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Cosmic dawn fuel discovery unlocks early galaxy growth secrets

Astronomers have discovered a huge reservoir of cold molecular gas, the direct fuel for star formation, in REBELS-25, a massive, star-forming galaxy. The team, led from Leiden University, focused on REBELS-25, seen when the universe was only about 700 million years old, around 5% of its current age. The research is published in the journal Monthly Notices of the Royal Astronomical Society.

Astronomers use “redshift” to describe this distance, which measures how much the universe’s expansion has stretched a galaxy’s light to redder wavelengths. The higher the redshift, the farther back in time we look. REBELS-25 sits at redshift z = 7.3, deep in the Epoch of Reionization, a key era in which the first stars and galaxies transformed the dark, neutral universe into the universe we see around us today.

Galaxies grow by turning gas into stars, and cold molecular gas is the primary fuel. Until now, astronomers suspected early bright, massive galaxies had huge gas supplies, but no one had directly detected them at these distances.

New cavity control strategy improves performance of blue vertical-cavity surface-emitting lasers

GaN-based vertical-cavity surface-emitting lasers (VCSELs) are promising for displays, sensing and optical communication, but improving efficiency remains challenging. Researchers have now shown that “cavity tuning,” which controls resonance wavelength, strongly affects laser performance. By analyzing variations across a VCSEL wafer, the team identified optimal mirror loss conditions and extracted device parameters. Their approach achieved 26.4% wall plug efficiency, offering guidance for next-generation high-efficiency visible-light semiconductor lasers.

Gallium nitride (GaN)-based vertical-cavity surface-emitting lasers, or VCSELs, are attracting increasing attention as compact and energy-efficient light sources for future technologies. These semiconductor lasers are considered promising for applications such as next-generation displays, biometric sensing, environmental monitoring and short-range optical communication. However, improving their efficiency has remained a major challenge because laser performance depends strongly on precise optical design and cavity control.

Addressing this challenge, a research team led by Professor Tetsuya Takeuchi, Professor Satoshi Kamiyama and Professor Motoaki Iwaya from the Department of Materials Science and Engineering, Meijo University, Japan, along with Mr. Naoki Shibahara, first author and graduate student at the Graduate School of Science and Technology, Meijo University, Japan, investigated how “cavity tuning” influences the lasing characteristics of GaN-based VCSELs. While conventional studies mainly focused on gain tuning, also known as detuning, the researchers demonstrated that resonance wavelength alignment relative to the distributed Bragg reflector center wavelength critically affects laser operation.

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Water locked in 1-nanometer channels could enable safer energy storage

Can pure water store electrical energy? A research team led by Dr. Vasily Artemov within the Cluster of Excellence “BlueMat—Water-Driven Materials” at Hamburg University of Technology has now shown that it can. By confining water within nanometer-sized channels in clay minerals, the researchers created a supercapacitor capable of efficiently storing and transporting electrical charge.

What makes the finding unusual is that it uses pure water as its electrolyte—the medium that transports electrical charge. Today’s batteries and supercapacitors typically rely on added salts, acids, or other chemical electrolytes. In contrast, the new system works without such additives and is based solely on abundant, naturally occurring materials: water, clay, and carbon.

“Our goal is to develop safer and more sustainable energy-storage technologies based on abundant materials rather than complex chemical compounds,” says Artemov, lead author of the paper published in Nature Communications. “The device stores and releases energy efficiently, operates at a comparatively high voltage for a water-based system, and remains stable over tens of thousands of charging cycles.”

A low-tech solution to the 6G problem—metacrystal panels offer cheap way to guide wireless signals around corners

A passive 3D-printed panel could redirect wireless signals around corners without electronics or power. The metacrystal design can handle multiple incoming waves and different frequency bands, offering a lower-cost option for hard-to-reach indoor spaces.

Basements, tunnels, large buildings—a weak Wi-Fi or mobile signal in these hard-to-reach places is frustrating. The usual solution is to add more electronics like routers, repeaters and base stations. Yet, as we move towards a 6G mobile network, this kind of complex infrastructure can be unsustainable and prohibitively expensive. Higher-frequency channels of 6G communications aim to provide vastly more data bandwidth than the current 5G, but those channels are more easily blocked by walls, people and other obstacles.

To tackle this, researchers at Aalto University have developed a new solution in the form of metacrystals: passive, 3D-printed smart panels that can shape wireless signals without electronics, a power supply or active tuning. The paper, “Metacrystals: Inversely-designed 3D-printed intelligent panels for 6G communications” is published in Nature Communications.

“When a room is too dark, you can bring in more lamps—or use simple mirrors to guide the already available light. This is what these metacrystals do, but with radio waves,” explains doctoral researcher Mahdi Asgari. “Unlike previously proposed single-layer intelligent surfaces, these volumetric metacrystals can be designed to control multiple incoming signals or frequency bands independently—a key requirement for realistic wireless communication.”

Did this star eat its planets? A new study offers clues on ‘chemical paradox’ of a binary system

Astronomers have investigated a puzzling binary star system in which two stars that may have formed together now show dramatically different chemical compositions. The new study, uploaded to the arXiv preprint server on May 29, hints at the possibility that one of the stars may have swallowed its own planets.

Generally, in binary systems, the two stars form from the same molecular cloud and, as a result, have the same age and chemical composition. Any differences in their metallicity, astronomers say, hint at an event involving mass transfer or engulfment of planetary components or other internal processes. HD 81,809 is one such peculiar system in which the stars are both sun-like G stars but are at different stages of evolution.

The primary star, HD 81809A, has crossed the main-sequence phase, depleted its hydrogen fuel in the core but hasn’t turned into a giant star yet—it is now a subgiant. On the other hand, the secondary star, HD 81809B, is still a main-sequence star. It has lithium enrichment and there is a difference in iron content between the two stars—the primary is metal-poor with an iron abundance of −0.57 dex, while the secondary has roughly solar metallicity around 0.00 dex.

New semiconductor building blocks make power converters smaller, more affordable

Researchers at the Department of Energy’s Oak Ridge National Laboratory incorporated gallium nitride semiconductors to create a high-efficiency power converter that is more compact, affordable, and efficient.

A power converter is a type of device that manages semiconductor switching and transforms current or voltage, so electricity flows smoothly and safely among equipment, power sources, and users.

Silicon semiconductors are the fundamental building blocks of conventional converters. Manufacturer ROHM Semiconductor provided the ORNL research team with gallium nitride semiconductors that enable switching 10 to 20 times faster than silicon while losing less energy in the process.

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