Category: 7. Science

It’s time to change crews on the International Space Station. On Friday, you can tune in to NASA’s live coverage of the return of Crew-10 on NASA+, Amazon Prime, and more streaming services. Events begin with the hatch closure and undocking on Friday, and the crew return on the following day. 

The return was delayed a day due to high winds at the splashdown sites off the coast of California. Weather conditions will be continually monitored and the specific splashdown location will be determined closer to the time of the Crew-10 spacecraft undocking.

Crew-10 has been at the International Space Station for five months, and is set to return a week after the arrival of the Crew-11 team on the 2nd of August. The returning crew consists of NASA astronauts Anne McClain and Nichile Ayers, along with JAXA astronaut Takuya Onishi and Roscosmos cosmonaut, Kirill Peskov. 

Here’s the schedule for live coverage, though it’s subject to change.

Friday, Aug. 8

3:45 p.m. – Hatch closure coverage begins on NASA+ and Amazon Prime.

4:20 p.m. – Hatch closing

5:45 p.m. – Undocking coverage begins on NASA+ and Amazon Prime.

6:05 p.m. – Undocking

After the day one coverage concludes, audio-only discussions will become available, including conversations from Crew-10 and the space station, as the SpaceX Dragon makes its journey back. 

Crew-11 consists of US astronauts Zena Cardman, Mike Fincke and Kimiya Yui, along with Roscosmos cosmonaut Oleg Platonov. They arrived at the ISS Aug. 2 and will stay for about six months.

Saturday, Aug. 9

10:15 a.m. – Return coverage begins on NASA+ and Amazon Prime.

10:39 a.m. – Deorbit burn

11:33 a.m. – Splashdown

1 p.m. – Return to Earth media teleconference will stream live on the agency’s YouTube channel, with the following participants:

• Steve Stich, manager, NASA’s Commercial Crew Program
• Dina Contella, deputy manager, NASA’s International Space Station Program
• Sarah Walker, director, Dragon Mission Management, SpaceX
• Kazuyoshi Kawasaki, associate director general, Space Exploration Center/Space Exploration Innovation Hub Center, JAXA 

Researchers have reinvented the classic “gene gun,” unveiling a breakthrough that could revolutionize how we grow food, reported Phys.org. This newly engineered device dramatically boosts the efficiency of genetic modification in crops, making it faster and easier to develop plants that can thrive amid climate challenges and support global food security.

Since 1988, scientists have relied on the gene gun to deliver DNA into plants by firing microscopic particles coated with genetic material directly into plant cells. While groundbreaking, the technique has long struggled with inefficiencies, inconsistent results, and damage caused by the high-speed particles. “We didn’t even know we had a problem,” said Kan Wang, an agronomist from Iowa State University. But that all changed when materials scientist Shan Jiang took a fresh look.

Jiang, whose postdoctoral work at Massachusetts Institute of Technology focused on delivering genetic therapies for human health, applied his expertise to plant science, a field often overlooked by engineers. He saw an opportunity to improve this decades-old technology by refining its internal mechanics.

“Very few materials scientists were working on plant cell delivery. Agriculture is always overlooked — people want to cure cancer,” he said.

After years of trial and error, the breakthrough came from a surprising place: computational fluid dynamics. The team discovered that a bottleneck inside the gene gun’s barrel was disrupting the flow of particles, leading to loss, uneven distribution, and slower speeds. By designing a new internal component, the “Flow Guiding Barrel,” and testing 3D-printed prototypes, they boosted performance by a staggering margin.

“It improved performance by 50%, then two, three, five, 10, 20 times,” Jiang said. “I was very shocked, to be honest with you.”

This upgrade means nearly 100% of particles now reach their target cells, compared to just 21% with the conventional design. Plant scientists saw efficiency improvements up to 22-fold in onions, 17-fold in maize seedlings, and doubled results using CRISPR genome editing in wheat.

Wang noted, “We’re able to work far more efficiently.” Yiping Qi, a University of Maryland plant scientist on the project, added that this innovation could simplify genome editing in multiple staple crops beyond wheat, such as barley and sorghum.

Beyond speeding up research, these advances could translate into more resilient crops that withstand more extreme heat and weather as well as pests, improve nutritional content, and reduce the environmental footprint of farming.

The Flow Guiding Barrel could save millions in research costs and shorten timeframes to bring enhanced crops to market, an urgent need as climate change threatens global food systems. “The benefits it can bring are invaluable,” Jiang said.

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If detecting exoplanets was easy, then we should have a complete understanding of the planetary system around our nearest stellar neighbour, Alpha Centauri. But we don’t, because it’s not easy. Alpha Centauri is a triple star system about 4.25 light-years away. The primary star is called Alpha Centauri A, a Sun-like star, and it’s in a binary relationship with Alpha Centauri B, another Sun-like star. The third star is a red dwarf named Proxima Centauri, and it’s the closest one to us.

Astronomers know of three confirmed exoplanets around Proxima Centauri, and there have been hints of other planets in the system orbiting the other stars. Confirming any of these planets has proven difficult. Now the JWST has found additional evidence of a gas giant orbiting Alpha Centauri A.

Two companion papers present the discovery. One is “Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of Alpha Cen A.
I. Observations, Orbital and Physical Properties, and Exozodi Upper Limits.” The co-lead authors are Charles Beichman from NASA’s Exoplanet Science Institute and JPL, and Aniket Singh from the California Institute of Technology and JPL.

The second paper is “Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of Alpha Cen A. II. Binary Star Modeling, Planet and Exozodi Search, and Sensitivity Analysis.” It shares the same co-lead authors.

“If confirmed, the potential planet seen in the Webb image of Alpha Centauri A would mark a new milestone for exoplanet imaging efforts.” – Aniket Sanghi, California Institute of Technology/JPL.

The planet is referred to as S1. It’s existence is difficult to conclusively prove because of noise from the three stars, zodiacal dust, and background sources. The astronomers used the JWST’s Mid-Infrared Instrument (MIRI) and its coronagraphic mask to detect it, and the detection took two years and required help from other telescopes.

“With this system being so close to us, any exoplanets found would offer our best opportunity to collect data on planetary systems other than our own. Yet, these are incredibly challenging observations to make, even with the world’s most powerful space telescope, because these stars are so bright, close, and move across the sky quickly,” said co-first author Beichman. “Webb was designed and optimized to find the most distant galaxies in the universe. The operations team at the Space Telescope Science Institute had to come up with a custom observing sequence just for this target, and their extra effort paid off spectacularly.”

Three views of Alpha Centauri from three different telescopes. The left image is from the ground based Digital Sky Survey and shows the triple star system as a single point of light. The middle image is from the Hubble Space Telescope and shows A Cent A and A Cent B separately. The third image is from the JWST’s MIRI and its coronagraph, and shows A Cent A and the candidate planet. Image Credit: NASA, ESA, CSA, STScI, DSS, A. Sanghi (Caltech), C. Beichman (JPL), D. Mawet (Caltech), J. DePasquale (STScI). LICENCE: CC BY 4.0 INT or ESA Standard Licence

Searching for a planet around Alpha Centauri A is extremely complicated. Astronomers have to account for the star’s proper motion and the light from the star’s binary companion. They needed to use reference stars to calibrate their observations, but that’s complicated by the fact that they have to be bright enough compared to Alpha Centauri A. The reference stars also have to have similar photospheric properties to the coronagraphic filter being used, in this case, F1550C. Due to filtering and stellar brightness, the astronomers also had to use blind offset stars to track Alpha Centauri A. They used Epsilon Muscae (e Mus) as a blind offset star, and also used a guide star to acquire it. On top of that, they had to use computer simulations of its orbit. That’s a dictionary definition of complicated.

These images illustrate some of the difficulty in searching for exoplanets around Alpha Centauri A. The image on the left shows Alpha Centauri AB, the binary star, and Gaia stars in green boxes. Red boxes are MIRI point source detections. The stars labelled G0 and G5 were used for target acquisition. The right panel shows the bind offset star Epsilon Muscae, and a guide star labelled G9 used to acquire Eps Muscae. Image Credit: Beichman, Sanghi, et al. 2025. ApJL

If the planet can be confirmed, it will be a noteworthy discovery. It would be the closest habitable zone planet orbiting a Sun-like star. Since it’s gas giant, it is not habitable, but its proximity still makes it a scientifically valuable observational target.

The first JWST observations are from August 2024. These were tricky, because although MIRI has a coronagraph, there are multiple stars to contend with. The coronagraph blocked out the light from Alpha Centauri A, but bright light from its companion Alpha Centauri B complicated the observations. The researchers were eventually able to block out Alpha Centauri B’s light. That revealed the presence of an object 10,000 times dimmer than Alpha Centauri A. It’s separated from the star by about 2 au.

With this initial detection of an exoplanet candidate, excitement built. But these observations alone weren’t enough to confirm it. The team conducted more observations with the JWST’s Director’s Discretionary Time in February and April of 2025, and those proved inconclusive.

This is JWST’s view of the Alpha Centauri AB system. The candidate planet is seen in the images from August 2024, but not in subsequent images. Image Credit: Beichman, Sanghi, et al. 2025. ApJL

JWST observing time isn’t handed out like candy, and requests for more were not in the cards. Instead, the researchers worked with the observational data they’d already acquired and turned to computer models to take the next step.

“We are faced with the case of a disappearing planet! To investigate this mystery, we used computer models to simulate millions of potential orbits, incorporating the knowledge gained when we saw the planet, as well as when we did not,” said PhD student Aniket Sanghi of the California Institute of Technology in Pasadena, California. Sanghi is also a co-first author on the two papers covering the team’s research.

Here’s where another potential exoplanet enters the picture. In 2021, astronomers working with the VLT detected a candidate planet around Alpha Centauri A referred to as C1. When considering potential orbits for S1, the team also had to consider C1.

“With only a single JWST/MIRI sighting (and non-detections at two other epochs), it is challenging to uniquely constrain the orbit of S1,” the authors explain. To make progress, they decided to consider C1 as an earlier detection of the newly-detected S1, which they refer to as the S1 + C1 candidate.

This figure shows 100 randomly selected stable planetary orbits fitting the S1+C1 astrometry (marked as green points) and consistent with the February and April 2025 non-detections, for each orbital family. Image Credit: Beichman, Sanghi, et al. 2025. ApJL

“We find that 52% of the stable orbits that fit the S1 + C1 astrometry are also consistent with non-detections in both February and April 2025,” the authors write. “There is, thus, an a priori significant chance that, if real, the planet candidate could have been missed in both follow-up observation epochs.”

“We found that in half of the possible orbits simulated, the planet moved too close to the star and wouldn’t have been visible to Webb in both February and April 2025,” said Sanghi.

In the end, the researchers think they’ve discovered a Saturn-mass gas giant orbiting Alpha Centauri A. They say it follows an eccentric orbit that moves within 1 to 2 au of the star. The planet is a bit brighter than expected for its type, so they say zodiacal dust could be contributing. The planet could also be rotating rapidly, if being viewed from the pole, could show more surface area. Or it could have rings like Saturn does.

When the JWST was being designed and then launched, scientists knew how powerful it would be. The telescope excels at looking back in time at extremely distant galaxies and supermassive black holes, but that same power can be used on our closest stellar neighbour. Directly imaging a nearby exoplanet is a stunning achievement. According to the researchers, these are some of the most complex and demanding observations performed with the space telescope.

“These are some of the most demanding observations we’ve done so far with MIRI’s coronagraph,” said Pierre-Olivier Lagage, of CEA, France, who is a co-author on the papers and was the French lead for the development of MIRI. “When we were developing the instrument we were eager to see what we might find around Alpha Centauri, and I’m looking forward to what it will reveal to us next!”

“If confirmed, the potential planet seen in the Webb image of Alpha Centauri A would mark a new milestone for exoplanet imaging efforts,” Sanghi says. “Of all the directly imaged planets, this would be the closest to its star seen so far. It’s also the most similar in temperature and age to the giant planets in our solar system, and nearest to our home, Earth,” he says. “Its very existence in a system of two closely separated stars would challenge our understanding of how planets form, survive, and evolve in chaotic environments.”

Scientists have a fairly good idea of what Mars’ surface looks like. But exactly what that surface is made up of is more of a mystery. 

Now, scientists believe they have discovered an entirely new mineral on Mars from an unusual layer of iron sulfate with a distinct spectral signature. In a Nature Communications paper published on August 5, astrobiologists led by Janice Bishop at the SETI Institute describe the discovery of an unusual ferric hydroxysulfate compound around Valles Marineris, a vast chasm that sits along Mars’ equator. It’s an area that researchers suspect once flowed with water, and the new mineral’s discovery could offer tantalizing clues as to how and what natural forces sculpted the planet’s surface—and whether life once thrived on Mars. 

Sulfur, an element common to both Mars and Earth, often combines with other elements to form minerals in the form of sulfates. These minerals dissolve easily in water, but unlike Earth, Mars has persistently dry weather, meaning that sulfates may have remained on the surface since the planet lost its water. Studying these minerals, therefore, would uncover important information about Mars’ early history.

The researchers investigated sulfate-rich areas near Valles Marineris, paying special attention to regions that “included mysterious spectral bands seen from orbital data, as well as layered sulfates and intriguing geology,” explained Bishop in a statement. 

In one area, they found layered deposits of polyhydrated sulfates, with monohydrated and ferric hydroxysulfates underneath.

They tried to recreate these in the lab, finding that the ferric hydroxysulfate seen on Mars could only have formed in the presence of oxygen and that the reaction needed to produce the compound produces water. Further, this could only have happened at high temperatures, the researchers said, suggesting the sulfates formed from volcanic activity. What’s more, its structure and thermal properties suggest it is a totally new mineral.

“The material formed in these lab experiments is likely a new mineral due to its unique crystal structure and thermal stability,” Bishop said. “However, scientists must also find it on Earth to officially recognize it as a new mineral.”

A dull stretch of silty seafloor off Southern California hides a surprise that would fit on a pencil eraser. Here, three new sea spiders in the genus Sericosura have learned to live on the greenhouse gas methane, thanks to a cloak of bacteria that carpets their limbs.

The work comes from marine biologist Shana Goffredi at Occidental College, whose team used remotely operated vehicles to collect the translucent arachnid cousins nearly 3,350 feet down. They then tracked carbon from labeled methane directly into the spiders’ tissues.

Deep, dark habitat

Light never reaches the Pacific methane seep, a spot where gas seeps through cracked sediment instead of burning in kitchen stoves.

In such places, free-living microbes turn methane and oxygen into simple sugars, laying the energy groundwork for whole communities.

Most animals here hunt or filter food, but the palm-sized Sericosura do neither. Their proboscis lacks the piercing teeth used by other sea spiders to drain jellyfish, so the team looked for a different menu.

Sea spiders and a methane buffet

Under an electron microscope, each spider leg resembles rough sandstone, dotted with thousands of tiny “volcano” pits.

Every pit holds a tuft of methanotroph cells encased in sticky gel, stacked like poker chips and spaced about five-hundredths of an inch apart.

The pattern is no accident. NanoSIMS imaging showed the bacteria gulping heavy-carbon methane and multiplying rapidly.

They then disappeared in patches, leaving clear tooth marks that match the spider’s flexible mouthparts.

“Just like you would eat eggs for breakfast, the sea spider grazes the surface of its body, and it munches all those bacteria for nutrition,” said Goffredi.

Methane fuels spider meals

Methanotrophs oxidize methane, releasing both carbon dioxide and a dash of methanol.

Secondary bacteria on the spider, mainly Methylophagaceae, slurp the methanol, forming a two-tier farm much like the mixed crops found on deep-sea tubeworms and yeti crabs.

Labeling experiments ran for five days in chilled seawater. By then, carbon from the methane had already reached the spider’s digestive diverticula.

This proved that the animal swallows its tenants rather than absorbing leftovers through its skin.

Spider eggs carry bacteria

Male Sericosura brood strings of eggs around their knees like charm bracelets. Goffredi’s team noticed the same bacterial mix coating the egg sacs, suggesting parents seed their young with food before the larvae ever crawl.

Vertical transfer of symbionts is common in deep-sea mussels and hydrothermal vent crabs.

Finding the pattern in a pycnogonid hints that inheritance of microbiomes may be older and more widespread than researchers thought.

“Even if 80 percent of the population are eaten, it’s worth it for the 20 percent to keep surviving and reproducing,” said Max Planck symbiosis expert Nicole Dubilier, who reviewed the data but was not involved in the fieldwork.

Methane spiders reshape theory

The fact that sea spiders graze their own bodies for fuel points to an overlooked path in the global carbon cycle.

Until now, most methane-fed ecosystems were thought to rely on internal symbionts or sediment-dwelling microbes, not animals farming bacteria on their skin.

Because methane seeps span thousands of miles of coastline, even small-bodied grazers like Sericosura could collectively process meaningful amounts of gas before it escapes to the surface.

That adds a new twist to how scientists model methane flux in oceanic systems and may influence how future conservation zones are drawn.

Small farmers, global effects

Each bacterial layer that ends up inside a spider is a layer that never reaches the atmosphere as methane.

Deep-sea sponges at asphalt seeps can already lock away up to 22 percent of local emissions through similar partnerships.

Hundreds of seeps dot the Pacific margin, and many companies have slated them for mineral surveys.

Because the newly described spiders sit in pockets no bigger than a two-car garage, any disturbance risks wiping out entire populations and their methane filters overnight.

Goffredi hopes the unique chemical signature in the spiders’ bodies will help crews spot hidden methane seeps before drilling starts.

This method has already helped identify other deep-sea hotspots, like sponge fields and tubeworm colonies.

Methane may spell trouble in the sky, yet in the deep it fuels intricate symbiosis that strings bacteria, spiders, and climate together.

Tiny as they are, the Sericosura colonies remind us that saving obscure life forms can pay off far above their dark, pressurized homes.

The study is published in Proceedings of the National Academy of Sciences.

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Ever since William Harvey outlined the circulation of the blood, textbooks have assigned distinct roles to blood’s cellular cast.

Platelets served as the tiny workhorses that pulled clotting protein threads tight, white cells patrolled for infection, and red blood cells (RBCs) mostly hauled oxygen while passively filling space inside a forming clot.

A collaborative study from the University of Pennsylvania now overturns that familiar picture. Using a blend of biochemical tricks, high-resolution imaging, and mathematical modeling, the investigators show that red blood cells actively generate the forces that make a clot shrink and toughen once it has sealed a wound.

“This discovery reshapes how we understand one of the body’s most vital processes,” said senior author Rustem Litvinov from the Perelman School of Medicine (PSOM).

The project drew on expertise that spans hematology, cell biology, and soft-matter mechanics, illustrating how interdisciplinary science can upend long-held assumptions.

Clots shrink without platelets

John Weisel, a professor of cell and developmental biology at PSOM, has spent decades probing fibrin – the insoluble, rope-like protein network that glues a clot together.

In previous studies, he and Litvinov had dissected how platelets tug on fibrin fibers. So when they decided to revisit that system without platelets, they expected an inert mass.

Professor Weisel said the team did not expect anything to happen. “Instead, the clots shrank by more than 20 percent.”

To rule out platelet activity, the team used blood treated to block the platelets’ ability to contract. Once again, the clots pulled inward. At that point, the researchers confronted the unanticipated culprit.

“Red blood cells were thought to be passive bystanders,” Weisel said. Far from passive, the cells appeared to be doing mechanical work.

“That’s when we realized red blood cells must be doing more than just taking up space,” Litvinov explained.

Red cells act like gels

How could flexible discs with no contractile proteins of their own produce force? The Penn biologists enlisted Prashant Purohit, a professor of mechanical engineering and applied mechanics who specializes in the behavior of gels and other squishy materials.

“Red blood cells have been studied since the 17th century,” noted Purohit. “The surprising fact is that we’re still finding out new things about them in the 21st century.”

Purohit constructed a mathematical model grounded in colloid physics. As a clot forms, fibrin polymerizes into a porous mesh. This mesh traps RBCs along with plasma proteins such as albumin and fibrinogen.

When the mesh compacts, large protein molecules are squeezed out of the tight spaces between adjacent red cells faster than they can leave the surrounding fluid. That imbalance, known as an osmotic depletion force, produces an external pressure that pushes the trapped cells into even closer contact.

Packed blood cells shrink the clot

“Essentially, the proteins in the surrounding fluid create an imbalance in pressure that pushes red blood cells together,” Purohit said.

The packed cells transmit the pressure back to the fibrin scaffold, making the entire clot shrink and stiffen.

“This attractive force causes them to pack more tightly, helping the clot contract even without platelets,” he added.

The model also permitted the team to quantify a second, previously proposed mechanism: molecular bridging. In this process, complementary molecules on neighboring RBC membranes bind together.

Clot behavior matches math

Study first author Alina Peshkova, now a postdoctoral researcher in pharmacology at Penn, designed a series of clotting assays to test the model head-on.

When she blocked the membrane molecules required for bridging, clots still contracted robustly. When she manipulated the chemical environment to eliminate the osmotic pressure gradient, contraction was largely abolished.

“We experimentally confirmed what the model predicted,” Peshkova said. “It’s an example of theory and practice coming together to support each other.”

Findings may impact stroke care

Most acute clotting problems in medicine trace back to an imbalance between clot formation and dissolution.

If RBC-driven contraction proves to be a major determinant of clot strength in vivo, it could help explain why patients with anemia or sickle cell disease sometimes experience unusual clotting complications.

Conversely, individuals with very low platelet counts (thrombocytopenia) might still achieve adequate clot retraction if their red cells provide compensatory force.

A better grasp of clot mechanics is also relevant to thromboembolism. A clot that retracts too vigorously can become so dense that fragments break off and travel downstream, lodging in the lungs, coronary arteries, or brain.

Understanding how osmotic forces affect clot architecture may therefore inform strategies to prevent strokes or pulmonary emboli.

“Ultimately, our model is going to be helpful in understanding, preventing, and treating diseases related to clotting inside the bloodstream,” Purohit said.

Physical forces reshape biology

The Penn study showcases the power of looking at a biological question through a physical lens. Osmotic depletion had long been recognized in industrial colloids – pigment particles in paint, milk proteins in dairy science – but had received little attention in hemostasis research.

By merging classic hematology with contemporary soft-matter theory, the investigators revealed that an abundant, well-studied cell type still harbors surprises that matter for human health.

“This attractive force causes them to pack more tightly, helping the clot contract even without platelets,” Purohit emphasized.

The remark captures the study’s dual message: mechanical laws operate inside living tissues, and basic science can still revise what clinicians think they already know.

With platelet-free contraction now firmly established, the field can move on to explore how genetic diseases, pharmaceuticals, or blood storage conditions influence this newly recognized RBC function.

Researchers can also investigate whether tweaking it might tip the balance between life-saving hemostasis and life-threatening thrombosis.

The study is published in the journal Blood Advances.

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Physicists can map its gravity, tally its cosmic abundance, and observe its fingerprints in the microwave glow of the Big Bang. Yet no one has ever detected a single particle of dark matter in the laboratory.

That enduring mystery drives much of today’s theoretical physics, and few researchers are pushing the boundaries more vigorously than Professor Stefano Profumo at the University of California, Santa Cruz.

In two recent papers, Profumo offers separate – yet thematically linked – visions of how dark matter might have emerged naturally from the earliest moments of cosmic history rather than through new interactions with ordinary matter.

Dark matter from a “mirror world”

The first study, published in the journal Physical Review D, asks whether dark matter could consist of ultra-compact black-hole – like objects forged in a hidden sector that mirrors the familiar world of quarks and gluons.

Drawing inspiration from quantum chromodynamics, Profumo and collaborators imagine a “dark QCD” with its own quarks, gluons, and strong nuclear force.

In the scorching seconds after the Big Bang, dark quarks could have bound into heavy composite states – dark baryons.

These baryons may have later collapsed under their own gravity, leaving behind relics only a few times heavier than the Planck mass.

These remnants interact only via gravity, slipping past detectors while explaining the universe’s missing 80 percent of matter.

This scenario nods to a rich Santa Cruz pedigree. Former UCSC professor Michael Dine helped pioneer the QCD axion hypothesis, another leading dark-matter idea.

Research Professor Abe Seiden also contributed to experiments probing the internal structure of hadrons.

Profumo’s work revives that tradition, extending well-tested gauge theories into a shadow realm. It reveals a new way composite physics might answer the dark-matter riddle without contradicting existing data.

Dark matter in an expanding universe

Profumo’s other paper, published in the same journal, pivots from hidden sectors to the fabric of spacetime itself.

He explores the possibility that an episode of accelerated expansion after cosmic inflation could have generated dark matter particles.

This expansion was slower than primordial inflation but faster than what ordinary matter or radiation would allow, resembling how a black hole’s event horizon is predicted to radiate.

Using quantum field theory in curved spacetime, he calculated that a brief phase of quasi-de Sitter expansion could “heat” the universe’s horizon.

This process would spontaneously produce an ample abundance of stable, non-interacting particles over a broad mass range.

No additional forces or couplings are required; gravity alone does the job. Both mechanisms avoid needing detectable interactions, which increasingly sensitive underground experiments have repeatedly failed to observe.

“Both mechanisms are highly speculative, but they offer self-contained and calculable scenarios that don’t rely on conventional particle dark matter models, which are increasingly under pressure from null experimental results,” explained Profumo.

Architecture of the universe

Profumo literally wrote the textbook on this pursuit. His 2017 volume An Introduction to Particle Dark Matter remains a touchstone for students and researchers alike.

The new studies continue UCSC’s long-standing approach of fusing particle theory, cosmology, and astrophysics. This approach helped establish the Lambda-Cold Dark Matter model currently favored by observational data.

The campus’s Institute for Particle Physics and its theorists have repeatedly shown how fresh ideas about the micro-world can illuminate the large-scale architecture of the universe.

Professor Profumo emphasized that the proposals rest on physics already in hand, not speculative new forces.

The hidden-sector picture leans on well-studied SU(N) gauge theories. The horizon-production mechanism relies on the same mathematics that underpins Hawking radiation.

Hints in gravitational waves

Neither idea will be easy to confirm. Dark-sector black holes would evade direct detection and might reveal themselves only through subtle gravitational-wave signatures or small anomalies in the cosmic microwave background.

Horizon-generated particles would likewise be invisible except through their influence on the growth of cosmic structure or precision measurements of Big Bang nucleosynthesis.

Yet both frameworks make quantitative predictions that could guide future observations. These range from the Laser Interferometer Space Antenna’s (LISA) hunt for primordial black hole mergers to next-generation surveys mapping dark matter distributions on megaparsec scales.

Meanwhile, Professor Profumo and his colleagues are refining the math. They are exploring, for instance, how different dark-QCD parameters affect the mass spectrum of possible mini-black-hole remnants.

The researchers are also examining how varying the duration of post-inflationary acceleration changes the predicted relic abundance. Each tweak produces patterns that upcoming data sets may support or rule out.

Mirror worlds and dark matter hunting

The null results piling up at direct-detection experiments have encouraged theorists to broaden their horizons, both figuratively and literally.

By rooting his models in established quantum field theory and gravitation, Profumo offers a pair of audacious yet disciplined road maps. These maps outline where dark matter might have come from – and how researchers could someday prove it.

Whether the answer lies in a shadowy confining force or in particles born at the edge of the universe’s own horizon, the work demonstrates how much fertile ground remains between the known and the unknown.

In the search for the cosmos’s invisible matter, these studies remind us that sometimes the boldest steps forward come from looking back. They point to the Big Bang’s first moments, when galaxies, stars, and hidden particles first began to take shape.

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The obtained GaN nanocrystals have a hexagonal wurtzite structure, which was confirmed by XRD measurement, shown in (Fig. 1).

According to the pattern (ICSD #34476), the obtained GaN nanocrystals have a pure structure with the broad reflections indicating nanosize. The average grain size was calculated by Rietveld analysis to be 12 nm. The absorption spectrum of GaN nanocrystalline powder is shown in (Fig. 2). By using the Kubelka-Munk function²⁷ the energy band gap was determined to be 3.17 eV. Due to the nano-size of the particles, there are various defects in the structure, such as Ga and N vacancies, surface defects, or grain boundary defects. Therefore, the absorption edge shifts towards lower energies²⁸ so the experimental value of the energy gap is smaller than the theoretical one of 3.4 eV²⁹.

The wide band emission of GaN nanopowder in a range 405–650 nm with the maximum at 439 nm is shown in (Fig. 2c). Their deconvolution was performed to better understand the nature of the emission bands, resulting in five components with local maxima at 2.18 eV, 2.58 eV, 2.68 eV, 2.84 eV and 3 eV. The more intense bands 2.84 eV and 2.68 eV are most likely associated with V_Ga vacancies, and the remaining bands with V_N vacancies²⁸. The peaks at 3 eV, 2.84 eV are closest to the energy gap value, and may also be related to excitonic recombination³⁰. The broad peak at 2.58 eV and the residual peak at 2.68 eV possibly relate to the presence of luminescent centers causing edge shifts for gallium and nitrogen vacancies³¹. The obtained material is also characterized by an undesirable yellow component of luminescence, which is caused by structural defects, indicating the imperfect structure of the obtained material^2,32.

The research focuses on broadband white light emission (LIWE) characteristics and the accompanying photocurrent phenomenon. First, the studies show that a curve like a hysteresis loop can be observed by measuring the laser power density in the direction forward and backward. So far, two articles have been published attempting to explain the occurrence of hysteresis. These articles focus on carbon materials, diamond²⁴and graphene³³.

Due to its wide band gap, high thermal conductivity, and chemical stability, GaN is a suitable material for LIWE and photoconductivity investigation. The laser induced white emission spectra measured for GaN nanoceramics for both, visible and near-infrared regions are shown in Fig. 3a, b, respectively. It was characterized by broad bands whose intensity increases exponentially with excitation laser power density and leads to a blueshift of the bands. An increase in LIWE emission intensity starts after crossing the characteristic excitation threshold. The band extends from 400 to 2500 nm with a maximum of 1695 nm. For both regions, the emission threshold is estimated to be slightly above 1 kW/cm². The emission intensity measurements were obtained using two detectors, which is why the emission intensity can be different, and the gap between the visible and near infrared regions results from the use of optical filters and the cutting of the excitation laser beam. Nevertheless, based on these spectra and the N parameter, which in both cases takes similar values, it can be suggested that this is a single broad band. It has also been reported that the two bands measured separately are actually one band³⁴. Furthermore, experiments were performed for both regions, initiating hysteresis shape curve by measuring forward with increasing laser power density and then backward with decreasing laser power density. The results are shown in (Fig. 3c,d). In both cases, the characteristic properties of this phenomenon are preserved. The resulting loops are characterized by a threshold value followed by increased emission intensity. Moreover, saturation was demonstrated at high laser power densities. Furthermore, in the case of backward measurements, the N parameter for both ranges has higher values. Additionally, the emission threshold shifts towards higher power densities and saturation does not occur due to the lack of hysteresis. The SI (Figure S1) shows the CIE chromaticity diagram, demonstrating the objective color quality for both anti-Stokes and Stokes emissions. LIWE is characterized by a warm yellow color. Depending on the laser power density, the x and y coefficients locations differ, and as the laser power density increases, it is noticed that the emission color temperature changes towards white.

It was found that the investigated process is assisted by photoconductivity. Therefore, changes in sample resistance were measured depending on the laser power in cycles where the laser was turned on and off every 30 s. The changes were recorded at various voltage biases, as shown in (Fig. 4a). No changes in material resistance were observed at low laser powers, while at higher powers, a decrease in resistance was already observed. This is related to the threshold nature of both white emission and photocurrent. The dependence of resistance on the laser power density was plotted, and the excitation threshold was observed (Fig. 4b). Moreover, the applied voltage affects the initial resistance value. For 5 V, the resistance was the lowest, whereas the highest resistance was observed at 150 V. It should be noted that the resistance was dependent on the applied voltage up to 50 V, and then the saturation was observed. The initial value of resistance is similar for 50 V, 150 V, and 250 V. It can be observed that the photocurrent increases by two orders of magnitude with increasing excitation laser power. The excitation threshold was determined to be about 3 kW/cm² (see Table S1 in SI).

White emission and photoconductivity were simultaneously performed in laser power density cycles (Fig. 5). The experiments were performed twice in closed (forward and backward) cycles. The differences can be noticed depending on whether the initial laser power density was low or high. For the first one, the hysteresis loop was observed for both LIWE and LIPC processes. However, hysteresis did not occur during measurements from a high initial laser power density.

The LIWE mechanism has been explained many times, including as blackbody radiation^35,36 thermal avalanche^14,19,37 or intervalence charge transfer^38,39,40,41. The characteristics of LIWE are mostly the same, so the mechanism should also be very similar. In this work, to explain the processes taking place, a proposed scheme (Fig. 6.) was used, in which the phenomenon is divided into stages: process before reaching the threshold value, multiphoton ionization and radiative recombination during irradiation after reaching the threshold value and possible occurrence of saturation with a high density NIR laser power.

At low laser power densities, no light is observed until the threshold is exceeded. This is due to the number of photons delivered to the sample surface. GaN nanoceramics is excited with an NIR laser with an energy of 1.27 eV, while the experimental value of the energy gap is 3.17 eV. With the laser power density increase, the probability of photons hitting the same electron increases, ejecting it of the valence band. Then, the multiphoton avalanche process leads to multiphoton ionization on the surface of the tested material. The phenomenon is nonlinear and with the increase of the laser power density, the intensity of emission increases. The dependence of LIWE intensity I(P) on the excitation laser power is usually characterized by the power law formula:

where I(P) is the emission intensity, P is the excitation laser power, and N is related to the number of photons. This equation is used to describe multiphoton absorption transitions. Based on research in our group, where the dependence of power was plotted in different excited spot size it was found that the parameter N cannot be unambiguously treated as the number of absorbed photons. Based on this analysis, one should be more careful in connecting the nonlinearity of the process defined by the parameter N with the actual number of photons participating in the reaction^31,42. The process of multiphoton ionization (MPI) in irradiated spot at the surface of GaN nanoceramics leads to the broadband white emission (LIWE) assisted by an ejection of hot electrons e⁻ and may be described as:

where MA(Nħω) expresses the multiphoton absorption responsible for the multiphoton ionization of the GaN, GaN + is ionized GaN (cathode), LIWE represents laser induced white emission, and NR characterizes the nonradiative quenching and phonon emission processes contributing to the enhancement of thermally active processes. At higher laser power densities, more photons are transmitted to the sample surface, causing electrons to be emitted from the valence band to the conduction band. In addition, a radiative recombination process occurs. An electron from the conduction band recombines with a hole from the valence band, emitting a photon. This process is repeated until all possible emission centres are used. Saturation often occurs. The LIWE still occurs, but its intensity often remains unchanged or decreases. This is probably related to the confinement of some electrons, thus maintaining LIWE. The lack of new emission centres causes a lack of increase in emission intensity.

As explained above, during near-infrared laser irradiation of a sample in a dynamic vacuum, many processes occur, often overlapping. The hysteresis loop is probably formed not only due to photophysical processes but also because of morphological changes. Due to the fact that the measurements were performed depending on the density of the excitation laser beam on nanometric material, changes in the morphology of the sample may have occurred. When the measurement was performed from the lowest laser power, there could have been gradual ionization in GaN, an increase in temperature in the irradiated spot, and changes in morphology after obtaining a high power density. The following changes resulted in a different course when the laser power density decreased. This suggests an irreversible response of the material to the excitation condition. In turn, in the opposite case, the material was first irradiated with high laser power density, probably causing simultaneous ionization and another photophysical process explained in the proposed mechanism, changes in morphology, and high temperature at the beginning. Changing the density to a lower and then to a higher density does not cause changes in the emission intensity, which can confirm the conclusions drawn. Stręk et al.²⁴ reported the hysteresis loop behavior for LIWE on diamond material. They explain this as an irreversible process caused by multiphoton ionization. The degree of ionization is related to the irradiation of the sample and the number of ionized atoms. This phenomenon can be used as an effective optical memory. In our case, the confirmation of irreversible process can be repeated measurement of the loop under the same conditions and at the same point, and likewise, the backward cycle, because under high density, the hysteresis loop does not occur. Additionally, based on an article from Zheng et al.23, where an experiment was performed in which two curves were recorded, one for the excitation laser turned on and the other for the excitation laser turned off, a change in the emission intensity was observed, which suggested that the process is not only thermal.

The broadband white light emission phenomenon began to be associated with the photocurrent that appears during sample irradiation. To characterize LIPC, the same formula as in the case of LIWE can be used because both phenomena are nonlinear and exhibit a threshold character. The dependence of photoresistance R on laser power density can be expressed by:

where N_pc is related to the order of multiphoton ionization. The observed drop in resistance after reaching the threshold value is related to photoionization. After the material absorbs infrared photons, charge carriers are created. The higher laser density, the higher number of photons leading to stronger electron-hole recombination and, consequently, higher conductivity.

When discussing the LIWE and photocurrent phenomena, other factors are also considered, with one of the most important being the influence of temperature on the phenomena under study. LIWE was tested in many different luminescent materials, and it can be concluded that the shape of the emission does not depend on the host lattice. However, this phenomenon can be linked to the thermally assisted ionization process and strong optical nonlinearity. The differences resulting from the investigation are mainly associated with a change in the N parameter, depending on the material being tested. Interpretations of this behaviour should be considered. Since the experiments were performed on ceramics, the grains are as close to each other as possible, which reduces the energy localization in the laser spot and increases energy losses due to, for example, heat conduction and changes in the non-linearity of the process²³. The temperature of emission at different power densities was calculated using the Planck equation (see Table S2 in Supporting Information)

where h is Planck’s constant, c is the velocity of light, λ is the wavelength (nm), and k_B is Boltzmann’s constant. The spectrum is dependent on the temperature of the sample. Based on this calculation the temperature was fitting with a good comparison both in relation to the theoretic temperature values associated with blackbody radiation and in relation to the fit of these values in the CIE chromaticity diagram. Despite the good fit of the temperature to Planck’s law, LIWE is mainly caused by the sample ionization process. As shown in articles on other materials, significant differences are observed between the temperature values ​​during LIWE. Using measurements with a thermal camera, the maximum temperature is read at about 1230 K²³. In the case of other articles, measurements of luminescence nanothermometry, where the emission intensity ratio ²H_11/2 ◊ ⁴I_15/2 to ⁴S_3/2 ◊ ⁴I_15/2 of Er³⁺ ion is used as a temperature probe, the observed maximum temperature takes values ​​of about 900 K³⁹. Then, it can be assumed that such differences can be observed in these studies as well, at least because the temperature values based on black body radiation are directly related to a very small point on the sample surface during emission, while the thermal camera shows values where the spot is wider. In connection with this, the temperature distribution is not clearly defined, and the small size of the spot in the laser focus does not allow for direct, accurate measurement without luminescence thermometry. Here one should be careful because, as described above, this method gives values ​​much lower than the blackbody fitting. The question still remains how to properly determine the temperature, such studies are required in the future.

CAPE CANAVERAL, Fla. — The Hubble Space Telescope has captured the best picture yet of a high-speed comet visiting our solar system from another star.

NASA and the European Space Agency released the latest photos Thursday.

Discovered last month by a telescope in Chile, the comet known as 3I-Atlas is only the third known interstellar object to pass our way and poses no threat to Earth.

Astronomers originally estimated the size of its icy core at several miles (tens of kilometers) across, but Hubble’s observations have narrowed it down to no more than 3.5 miles (5.6 kilometers). It could even be as small as 1,000 feet (320 meters), according to scientists.

The comet is hurtling our way at 130,000 mph (209,000 kph), but will veer closer to Mars than Earth, keeping a safe distance from both. It was 277 million miles (446 million kilometers) away when photographed by Hubble a couple weeks ago. The orbiting telescope revealed a teardrop-shaped plume of dust around the nucleus as well as traces of a dusty tail.

Dunn writes for the Associated Press. The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.