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Category: cosmology – Page 310

It is a widely accepted theory today that when the first stars formed in our universe approximately 13 billion years ago, they quickly came together to form globular clusters. These clusters then coalesced to others to form the first galaxies, which have been growing through mergers and evolving ever since. For this reason, astronomers have long suspected that the oldest stars in the universe are to be found in globular clusters.

The study of in these clusters is therefore a means of determining the age of the universe, which is still subject to some guesswork. In this vein, an international team of astronomers and cosmologists recently conducted a study of globular clusters in order to infer the age of the universe. Their results indicate that the universe is about 13.35 billion years old, a result that could help astronomers learn more about the expansion of the cosmos.

Their study, titled “Inferring the Age of the Universe with Globular Clusters,” recently appeared online and was submitted for consideration to the Journal of Cosmology and Astroparticle Physics. The study was led by David Valcin, a predoctoral researcher from the Institute of Cosmos Sciences at the University of Barcelona (ICCUB), who was joined by a team from France, Spain, and the US.

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Using the Subaru Telescope, astronomers have identified two new dust-reddened (red) quasars at high redshifts. The finding, detailed in a paper published July 16 on the arXiv pre-print server, could improve the understanding of these rare but interesting objects.

Quasars, or quasi-stellar objects (QSOs), are extremely luminous active galactic nuclei (AGN) containing supermassive central black holes with accretion disks. Their redshifts are measured from the strong spectral lines that dominate their visible and ultraviolet spectra. Some QSOs are dust-reddened, hence dubbed red quasars. These objects have non-negligible amount of dust extinction, but are not completely obscured.

Astronomers are especially interested in finding new high– quasars (at redshift higher than 5.0) as they are the most luminous and most distant compact objects in the observable universe. Spectra of such QSOs can be used to estimate the mass of supermassive black holes that constrain the evolution and formation models of quasars. Therefore, high-redshift quasars could serve as a powerful tool to probe the early universe.

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A stunning flash of ultraviolet light from an exploding white dwarf has been detected by astronomers for only the second time, and could give researchers important clues about what spurs the demise of these ancient, spent stars.

Researchers became aware of this unusual supernova – called SN2019yvq – last December, only a day after the explosion took place. Within hours, scientists classified the event as a Type Ia supernova – not an unusual stellar event, ordinarily at least, except this time it was accompanied by the extremely rare flash of ultraviolet light.

“These are some of the most common explosions in the Universe,” says astrophysicist Adam Miller from Northwestern University.

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Scientists at Harvard University and the Black Hole Initiative (BHI) have developed a new method to find black holes in the outer solar system, and along with it, determine once-and-for-all the true nature of the hypothesized Planet Nine. The paper, accepted to The Astrophysical Journal Letters, highlights the ability of the future Legacy Survey of Space and Time (LSST) mission to observe accretion flares, the presence of which could prove or rule out Planet Nine as a black hole.

Dr. Avi Loeb, Frank B. Baird Jr. Professor of Science at Harvard, and Amir Siraj, a Harvard undergraduate student, have developed the new method to search for black holes in the outer solar system based on flares that result from the disruption of intercepted comets. The study suggests that the LSST has the capability to find black holes by observing for accretion flares resulting from the impact of small Oort cloud objects.

“In the vicinity of a black hole, small bodies that approach it will melt as a result of heating from the background accretion of gas from the interstellar medium onto the black hole,” said Siraj. “Once they melt, the small bodies are subject to tidal disruption by the black hole, followed by accretion from the tidally disrupted body onto the black hole.” Loeb added, “Because black holes are intrinsically dark, the radiation that matter emits on its way to the mouth of the black hole is our only way to illuminate this dark environment.”

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“Strange metals” have that name for a reason – these materials exhibit some unusual conductive properties and surprisingly, even have things in common with black holes. Now, a new study has characterized them in more detail, and found that strange metals constitute a new state of matter.

So-called strange metals differ from regular metals because their electrical resistance is directly linked to temperature. Electrons in strange metals are seen to lose their energy as fast as the laws of quantum mechanics allow. But that’s not all – their conductivity is also linked to two fundamental constants of physics: Planck’s constant, which defines how much energy a photon can carry, and Boltzmann’s constant, which relates the kinetic energy of particles in a gas with the temperature of that gas.

While these properties have been well observed over the years, scientists have had a hard time accurately modeling strange metals. So in a new study, researchers from the Flatiron Institute and Cornell University set out to solve the model, right down to absolute zero – lower than the lowest possible temperature for materials.

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“Not only does God play dice but… he sometimes throws them where they cannot be seen,” said Stephen Hawking about the paradoxical physics of black Holes. Welcome to the bizarre quantum world of “strange metals” –a new state of matter.

“The fact that we call them strange metals should tell you how well we understand them. Strange metals share remarkable properties with black holes, opening exciting new directions for theoretical physics,” says Olivier Parcollet, a senior research scientist at the Flatiron Institute’s Center for Computational Quantum Physics (CCQ), about the quantum world of metals that dissipate energy as fast as they’re allowed to under the laws of quantum mechanics. The electrical resistivity of a strange metal, unlike that of ordinary metals, is proportional to the temperature.

Even by the standards of quantum physicists, reports the Flatiron Institute, strange metals are just plain odd. Generating a theoretical understanding of strange metals is one of the biggest challenges in condensed matter physics. Now, using cutting-edge computational techniques, researchers from the Flatiron Institute and Cornell University have solved the first robust theoretical model of strange metals. The work reveals that strange metals are a new state of matter, the researchers report July 22 in the Proceedings of the National Academy of Sciences.

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Extreme Conditions

A metal’s electrical resistance, or how much it impedes the flow of electricity, is determined by a number of factors. But, according to the new research, if a superconducting metal — one that doesn’t impede electrical currents at all — is heated past the temperature at which it can still superconduct, it becomes a strange metal. At that point, its resistance is determined only by temperature and two fundamental constants — the same three factors that determine many qualities of a black hole.

“The fact that we call them strange metals should tell you how well we understand them,” Olivier Parcollet from the Flatiron Institute’s Center for Computational Quantum Physics said in a press release. “Strange metals share remarkable properties with black holes, opening exciting new directions for theoretical physics.”

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Even by the standards of quantum physicists, strange metals are just plain odd. The materials are related to high-temperature superconductors and have surprising connections to the properties of black holes. Electrons in strange metals dissipate energy as fast as they’re allowed to under the laws of quantum mechanics, and the electrical resistivity of a strange metal, unlike that of ordinary metals, is proportional to the temperature.

Generating a theoretical understanding of strange metals is one of the biggest challenges in condensed matter physics. Now, using cutting-edge computational techniques, researchers from the Flatiron Institute in New York City and Cornell University have solved the first robust theoretical model of strange metals. The work reveals that strange metals are a new state of matter, the researchers report July 22 in the Proceedings of the National Academy of Sciences.

“The fact that we call them strange metals should tell you how well we understand them,” says study co-author Olivier Parcollet, a senior research scientist at the Flatiron Institute’s Center for Computational Quantum Physics (CCQ). “Strange metals share remarkable properties with black holes, opening exciting new directions for theoretical physics.”

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Spiral galaxies such as our Milky Way can have sprawling magnetic fields. There are various theories about their formation, but so far the process is not well understood. An international research team has now analyzed the magnetic field of the Milky Way-like galaxy NGC 4217 in detail on the basis of radio astronomical observations and has discovered as yet unknown magnetic field structures. The data suggest that star formation and star explosions, so-called supernovae, are responsible for the visible structures.

The team led by Dr. Yelena Stein from Ruhr-Universität Bochum, the Centre de Données astronomiques de Strasbourg and the Max Planck Institute for Radio Astronomy in Bonn together with US-American and Canadian colleagues, published their report in the journal Astronomy and Astrophysics, released online on 21 July 2020.

The analyzed data had been compiled in the project “Continuum Halos in Nearby Galaxies”, where were utilized to measure 35 galaxies. “Galaxy NGC 4217 is of particular interest to us,” explains Yelena Stein, who began the study at the Chair of Astronomy at Ruhr-Universität Bochum under Professor Ralf-Jürgen Dettmar and who currently works at the Centre de Données astronomiques de Strasbourg. NGC 4217 is similar to the Milky Way and is only about 67 million light years away, which means relatively close to it, in the Ursa Major constellation. The researchers therefore hope to successfully transfer some of their findings to our home galaxy.

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