donors.
Journal
Nature
Article Title
Lense–Thirring precessing magnetar engine drives a superluminous supernova
Article Publication Date
11-Mar-2026
