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Category: cosmology

Using the Low Frequency Array (LOFAR), European astronomers have investigated a galaxy cluster designated CIZA J2242.8+5301, dubbed the Sausage cluster. The observations conducted at very low radio frequencies provide more insights into the properties of radio relics in this cluster. The new findings are presented in a research paper published May 29 on the arXiv preprint server.

Galaxy clusters consist of up to thousands of galaxies bound together by gravity. They are the largest known gravitationally-bound structures in the universe, and therefore serve as excellent laboratories for studying galaxy evolution and cosmology. Observations show that galaxy clusters generally form as a result of mergers and grow by accreting sub-clusters.

CIZA J2242.8+5301 is a well-studied merging at a redshift of 0.192. It contains prominent double radio relics (diffuse, elongated radio sources of synchrotron origin) and other diffuse radio sources. CIZA J2242.8+5301 was nicknamed the Sausage cluster due to the distinctive morphology of its northern relic.

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Astronomers from the University of Hawaiʻi’s Institute for Astronomy (IfA) have discovered the most energetic cosmic explosions yet discovered, naming the new class of events “extreme nuclear transients” (ENTs). These extraordinary phenomena occur when massive stars—at least three times heavier than our sun—are torn apart after wandering too close to a supermassive black hole. Their disruption releases vast amounts of energy visible across enormous distances.

The team’s findings appear in the journal Science Advances.

“We’ve observed stars getting ripped apart as tidal disruption events for over a decade, but these ENTs are different beasts, reaching brightnesses nearly ten times more than what we typically see,” said Jason Hinkle, who led the study as the final piece of his doctoral research at IfA. “Not only are ENTs far brighter than normal tidal disruption events, but they remain luminous for years, far surpassing the of even the brightest known supernova explosions.”

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Physicists are always searching for new theories to improve our understanding of the universe and resolve big unanswered questions.

But there’s a problem. How do you search for undiscovered forces or particles when you don’t know what they look like?

Take . We see signs of this mysterious cosmic phenomenon throughout the universe, but what could it possibly be made of? Whatever it is, we’re going to need new physics to understand what’s going on.

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The Big Bang is often described as the explosive birth of the universe—a singular moment when space, time and matter sprang into existence. But what if this was not the beginning at all? What if our universe emerged from something else—something more familiar and radical at the same time?

In a new paper, published in Physical Review D, my colleagues and I propose a striking alternative. Our calculations suggest the Big Bang was not the start of everything, but rather the outcome of a gravitational crunch or collapse that formed a very massive black hole—followed by a bounce inside it.

This idea, which we call the black hole , offers a radically different view of cosmic origins, yet it is grounded entirely in known physics and observations.

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The Big Bang is often described as the explosive birth of the universe – a singular moment when space, time and matter sprang into existence. But what if this was not the beginning at all? What if our universe emerged from something else – something more familiar and radical at the same time?

In a new paper, published in Physical Review D, my colleagues and I propose a striking alternative. Our calculations suggest the Big Bang was not the start of everything, but rather the outcome of a gravitational crunch or collapse that formed a very massive black hole – followed by a bounce inside it.

This idea, which we call the black hole universe, offers a radically different view of cosmic origins, yet it is grounded entirely in known physics and observations.

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Across the cosmos, many stars can be found in pairs, gracefully circling one another. Yet one of the most dramatic pairings occurs between two orbiting black holes, formed after their massive progenitor stars exploded in supernova blasts. If these black holes lie close enough together, they will ultimately collide and form an even more massive black hole.

Sometimes a black hole is orbited by a neutron star—the dense corpse of a star also formed from a supernova explosion but which contains less mass than a black hole. When these two bodies finally merge, the black hole will typically swallow the neutron star whole.

To better understand the extreme physics underlying such a grisly demise, researchers at Caltech are using supercomputers to simulate black hole–neutron star collisions. In one study appearing in The Astrophysical Journal Letters, the team, led by Elias Most, a Caltech assistant professor of theoretical astrophysics, developed the most detailed simulation yet of the violent quakes that rupture a neutron star’s surface roughly a second before the black hole consumes it.

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A new study has revealed a novel effect caused by dark photons—hypothetical particles thought to make up a portion of the universe’s elusive dark matter. This discovery, made within the framework of Einstein–Cartan–Holst gravity, provides new insights into the fundamental interactions between matter and gravity.

The study was conducted by Prof. Gao Zhifu from the Xinjiang Astronomical Observatory of the Chinese Academy of Sciences, in collaboration with Dr. Luiz Carlos Garcia de Andrade from the State University of Rio de Janeiro, Brazil. Their findings, which include the first identification of a key physical quantity known as the Barbero–Immirzi (BI) parameter induced by dark photons, are published in The European Physical Journal C.

A large portion of the universe is filled with invisible matter known as , and the dark photon is one of its leading theoretical candidates. As a hypothetical particle beyond the Standard Model, the dark photon exhibits electromagnetic-like interactions through kinetic mixing with the ordinary photon. Unlike photons, however, dark photons possess mass and interact much more weakly with charged particles.

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Wormholes are a popular feature in science fiction, the means through which spacecraft can achieve faster-than-light (FTL) travel and instantaneously move from one point in spacetime to another. And while the General Theory of Relativity forbids the existence of “traversable wormholes,” recent research has shown that they are actually possible within the domain of quantum physics.

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