The discovery of hidden stars known as dark dwarfs has sent shockwaves throughout the scientific community. These enigmatic objects have been linked to dark matter, one of the most debated topics in modern cosmology and astrophysics research. Dark matter is estimated to comprise approximately 25% of the universe’s mass-energy density, yet it remains invisible to our telescopes due to its non-emission of light.

“We think that 25% of the universe is composed of a type of matter that doesn’t emit light, making it invisible to our eyes and telescopes. We only detect it through its gravitational effects. That’s why we call it dark matter,” explains Jeremy Sakstein, Professor of Physics at the University of Hawai’i and one of the study’s authors.

The most well-known dark matter candidates are Weakly Interacting Massive Particles (WIMPs), which interact very weakly with ordinary matter and reveal themselves only through their gravitational effects. This type of dark matter would be necessary for dark dwarfs to exist, as it could be captured by stars and accumulate inside them.

Dark dwarfs emit light, but not due to nuclear fusion processes like ordinary stars. Instead, they shine faintly due to the energy produced by their relatively small gravitational contraction. However, if brown dwarfs are located in regions with abundant dark matter, they can transform into something else – dark dwarfs.

This entire hypothesis relies on a specific type of dark matter, where heavy particles interact strongly with each other and annihilate into visible energy. Sakstein and colleagues propose a distinctive marker for identifying dark dwarfs: the presence of Lithium-7. This element burns easily and is quickly consumed in ordinary stars, making it a unique effect that can be used to distinguish between brown dwarfs and dark dwarfs.

Tools like the James Webb Space Telescope might already be able to detect extremely cold celestial objects like dark dwarfs. However, Sakstein suggests another possibility: looking at a whole population of objects and asking, statistically, if it is better described by having a sub-population of dark dwarfs or not.

If in the coming years we manage to identify one or more dark dwarfs, how strong would that clue be in support of the hypothesis that dark matter is made of WIMPs? Reasonably strong. With light dark matter candidates, something like an axion, I don’t think you’d be able to get something like a dark dwarf. They don’t accumulate inside stars. If we manage to find a dark dwarf, it would provide compelling evidence that dark matter is heavy, interacts strongly with itself, but only weakly with the Standard Model. This includes classes of WIMPs, but it would include some other more exotic models as well.

Atacamite, a vibrant emerald-green mineral found in the Atacama Desert in Chile, has been discovered to possess a rare property that defies conventional physics. The mineral exhibits magnetocaloric behavior at low temperatures, meaning its temperature changes significantly when subjected to a magnetic field. A team of researchers from TU Braunschweig and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has been investigating this phenomenon, and their findings could lead to the development of new materials for energy-efficient magnetic cooling.

The researchers found that atacamite’s unique geometric structure, consisting of long chains of small, linked triangles known as sawtooth chains, is responsible for its magnetocaloric behavior. This arrangement creates “magnetic frustration,” where the spins in the copper ions cannot align themselves antiparallel to one another due to the triangular structure. As a result, the spins only arrange themselves at very low temperatures (under 9 Kelvin) in a static alternating structure.

When the researchers applied an extremely high magnetic field to the atacamite crystal, something surprising occurred: the material exhibited a significant cooling effect, with its temperature dropping to almost half of its original value. This strong magnetocaloric effect has fascinated the researchers, as it is unusual for magnetically frustrated materials to exhibit such behavior.

Further studies using magnetic resonance spectroscopy have revealed that the magnetic order in atacamite is destroyed when a magnetic field is applied. This destruction of magnetic order explains why the material’s temperature changes significantly in response to the magnetic field. The team has also conducted complex numerical simulations, which have provided an explanation for the mineral’s unexpected behavior: the magnetic moments on the tips of the sawtooth chains mediate a weak coupling to neighboring chains, leading to the removal of long-range magnetic order.

The researchers believe that their work could inspire further research into innovative magnetocaloric materials within the class of magnetically frustrated systems. While atacamite itself is unlikely to be mined for use in cooling systems, its unique properties provide valuable insights into the fundamental mechanisms governing magnetic behavior in solids. The discovery of this rare property could potentially lead to breakthroughs in energy-efficient magnetic cooling technologies, revolutionizing the way we think about and use refrigeration.

The world is on the cusp of a revolution in agriculture and industry, thanks to a groundbreaking discovery by researchers at the University of Sydney. By harnessing the power of human-made lightning, they have developed a more efficient method for generating ammonia – one of the most important chemicals used in fertilizers that account for almost half of all global food production.

Traditionally, ammonia has been produced through the Haber-Bosch process, which requires large amounts of energy and relies on fossil fuels. This not only leaves a huge carbon footprint but also necessitates centralized production and long-distance transportation of the product. In contrast, the new method developed by Professor PJ Cullen and his team is a game-changer.

The plasma-based electrolysis system uses electricity to excite nitrogen and oxygen molecules in the air, which are then converted into ammonia gas through a membrane-based electrolyser. This two-step process has shown promising results, with the researchers successfully producing gaseous ammonia – a major breakthrough that opens up new possibilities for sustainable fertilizers.

The implications of this discovery are vast. Ammonia is not only essential for agriculture but also holds potential as a carbon-free fuel source and an effective means of storing and transporting hydrogen. The shipping industry has taken notice, recognizing the potential of ammonia to reduce greenhouse gas emissions.

As the world grapples with climate change and sustainability, this breakthrough provides a beacon of hope for a more environmentally friendly future. With further research and development, it’s clear that green ammonia is on the horizon – and it’s an exciting time for science, industry, and humanity alike.

Professor Cullen and his team are now working tirelessly to refine their method, pushing the energy efficiency of the electrolyzer component to make it more competitive with the Haber-Bosch process. This research has been published in Angewandte Chemie International Edition, a testament to the scientific community’s commitment to innovation and progress.

As we move forward into this new era of sustainable ammonia production, one thing is clear: the future of food, industry, and our planet are intertwined – and this breakthrough is a shining example of humanity’s capacity for innovation and collaboration.