A strange, never-before-seen glow in the halo of our galaxy may be the strongest dark-matter breadcrumb yet.
A new analysis of 15 years’ worth of data from the Fermi Gamma-Ray Space Telescope reveals a glow of unusually high-energy gamma rays that cannot easily be attributed to any known source.
According to astronomer Tomonori Totani of the University of Tokyo in Japan, it may be the radiation produced when hypothetical dark matter particles collide and wipe out one another.
LHAASO has traced the mysterious cosmic ray “knee” to powerful micro-quasars firing ultra-energetic particles across the galaxy. LHAASO has uncovered that micro-quasars, black holes feeding on companion stars, are powerful PeV particle accelerators. Their jets produce ultra-high-energy gamma rays and protons that exceed long-held expectations. Precise cosmic-ray measurements reveal a new high-energy component, suggesting multiple sources within the Milky Way. These findings finally tie the “knee” structure to black hole jet systems.
Milestone results released by the Large High Altitude Air Shower Observatory (LHAASO) on November 16 have finally clarified a decades-old puzzle in astrophysics: the unusual drop in cosmic ray counts above 3 PeV that produces what scientists call the “knee” in the cosmic ray energy spectrum.
The cause of this steep decline has remained mysterious since it was first identified nearly 70 years ago. Researchers long suspected that the feature reflects the highest energies that cosmic ray sources can reach, marking a shift in the spectrum from one power-law behavior to another.
The quantum world is famously weird—a single particle can be in two places at once, its properties are undefined until they are measured, and the very act of measuring a quantum system changes everything. But according to new research published in Physical Review Letters, the quantum world is even stranger than previously thought.
What happens at the quantum level is in stark contrast to the classical world (what we see every day), where objects have definite properties whether or not we look at them, and observing them doesn’t change their nature. To see whether any system is behaving classically, scientists use a mathematical test called the Leggett-Garg inequality (LGI). Classical systems always obey the LGI limit while quantum systems violate it, proving they are non-classical.
In the early 1930s, Swiss astronomer Fritz Zwicky observed galaxies in space moving faster than their mass should allow, prompting him to infer the presence of some invisible scaffolding—dark matter—holding the galaxies together. Nearly 100 years later, NASA’s Fermi Gamma-ray Space Telescope may have provided direct evidence of dark matter, allowing the invisible matter to be “seen” for the very first time.
Dark matter has remained largely a mystery since it was proposed so many years ago. Up to this point, scientists have only been able to indirectly observe dark matter through its effects on observable matter, such as its ability to generate enough gravitational force to hold galaxies together.
The reason dark matter can’t be observed directly is that the particles that make up dark matter don’t interact with electromagnetic force—meaning dark matter doesn’t absorb, reflect or emit light.
Whether the Universe will ‘end’ at all is not certain, but all evidence suggests it will continue being humanity’s cosmic home for a very, very long time.
The Universe – all of space and time, and all matter and energy – began about 14 billion years ago in a rapid expansion called the Big Bang, but since then it has been in a state of continuous change.
First, it was full of a diffuse gas of particles that now make up atoms: protons, neutrons, and electrons. Then, that gas collapsed into stars and galaxies.
RAY-lee) is the scattering or deflection of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scattering medium (normal dispersion regime), the amount of scattering is inversely proportional to the fourth power of the wavelength (e.g., a blue color is scattered much more than a red color as light propagates through air). The phenomenon is named after the 19th-century British physicist Lord Rayleigh (John William Strutt). [ 1 ].
Photonic quantum processors, devices that can process information leveraging quantum mechanical effects and particles of light (photons), have shown promise for numerous applications, ranging from computations and communications to the simulation of complex quantum systems.
To be deployed in real-world settings, however, these photonic chips should reliably integrate many deterministic and indistinguishable single-photon sources on a single chip.
So far, achieving this has proved highly challenging. Most such photonic quantum chips developed so far utilize solid-state single-photon emitters that are limited by so-called spectral diffusion (i.e., the random “wandering” of their emission frequency).
Hydrogen in materials finds various applications such as hydrogen storage and heterogeneous catalysis (1–3). Hydrogen diffusion is an elementary step for hydrogen storage and reactions and has long been studied to date. Hydrogen, as the lightest and smallest atom, manifests nuclear quantum effects including the zero-point vibration, discrete vibrational energy levels, and quantum tunneling (4). These quantum effects are believed to have a substantial impact on diffusion at low temperatures.
The interaction of hydrogen with surroundings such as phonons and electrons of host materials can be crucial for the hydrogen tunneling. It has been theoretically suggested that whereas phonon effects associated with lattice deformation bring about a positive temperature dependence in the tunneling rate, the effect of nonadiabatic electron-hole pair excitation due to the presence of the Fermi surface causes a slightly negative temperature dependence in metals (5–10). From an experimental viewpoint, however, such temperature-dependent tunneling was rarely observed except for some cases of H on metal surfaces (11–19). As for three-dimensional systems, the tunneling was only mimicked by muon, a light isotope with about one-ninth the mass of H, in the spin relaxation experiments in simple metals (20–23). Detailed experimental data of the temperature-dependent hydrogen hopping rate at low temperatures in materials are still lacking to comprehensively elucidate the quantum nature of hydrogen.
Absorbed hydrogen in metals occupies interstitial lattice locations. Figure 1A illustrates the face-centered cubic (fcc) lattice structure, where tetrahedral (T) and/or octahedral (O) sites are preferred by hydrogen. Hydrogen atoms are known to thermally diffuse between stable sites via a metastable site at elevated temperatures. At low temperature, the quantum nature appears, and the tunneling between them might also play a decisive role. Although it is recognized that the potential shape is crucial for the tunneling rate (24), the influence of the interaction with surroundings on the tunneling in an asymmetric potential between inequivalent sites such as the stable and metastable sites has hardly been considered even theoretically (25). In this regard, experimental identification of the hopping pathway is also important to address the quantum nature of hydrogen.
