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Neutrons Illuminate the Magnetic Dance of Chiral Phonons

Neutron scattering has provided a new and broader view of the twirling collective atomic vibrations in a magnetic crystal.

Phonons—quantized conveyors of sound and heat in solids—are usually visualized as collective vibrations in which atoms simply bounce back and forth, almost as if they were weights on springs. However, atoms can sometimes form “chiral phonons” that twirl and swivel clockwise or counterclockwise, in a way that resembles a coordinated dance [1]. When these circular, chiral motions entrain ionic charge, they generate a magnetic moment, which suggests that there might be a way to control sound and heat using magnetic fields. Until recently, this magnetic dance was primarily observed using optical techniques, granting access to only one corner of the “stage”—the point in the phonon’s momentum space where the momentum is nearly zero. Song Bao of Nanjing University in China and his collaborators have now broadened the view of momentum space by using inelastic neutron spectroscopy.

NASA’s MAVEN detects first evidence of lightning-like activity on Mars

While sifting through the extensive data collected by NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft over the last decade, scientists discovered a familiar type of electromagnetic signal commonly caused by lightning. This rare find represents the first direct indication of lightning activity on Mars. The team recently published their findings in Science Advances, where they describe the event and why it’s so difficult to detect lightning-like activity on Mars.

Whistler waves are low-frequency radio wave signals generated by lightning, which create an impulse that propagates through a planet’s magnetosphere, following along the magnetic field lines. The whistler waves disperse due to the slower velocity of the lower frequencies through the plasma of the ionosphere and magnetosphere. These waves are typical on Earth, but have also been observed on Jupiter, Saturn and Neptune. All of these planets all possess strong magnetic fields and corresponding magnetospheres, facilitating the movement of whistler waves.

Mars, on the other hand, does not have a global, Earth-like magnetic field. This is because the internal activity that causes these magnetic fields ceased on Mars billions of years ago. This may contribute to the fact that lightning-like discharges in the Martian atmosphere have not yet been observed. But lightning-like activity on Mars is not impossible.

3D printing with moon dirt for lunar habitats

“By combining different feedstocks, like metal and ceramics, in the printing process, we found that the final material is really sensitive to the environment,” said Sizhe Xu. [ https://www.labroots.com/trending/space/30260/3d-printing-mo…habitats-2](https://www.labroots.com/trending/space/30260/3d-printing-mo…habitats-2)

How can lunar regolith be used to construct future habitats on the Moon? This is what a recent study published in Acta Astronautica hopes to address as a team of scientists investigated novel methods for using lunar regolith for making structures on the lunar surface. This study has the potential to help scientists, engineers, mission planners, and future astronauts develop methods for working and living on the Moon, which comes as NASA’s Artemis program plans to land humans on the Moon in 2028.

For the study, the researchers examined how a laser 3D printing method called laser directed energy deposition (LDED) could be used for manufacturing structures using lunar simulant under a myriad of environments, specifically lunar conditions of zero atmosphere, oxygen, and complete vacuum. The lunar simulant used for the experiments is known as LHS-1 (lunar highland regolith simulants), with the lunar highlands being the lighter-colored mountainous regions of the Moon as seen from Earth, as opposed to the volcanic regions of the Moon that are darker in appearance.

Along with the environmental conditions, the researchers also examined how printing LHS-1 on various types of surfaces yielded different results. They also examined laser speed, scanning power, and the final microstructure products. In the end, the researchers found that alumina-silicate ceramic surfaces and high temperatures produced the most promising structures but cautioned that laboratory conditions vary from the real-world environment on the Moon.

MeerKAT discovers record-breaking cosmic laser halfway across the universe

Astronomers using the MeerKAT radio telescope in South Africa have discovered the most distant hydroxyl megamaser ever detected. It is located in a violently merging galaxy more than 8 billion light-years away, opening a new radio astronomy frontier.

Hydroxyl megamasers are natural “space lasers”—extremely bright radio-wavelength emissions produced when hydroxyl molecules in gas-rich, merging galaxies crash into one another. These cosmic collisions compress gas and stimulate large reservoirs of hydroxyl molecules to amplify radio emission.

The physical mechanism is very similar to lasers on Earth, but operates at a much longer wavelength of light of about 18 centimeters, rather than the optical light that our eyes can see. When this special radio light is exceptionally bright, it is termed a megamaser—a “cosmic beacon” that can be seen across vast stretches of the universe.

Astronomers shocked by how these giant exoplanets formed

JWST just found evidence that some “super-Jupiters” may have formed like planets, not failed stars. A distant star system with four super-sized gas giants has revealed a surprise. Thanks to JWST’s powerful vision, astronomers detected sulfur in their atmospheres — a chemical clue that they formed like Jupiter, by slowly building solid cores. That’s unexpected because these planets are far bigger and orbit much farther from their star than models once allowed.

Gas giants are enormous planets made primarily of hydrogen and helium. They may contain dense central cores, but unlike Earth, they do not have solid surfaces you could stand on. In our solar system, Jupiter and Saturn are classic examples. Beyond our neighborhood, astronomers have identified many gas giant exoplanets, some far larger than Jupiter. The most massive of these worlds begin to resemble brown dwarfs, substellar objects sometimes called “failed stars” because they do not fuse hydrogen.

This overlap raises a major question in astronomy. How exactly do these massive planets form? One possibility is core accretion, the same process believed to have created Jupiter and Saturn. In this scenario, a solid core slowly builds up inside a disk of dust and ice, gathering rocky and icy material until it becomes massive enough to pull in surrounding gas. Another possibility is gravitational instability, where a swirling cloud of gas around a young star collapses quickly under its own gravity, forming a large object more like a brown dwarf.

Simulations show a path to ‘ideal glass’ with crystal-like entropy

The types of glass that we encounter in everyday life, such as window glass or smartphone screens, are disordered solids. This means that they consist of particles locked in place, like those in solids, but arranged randomly, similarly to how they would be in a liquid.

Almost a century ago, Walter Kauzmann, who was a chemistry professor at Princeton University at the time, was confronted with the possible existence of a so-called ideal glass, an amorphous system with the entropy of a crystal. This is a glass in which particles are still arranged randomly, but the particles fill space so efficiently that there is only one possible arrangement, as opposed to the many disordered arrangements of conventional glass.

Kauzmann’s theoretical proposals inspired numerous other physicists to explore the idea of this perfectly equilibrated glass. Previous studies suggested that this elusive state could not be reached using conventional cooling processes.

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