When chunks of space debris make their fiery descent through the Earth’s atmosphere, they leave a trail of shock waves in their wake. Geophysicists have now found a way to exploit this phenomenon, using open-source seismic data from a network of earthquake sensors to monitor the waves produced by China’s Shenzhou-15 module as it fell to Earth in April 2024. The method is valuable, they say, because it makes it possible to follow debris – which can be hazardous to humans and animals – in near-real time as they travel towards the surface.

“We’re at the situation today where more and more spacecraft are re-entering the Earth’s atmosphere on a daily basis,” says team member Benjamin Fernando, a postdoctoral researcher at Johns Hopkins University in the US. “The problem is that we don’t necessarily know what happens to the fragments this space debris produces – whether they all break up in the atmosphere or if some of them reach the ground.”

Piggybacking on a network of earthquake sensors

As the Shenzhou-15 module re-entered the atmosphere, it began to disintegrate, producing debris that travelled at supersonic speeds (between Mach 25‒30) over the US cities of Santa Barbara, California and Las Vegas, Nevada. The resulting sonic booms produced vibrations strong enough to be picked up by a network of 125 seismic stations spread over Nevada and Southern California.

Fernando and his colleague Constantinos Charalambous at Imperial College London in the UK used freely available data from these stations to measure the arrival times of the largest sonic boom signals. Based on these data, they produced a contour map of the path the debris took and the direction in which it propagated. They also determined the altitude of the module as it travelled by using ratios of the speed of sound to the apparent speed of the incident wavefront its supersonic flight generated as it passed over the seismic stations. Finally, they used a best-fit seismic inversion model to estimate where remnants of the module may have landed and the speed at which they travelled over the ground.

The analyses revealed that the module travelled roughly 20-30 kilometres south of the trajectory that US Space Command had predicted based on measurements of the module’s orbit alone. The seismic data also showed that the module gradually disintegrated into smaller pieces rather than undergoing a single explosive disassembly.

Advantages of accurate tracking

To obtain an estimate of the object’s trajectory within seconds or minutes, the researchers had to simplify their calculations by ignoring the effects of wind and temperature variations in the lower troposphere (the lowest layer of the Earth’s atmosphere). This simplification also did away with the need to simulate the path of wave signals through the atmosphere, which was essential for previous techniques that relied on radar data to follow objects decaying in low Earth orbit. These older techniques, Fernando adds, produced predictions of the objects’ landing sites that could, in the worst cases, be out by thousands of kilometres.

The availability of accurate, near-real time debris tracking could be particularly helpful in cases where the debris is potentially harmful. As an example, Fernando cites an incident in 1996, when debris from the Russian Mars 96 spacecraft fell out of orbit. “People thought it burned up and [that] its radioactive power source landed intact in the ocean,” he says. “They tried to track it at the time, but its location was never confirmed. More recently, a group of scientists found artificial plutonium in a glacier in Chile that they believe is evidence the power source burst open during the descent and contaminated the area.”

Though Fernando emphasizes that it’s rare for debris to contain radioactive material, he argues “we’d benefit from having additional tracking tools” when it does.

Towards an automated algorithm for trajectory reconstruction

Fernando had previously used seismometers to track natural meteoroids, comets and asteroids on both Earth and Mars. In the latter case, he used data from InSight, a NASA Mars mission equipped with a seismometer.

“The meteoroids hitting the Red Planet were a really good seismic source for us,” he explains. “We detected the sonic booms from them breaking up and, occasionally, would actually detect the impact of them hitting the ground. We realized that we could actually apply those same techniques to studying space debris on Earth.

“This is an excellent example of a technique that we really perfected the expertise for a planetary science kind of pure science application. And then we were able to apply it to a really relevant, challenging problem here on Earth,” he tells Physics World.

The scientists say that in the longer term, they hope to develop an algorithm that automatically reconstructs the trajectory of an object. “At the moment, we’re having to find the sonic boons and analyse the data ‘by hand’,” Fernando says. “That’s obviously very slow, even though we’re getting better.”

A better solution, Fernando continues, would be to develop a machine learning tool that can find sonic booms in the data when a re-entry is expected, and then use those data to reconstruct the trajectory of an object. They are currently applying for funding to explore this option in a follow-up study.

Beyond that, there’s also the question of what to do with the data once they have it. “Who would we send the data to?” Fernando asks rhetorically. “Who needs to know about these events? If there’s a plane crash, hurricane, or similar, there are already good international frameworks in place for dealing with these events. It’s not clear to me, however, that such a framework for dealing with space debris has caught up with reality – either in terms of regulations or the response when such an event does happen.”

The current research is described in Science.

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China took a major step forward in its lunar and human spaceflight programs late Tuesday with successful in-flight abort and rocket recovery tests.

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A proposed industrial-scale green hydrogen and ammonia project in Chile that astronomers warned could cause “irreparable damage” to the clearest skies in the world has been cancelled. The decision by AES Andes, a subsidiary of the US power company AES Corporation, to shelve plans for the INNA complex has been welcomed by the European Southern Observatory (ESO).

AES Andes submitted an Environmental Impact Assessment for the green hydrogen project in December 2024. Expected to cover more than 3000 hectares, it would have been located just a few kilometres from ESO’s Paranal Observatory in Chile’s Atacama Desert, which is one of the world’s most important astronomical research sites due to its stable atmosphere and lack of light pollution.

That same month, ESO conducted its own impact assessment, concluding that INNA would increase light pollution above Paranal’s Very Large Telescope by at least 35% and by more than 50% above the southern site of the Cherenkov Telescope Array Observatory (CTAO).

Once built, the CTAO will be the world’s most powerful ground-based observatory for very high-energy gamma-ray astronomy.

ESO director general Xavier Barcons had warned that the hydrogen project would have posed a major threat to “the performance of the most advanced astronomical facilities anywhere in the world”.

On 23 January, however, AES Andes announced that it will discontinue plans to develop the INNA complex. The firm stated that after a review of its project portfolio it had chosen to instead focus on renewable energy and energy storage. On 6 February, AES Andes sent a letter to Chile’s Environmental Assessment Service requesting that INNA is not evaluated, which formally confirmed the end of the project.

Barcons says that ESO is “relieved” about the decision, adding that the case highlights the urgent need to establish clear protection measures in the areas around astronomical observatories.

Barcons notes that green-energy projects as well as other industrial projects can be “fully compatible” with astronomical observatories along as the facilities are located at sufficient distances away.

Romano Corradi, director of the Gran Telescopio Canarias, which is located at the Roque de los Muchachos Observatory, La Palma, Spain, told Physics World that he was “delighted” with the decision.

Corradi adds that while it is unclear if preserving the night-sky darkness of the region was a relevant factor for the decision to cancel the project, he hopes that global pressure to defend the dark skies played a role.

The post ‘Relief’ as industrial megaproject in Chile that threatened world’s darkest skies is cancelled appeared first on Physics World.

High-energy heavy-nuclei collisions, conducted at particle colliders such as CERN’s Large Hadron Collider (LHC) and BNL’s Relativistic Heavy Ion Collider (RHIC) are able to produce a state of matter called a quark-gluon plasma (QGP).

A QGP is believed to have existed just after the Big Bang. The building blocks of protons and neutrons – quarks and gluons – were not confined inside particles as usual but instead formed a hot, dense, strongly interacting soup.

Studying this state of matter helps us understand the strong nuclear force, the early universe, and how matter evolved into the forms we see today.

In order to understand QGP created in a particle collider you need to know the initial conditions. In this case that is the shape and structure of the heavy nuclei that collided.

A major complicating factor here is that most atomic nuclei are deformed. They are not spherical but rather squashed and ellipsoidal or even pear-shaped.

Collisions of deformed nuclei with different orientations brings in a large amount of randomness and therefore hinders our ability to describe the initial conditions of the QGP.

A new method called imaging-by-smashing was developed by the STAR experiment at RHIC, where atomic nuclei are smashed together at extremely high speeds. By studying the patterns in the debris from these collisions, researchers can infer the original shape of the nuclei.

In this latest study, they compared collisions between two types of nuclei: uranium-238, which has a strongly deformed shape, and gold-197, which is nearly spherical.

The differences between uranium and gold helped isolate the effects of uranium’s deformation. Their results matched predictions from advanced hydrodynamic simulations and earlier low-energy experiments.

Most interestingly, they found hints that uranium might possess a pear-like (octupole) shape, in addition to its dominant football-like (quadrupole) shape. This feature had not previously been observed in high-energy collisions

This method is still new, but in the future, it could give us key insights nuclear structure throughout the periodic table. These measurements probe nuclei at energy scales orders of magnitudes higher than traditional methods, potentially revealing how nuclear structure evolves across very different energy regimes.

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In quantum mechanics, a quantum state is a complete description of a system’s physical properties.

If the system changes slowly and returns to its original physical configuration, then its quantum state also returns to its original form except for a phase factor.

In a pioneering work in 1984, physicist Michael Berry discovered that this factor can be separated into two parts: the dynamic and the geometric phase.

The usual dynamic phase depends on energy and time and was already well understood. The new part, the geometric phase (or Berry phase after its discoverer) arises purely from the geometry of the path that the state takes through parameter space.

The Berry phase has profound implications across physics, appearing in phenomena like the quantum Hall effect, molecular dynamics, and polarised light. It reveals deep connections between geometry, topology, and physical observables.

In a recent paper, this concept was extended from wave evolution to certain wave scattering events, where waves bounce off or pass through materials and their properties shift.

In order to do this, the authors used a mathematical tool called a scattering matrix. The matrix encodes all the possible outcomes of a scattering process – reflection, transmission, or deflection -based on the system’s properties.

They showed that these wave shifts can also be split into dynamic and geometric parts. Importantly this splitting can be done in such a way that doesn’t depend on arbitrary choices (i.e., it’s gauge-invariant).

The team demonstrated their idea with known examples like light passing through a changing waveplate, beams reflecting off surfaces, and time delays in 1D systems.

Their approach is not only able to describe known phenomena, but also reveals new physical features, provides new insights, and uncovers previously unnoticed connections.

Going forward, identifying the geometric and dynamic origins of various scattering-induced shifts offers new ways to control wave-scattering phenomena.

This could have applications in photonics, imaging, quantum computing, and micromanipulation.

 

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As next-generation telescopes map this outer frontier, astronomers are bracing for discoveries that could reveal hidden planets, strange structures, and clues to the solar system’s chaotic youth.

Radiation therapy is usually delivered by prescribing the same radiation dose for each particular type of tumour. But this “one-size-fits-all” approach does not account for a tumour’s intrinsic radiosensitivity and heterogeneity and can lead to recurrence and treatment failure. Researchers in Sweden and Germany are now investigating whether biologically individualized radiotherapy plans, created using PET images of a patient’s tumour biology, can improve treatment outcomes.

The research team – headed up by Marta Lazzeroni from Stockholm University – studied 28 patients with advanced head-and-neck squamous cell carcinoma (HNSCC). All patients underwent two pre-treatment PET/CT scans, using ¹⁸F-fluoromisonidazole (FMISO) and ¹⁸F-FDG as tracers to respectively quantify radioresistance and tumour cellularity (the percentage of clonogenic cells) – both critical factors that influence treatment response.

“FMISO provides information on hypoxia-related radioresistance, but tumour control also strongly depends on the number of clonogenic cells, which is not captured by hypoxia imaging alone,” Lazzeroni explains. “To our knowledge, this is the first study to combine FMISO and FDG PET within a unified radiobiological framework to guide biologically individualized dose escalation.”

For each patient, the researchers used FMISO uptake to derive voxel-level maps of oxygen partial pressure (pO₂) in the tumour and define a hypoxic target volume (HTV). The FDG scans were used to estimate spatial variations in clonogenic tumour cell density, which directly influence the dose required to realise a given tumour control probability (TCP).

Based on individual tumour profiles, the team used automated planning to create volumetric-modulated arc therapy plans comprising 35 fractions with an integrated boost. The plans delivered escalated dose to radioresistant subvolumes (the HTV), while maintaining clinically acceptable sparing of organs-at-risk. The PET datasets were used to calculate the prescribed dose required to achieve a TCP of 95%.

Meeting clinical feasibility

The automated planning pipeline achieved high-quality treatment plans for all patients without manual intervention. The average EQD2 (the dose delivered in 2 Gy fractions that’s biologically equivalent to the total dose) to the HTV was boosted to 81±3.2 Gy, and all 28 plans met the clinical constraints for protecting the brainstem, spinal cord and mandible. Parotid glands were spared in 75% of cases, with the remainder being glands that overlapped the target.

Lazzeroni and colleagues suggest that these results confirm the overall clinical feasibility of their personalized dose-escalation strategy and demonstrate how biology-guided prescriptions could be integrated into existing treatment planning workflows.

The researchers also performed a radiobiologic evaluation of the treatment plans to see whether the optimized dose distribution achieved the desired target control. For this, they calculated the TCP based on the planned dose distribution, the PET-derived radioresistance data and clonogenic cell density maps. For all patients, the plans achieved model-predicted TCP values exceeding 90%, a notable improvement on tumour control rates reported in the clinical literature for HNSCC, which are typically around 60%.

The proposed strategy is based on pre-treatment PET images, but biological changes during treatment – including temporal and spatial variations in tumour hypoxia – could impact its effectiveness. In future, the researchers suggest that longitudinal imaging, such as PET/CT scans at weeks 3 and 5, could be used to monitor evolving tumour biology and inform adaptive replanning. This is particularly relevant in HNSCC, where tumour shrinkage and reoxygenation are common, and where updated imaging is required to determine whether dose escalation or de-escalation is appropriate to maintain tumour control and optimize normal tissue sparing.

The researchers point out that as the biology-guided dose prescriptions were planned but not delivered, prospective trials will be required to assess whether the observed dosimetric and biologic gains translate to improved patient outcomes.

“This study was designed as a feasibility and modelling investigation, and the next step is prospective clinical validation,” Lazzeroni tells Physics World. “Based on the promising results of this approach, prospective clinical trials are currently in the planning phase within the group led by Anca-L Grosu in Germany. These trials will focus on integrating longitudinal PET imaging during treatment to enable biologically adaptive radiotherapy.”

The results are published in the Journal of Nuclear Medicine.

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Unusual “hood” is the first known biological armor that protects against traumatic brain injury

Amazon received approval Feb. 10 to deploy thousands more broadband satellites, weeks after seeking relief from a July milestone for its first-generation network after reaching only about 11% of the required deployment.

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Iron salt toothpaste darkened pearly whites

Learn more about the Bergstrom site in Montana, which was abandoned by bison hunters in response to their changing climate.

Learn how a second pair of eyes helped this 518-million-year-old fish evade predators.

Manufacturers of small satellites that lack opportunities to build very large constellations say they are seeing growing interest from customers seeking smaller systems tailored to specific needs.

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Learn about the Amsterdam Island cows, who against all odds took over a subantarctic ocean island deep in the southern Indian Ocean.

“The NRO is always looking for innovative ways to bring on new partners,” said Chris Scolese, director of the NRO

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Learn more about Tyrannoroter heberti, a football-shaped land vertebrate who may have enjoyed snacking on plants.

Learn how an ancient fish gene was repurposed to shape the anatomy of human hands.

Learn how boar populations in Fukushima’s evacuation zone are evolving rapidly after mating with abandoned domesticated pigs.

Executives say customers care less about how data moves than what it enables

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MOUNTAIN VIEW, Calif. – Australia is applying space-related products and services to national and regional challenges through an independent not-for-profit organization, the Australasian Space Innovation Institute (ASII). ASII, which began operations in January, builds on the work of the SmartSat Cooperative Research Centre, a consortium established in 2019 to bolster research and development of space […]

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COO Mark Peller said ULA is aiming for between 18 and 22 launches in 2026

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MILAN — Bavarian Minister-President Markus Söder announced Feb. 4 that the German Aerospace Center (DLR) will receive 58 million euros ($69 million) to build a Human Exploration Control Center to support future robotic and human exploration missions. The total cost of the facility is 78 million euros and in addition to the Bavarian funding, DLR […]

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Are you speechless watching US figure skater Ilia Malinin on the ice? Science explains how it’s possible the Quad God can do more than four full rotations in the air.

The site Realfood.gov uses Elon Musk’s Grok chatbot to dispense nutrition information—some of which contradicts the government’s new guidelines.