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Photon collisions in dying stars could create neutrons for heavy elements

A model that could help explain how heavy elements are forged within collapsing stars has been unveiled by Matthew Mumpower at Los Alamos National Laboratory and colleagues in the US. The team suggests that energetic photons generated by newly forming black holes or neutron stars transmute protons within ejected stellar material into neutrons, thereby providing ideal conditions for heavy elements to form.

Astrophysicists believe that elements heavier than iron are created in violent processes such as the explosions of massive stars and the mergers of neutron stars. One way that this is thought to occur is the rapid neutron-capture process (r-process), whereby lighter nuclei created in stars capture neutrons in rapid succession. However, exactly where the r-process occurs is not well understood.

As Mumpower explains, the r-process must be occurring in environments where free neutrons are available in abundance. “But there’s a catch,” he says. “Free neutrons are unstable and decay in about 15 min. Only a few places in the universe have the right conditions to create and use these neutrons quickly enough. Identifying those places has been one of the toughest open questions in physics.”

Intense flashes of light

In their study, Mumpower’s team – which included researchers from the Los Alamos and Argonne national laboratories – looked at how lots of neutrons could be created within massive stars that are collapsing to become neutron stars or black holes. Their idea focuses on the intense flashes of light that are known to be emitted from the cores of these objects.

This radiation is emitted at wavelengths across the electromagnetic spectrum – including highly energetic gamma rays. Furthermore, the light is emitted along a pair of narrow jets, which blast outward above each pole of the star’s collapsing core. As they form, these jets plough through the envelope of stellar material surrounding the core, which had been previously ejected by the star. This is believed to create a “cocoon” of hot, dense material surrounding each jet.

In this environment, Mumpower’s team suggest that energetic photons in a jet collide with protons to create a neutron and a pion. Since these neutrons are have no electrical charge, many of them could dissolve into the cocoon, providing ideal conditions for the r-process to occur.

To test their hypothesis, the researchers carried out detailed computer simulations to predict the number of free neutrons entering the cocoon due to this process.

Gold and platinum

“We found that this light-based process can create a large number of neutrons,” Mumpower says. “There may be enough neutrons produced this way to build heavy elements, from gold and platinum all the way up to the heaviest elements in the periodic table – and maybe even beyond.”

If their model is correct, suggests that the origin of some heavy elements involves processes that are associated with the high-energy particle physics that is studied at facilities like the Large Hadron Collider.

“This process connects high-energy physics – which usually focuses on particles like quarks, with low-energy astrophysics – which studies stars and galaxies,” Mumpower says. “These are two areas that rarely intersect in the context of forming heavy elements.”

Kilonova explosions

The team’s findings also shed new light on some other astrophysical phenomena. “Our study offers a new explanation for why certain cosmic events, like long gamma-ray bursts, are often followed by kilonova explosions – the glow from the radioactive decay of freshly made heavy elements,” Mumpower continues. “It also helps explain why the pattern of heavy elements in old stars across the galaxy looks surprisingly similar.”

The findings could also improve our understanding of the chemical makeup of deep-sea deposits on Earth. The presence of both iron and plutonium in this material suggests that both elements may have been created in the same type of event, before coalescing into the newly forming Earth.

For now, the team will aim to strengthen their model through further simulations – which could better reproduce the complex, dynamic processes taking place as massive stars collapse.

The research is described in The Astrophysical Journal.

The post Photon collisions in dying stars could create neutrons for heavy elements appeared first on Physics World.

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Researchers claim Trump administration is conducting ‘a wholesale assault on science’

The US administration is carrying out “a wholesale assault on US science” that could hold back research in the country for several decades. That is the warning from more than 1900 members of the US National Academies of Sciences, Engineering, and Medicine, who have signed an open letter condemning the policies introduced by Donald Trump since he took up office on 20 January.

US universities are in the firing line of the Trump administration, which is seeking to revoke the visas of foreign students, threatening to withdraw grants and demanding control over academic syllabuses. “The voice of science must not be silenced,” the letter writers say. “We all benefit from science, and we all stand to lose if the nation’s research enterprise is destroyed.”

Particularly hard hit are the country’s eight Ivy League universities, which have been accused of downplaying antisemitism exhibited in campus demonstrations in support of Gaza. Columbia University in New York, for example, has been trying to regain $400m in federal funds that the Trump administration threatened to cancel.

Columbia initially reached an agreement with the government on issues such as banning facemasks on its campus and taking control of its department responsible for courses on the Middle East. But on 8 April, according to reports, the National Institutes of Health, under orders from the Department of Health and Human Services, blocked all of its grants to Columbia.

Harvard University, meanwhile, has announced plans to privately borrow $750m after the Trump administration announced that it would review $9bn in the university’s government funding. Brown University in Rhode Island faces a loss of $510m, while the government has suspended several dozen research grants for Princeton University.

The administration also continues to oppose the use of diversity, equity and inclusion (DEI) programmes in universities. The University of Pennsylvania, from which Donald Trump graduated, faces the suspension of $175m in grants for offences against the government’s DEI policy.

Brain drain

Researchers in medical and social sciences are bearing the brunt of government cuts, with physics departments seeing relatively little impact on staffing and recruitment so far. “Of course we are concerned,” Peter Littlewood, chair of the University of Chicago’s physics department, told Physics World. “Nonetheless, we have made a deliberate decision not to halt faculty recruiting and stand by all our PhD offers.”

David Hsieh, executive officer for physics at California Institute of Technology, told Physics World that his department has also not taken any action so far. “I am sure that each institution is preparing in ways that make the most sense for them,” he says. “But I am not aware of any collective response at the moment.”

Yet universities are already bracing themselves for a potential brain drain. “The faculty and postdoc market is international, and the current sentiment makes the US less attractive for reasons beyond just finance,” warns Littlewood at Chicago.

That sentiment is echoed by Maura Healey, governor of Massachusetts, who claims that Europe, the Middle East and China are already recruiting the state’s best and brightest. “[They’re saying] we’ll give you a lab; we’ll give you staff. We’re giving away assets to other countries instead of training them, growing them [and] supporting them here.”

Science agencies remain under pressure too. The Department of Government Efficiency, run by Elon Musk, has already  ended $420m in “unneeded” NASA contracts. The administration aims to cut the year’s National Science Foundation (NSF) construction budget, with data indicating that the agency has roughly halved its number of new grants since Trump became president.

Yet a threat to reduce the percentage of ancillary costs related to scientific grants appeared at least on hold, for now at least. “NSF awardees may continue to budget and charge indirect costs using either their federally negotiated indirect cost rate agreement or the “de minimis” rate of 15%, as authorized by the uniform guidance and other Federal regulations,” says an NSF spokesperson.

The post Researchers claim Trump administration is conducting ‘a wholesale assault on science’ appeared first on Physics World.

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Ultrashort electron beam sets new power record

Researchers at the SLAC National Accelerator Laboratory in the US have produced the world’s most powerful ultrashort electron beam to date, concentrating petawatt-level peak powers into femtosecond-long pulses at an energy of 10 GeV and a current of around 0.1 MA. According to officials at SLAC’s Facility for Advanced Accelerator Experimental Tests (FACET-II), the new beam could be used to study phenomena in materials science, quantum physics and even astrophysics that were not accessible before.

High-energy electron beams are routinely employed as powerful probes in several scientific fields. To produce them, accelerator facilities like SLAC use strong electric fields to accelerate, focus and compress bunches of electrons. This is not easy, because as electrons are accelerated and compressed, they emit radiation and lose energy, causing the beam’s quality to deteriorate.

An optimally compressed beam

To create their super-compressed ultrashort beam, researchers led by Claudio Emma at FACET-II used a laser to shape the electron bunch’s profile with millimetre-scale precision in the first 10 metres of the accelerator, when the beam’s energy is lowest. They then took this modulated electron beam and boosted its energy by a factor of 100 in a kilometre-long stretch of downstream accelerating cavities. The last step was to compress the beam by a factor of 1000 by using magnets to turn the beam’s millimetre-scale features into a micron-sized long current spike.

One of the biggest challenges, Emma says, was to optimise the laser-based modulation of the beam in tandem with the accelerating cavity and magnetic fields of the magnets to obtain the optimally compressed beam at the end of the accelerator. “This was a large parameter space to work in with lots of knobs to turn and it required careful iteration before an optimum was found,” Emma says.

Measuring the ultra-short electron bunches was also a challenge. “These are typically so intense that if you intercept them with, for example, scintillating screens (a typical technique used in accelerators to diagnose properties of the beam like its spot size or bunch length), the beam fields are so strong they can melt these screens,” Emma explains. “To overcome this, we had to use a series of indirect measurements (plasma ionisation and beam-based radiation) along with simulations to diagnose just how strongly compressed and powerful these beams were.”

Beam delivery

According to Emma, generating extremely compressed electron beams is one of the most important challenges facing accelerator and beam physicists today. “It was interesting for us to tackle this challenge at FACET-II, which is a facility designed specifically to do this kind of research on extreme beam manipulation,” he says.

The team has already delivered the new high-current beams to experimenters who work on probing and optimising the dynamics of plasma-based accelerators. Further down the line, they anticipate much wider applications. “In the future we imagine that we will attract interest from users in multiple fields, be they materials scientists, strong-field quantum physicists or astrophysicists, who want to use the beam as a strong relativistic ‘hammer’ to study and probe a variety of natural interactions with the unique tool that we can provide,” Emma tells Physics World.

The researchers’ next step will be to increase the beam’s current by another order of magnitude. “This additional leap will require the use of a different plasma-based compression technique, rather than the current laser-based approach, which we hope to demonstrate at FACET-II in the near future,” Emma reveals.

The present work is described in Physical Review Letters.

The post Ultrashort electron beam sets new power record appeared first on Physics World.

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Space Forge sees LEO as key to strengthening US chip independence

British in-orbit manufacturing venture Space Forge has appointed technology veteran Atul Kumar to set up a semiconductor business in the United States, aiming to bolster domestic chip production as efforts to reduce reliance on foreign suppliers gather pace.

The post Space Forge sees LEO as key to strengthening US chip independence appeared first on SpaceNews.

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Spirit Electronics Expands U.S. Semiconductor Capacity with Acquisition of SMART Microsystems

PHOENIX, Ariz. (April 10, 2025) – As part of its strategic commitment to strengthening domestic semiconductor manufacturing, Spirit Electronics has acquired SMART Microsystems, located at Lorain County Community College (LCCC) […]

The post Spirit Electronics Expands U.S. Semiconductor Capacity with Acquisition of SMART Microsystems appeared first on SpaceNews.

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