Blazars are some of the brightest objects in the cosmos. They are composed of a supermassive black hole.
A black hole is a place in space where the gravitational field is so strong that not even light can escape it. Astronomers classify black holes into three categories by size: miniature, stellar, and supermassive black holes. Miniature black holes could have a mass smaller than our Sun and supermassive black holes could have a mass equivalent to billions of our Sun.
Greer and Ivanov agree that existing, albeit limited, data on tetrataenite’s magnetic properties suggest that it may not match high-performance neodymium-based magnets. But the researchers maintain that optimization of the tetrataenite casting process could improve its magnetic properties and thus make it a worthwhile option. “It is good to have a wider range of permanent magnet materials, because that allows better balancing of such factors as magnetic performance and environmental impact,” Greer says. “A one-for-one swap with rare-earth magnets is not necessarily the goal.”
For now, the team has demonstrated how to make a piece of tetrataenite, but they say that future work will focus on how to consolidate many pieces into a bulk magnet. “The analogy here would be that we have shown we can make a brick—a piece of tetrataenite—but not yet a house—a magnet,” Greer says.
Beyond materials science, the researchers hint that this work may even impact astrophysics research as scientists reconsider how long it takes for tetrataenite to develop in a meteorite and how fast the cooling rate is in that space environment.
An international team of astronomers have turned a new technique onto a group of galaxies and the faint light between them—known as ‘intra-group light’—to characterize the stars that dwell there.
Lead author of the study published in MNRAS, Dr. Cristina Martínez-Lombilla from the School of Physics at UNSW Science, said We know almost nothing about intra-group light.
The brightest parts of the intra-group light are ~50 times fainter than the darkest night sky on Earth. It is extremely hard to detect, even with the largest telescopes on Earth—or in space.
Black holes continue to be equal parts terrifying and fascinating.
An underrated NASA telescope reveals the mechanics behind some supermassive black holes’ relativistic jets.
Physicists have long struggled to explain why the Universe started out with conditions suitable for life to evolve. Why do the physical laws and constants take the very specific values that allow stars, planets, and ultimately life to develop?
The expansive force of the Universe, dark energy, for example, is much weaker than theory suggests it should be – allowing matter to clump together rather than being ripped apart.
A common answer is that we live in an infinite multiverse of Universes, so we shouldn’t be surprised that at least one Universe has turned out as ours. But another is that our Universe is a computer simulation, with someone (perhaps an advanced alien species) fine-tuning the conditions.
An international team of astrophysicists has made a puzzling discovery while analyzing certain star clusters. The University of Bonn played a major role in the study. The finding challenges Newton’s laws of gravity, the researchers write in their publication. Instead, the observations are consistent with the predictions of an alternative theory of gravity. However, this is controversial among experts. The results have now been published in the Monthly Notices of the Royal Astronomical Society.
In their work, the researchers investigated the so-called open star clusters. These are formed when thousands of stars are born within a short time in a huge gas cloud. As they “ignite,” the galactic newcomers blow away the remnants of the gas cloud. In the process, the cluster expands considerably. This creates a loose formation of several dozen to several thousand stars. The weak gravitational forces acting between them hold the cluster together.
“In most cases, open star clusters survive only a few hundred million years before they dissolve,” explains Prof. Dr. Pavel Kroupa of the Helmholtz Institute of Radiation and Nuclear Physics at the University of Bonn. In the process, they regularly lose stars, which accumulate in two so-called “tidal tails.” One of these tails is pulled behind the cluster as it travels through space. The other, in contrast, takes the lead like a spearhead.
A team of researchers from Friedrich-Schiller-Universität Jena, Università di Torino and INFN sezione di Torino, has found evidence that the black hole collision that led to an odd gravitational wave detection in 2019 was due to a unique set of circumstances. In their paper published in the journal Nature Astronomy, the group describes modeling and simulating the conditions that could possibly lead to the unique gravitational wave signature.
The development of gravitational wave detectors has led to a better understanding of what happens when black holes collide. In most instances, the data has shown, they occur due to binary stars exploding and then slowly spiraling toward one another until they meet at a gravitational center and merge.
But then, on May 21, 2019, gravitational waves were detected from two black holes merging, but the data showed that neither of the black holes appeared to be spinning and the duration of the signal was shorter than all the others that have been detected. The odd signal left astrophysicists scratching their heads. Now, in this new effort, the researchers believe they have come up with a plausible explanation for the observation.
The collective motion of animals in a group is a fascinating topic of research for many scientists. Understanding these collective behaviors can sometimes inspire the development of strategies for promoting positive social change, as well as technologies that emulate nature.
Many studies describe flocking behavior as a self-organized process, with individuals in a group continuously adapting their direction and speed to ultimately achieve a “collective” motion. This perspective, however, does not consider the hierarchical structure exhibited by many animal groups and the possible benefits of having a “leader” guide the way.
Luis Gómez-Nava, Richard Bon and Fernando Peruani, three researchers at Université Côte d’Azur, Université de Toulouse, and CY Cergy Paris Université have recently used physics theory to examine the collective behavior of small flocks of sheep. Their findings, published in Nature Physics, show that by alternating between the role of leader and follower, the flock ultimately achieves some form of “collective intelligence.”
“Neutron stars apparently behave a bit like chocolate pralines”.
Neutron stars were first discovered more than 60 years ago, but very little is known about the interior of neutron stars, the incredibly compact cores of dead stars.
According to their findings, a press statement reveals, they bear a surprising resemblance to chocolate pralines.
Sakkmesterke/iStock.
Researchers have discovered the heaviest-known bound isotope of sodium and characterized other neutron-rich isotopes, offering important benchmarks for refining nuclear models.
The neutron dripline marks a boundary of nuclear existence—indicating isotopes of a given element with a maximum number of neutrons. Adding a neutron to a dripline isotope will cause the isotope to become unbound and release one or more of its neutrons. Mapping the dripline is a major goal of modern nuclear physics, as this boundary is a testing ground for nuclear models and has implications for our understanding of neutron stars and of the synthesis of elements in stellar explosions. Now studies by two groups extend our knowledge of the properties of nuclei close to the dripline [1, 2]. Working at the Radioactive Isotope Beam Factory (RIBF) in Japan, Deuk Soon Ahn of RIKEN and colleagues have discovered sodium-39 (39 Na), which likely marks the dripline location for the heaviest element to date (Fig. 1) [1].