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Category: cosmology – Page 42

Scientists detect two giant black holes flashing light a billion light-years away.

Astronomers have identified two giant black holes causing strange flashes of light at about one billion light years away from Earth. The flashes or light bursts are occurring at regular intervals, but what’s causing them is even more surprising.

The researchers suggest that the black hole pair is swirling within a vast cloud of gas, and their interaction with the gas cloud is actually sparking the unusual flashes —- marking it as the first observation of its kind.

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A recent study in Physical Review Letters explores quantum effects on black hole thermodynamics and geometry, focusing on extending two classical inequalities into the quantum regime.

Black holes have been thoroughly studied through a classical approach based on Einstein’s general theory of relativity. However, this approach does not account for quantum effects like Hawking radiation.

The goal of the study was for the researchers to refine classical theories by including quantum effects, thereby offering an improved understanding of black hole dynamics.

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Researchers at UC Berkeley proposed that axions, hypothetical particles, could be detected shortly after a supernova’s gamma rays. They suggest that the Fermi Gamma-ray Space Telescope has a 1 in 10 chance of observing this phenomenon. Axions would be produced during the early moments of a star’s collapse and would then transform into high-energy gamma rays in the star’s magnetic field.

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Astronomers have made a groundbreaking discovery of binary star systems, consisting of a white dwarf and a main sequence star, within young star clusters.

This discovery opens up new avenues for understanding stellar evolution and could provide insights into the origins of phenomena such as supernovas and gravitational waves.

Breakthrough Discovery in Star Clusters.

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Low-frequency radio observations could allow researchers to distinguish among several dark matter models, thanks to dark matter’s influence on the early Universe.

The profusion of dark matter candidates reflects how easy it is for any of them to explain the current large-scale structure of the Universe. Decisive clues about dark matter’s true nature are more likely to appear at earlier epochs. Unfortunately, those clues are harder to observe. Now Jo Verwohlt of the University of Copenhagen in Denmark and her collaborators have shown how a deeply redshifted hydrogen line could unmask dark matter [1]. To do so, they also identified confounding signatures from regular, baryonic matter.

Some theories posit that dark matter interacts with so-called dark radiation. In the dense early Universe, the heating effect of that interaction could have been enough for large concentrations of dark matter known as halos to temporarily and repeatedly resist gravitational collapse. Termed dark acoustic oscillations (DAOs), these cycles of expansion and collapse would have quickly died out. But before they did, they could have affected the onset of “cosmic dawn.” That’s when the first galaxies formed from primordial gas drawn into the halos.

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The search for the universe’s dark matter could end tomorrow—given a nearby supernova and a little luck. The nature of dark matter has eluded astronomers for 90 years, since the realization that 85% of the matter in the universe is not visible through our telescopes. The most likely dark matter candidate today is the axion, a lightweight particle that researchers around the world are desperately trying to find.

Astrophysicists at the University of California, Berkeley, now argue that the axion could be discovered within seconds of the detection of gamma rays from a nearby supernova explosion. Axions, if they exist, would be produced in copious quantities during the first 10 seconds after the core collapse of a massive star into a neutron star, and those axions would escape and be transformed into in the star’s intense magnetic field.

Such a detection is possible today only if the lone gamma-ray telescope in orbit, the Fermi Gamma-ray Space Telescope, is pointing in the direction of the supernova at the time it explodes. Given the telescope’s field of view, that is about one chance in 10.

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Scientists have now performed one such large-scale test by using DESI. They observed almost 6 million galaxies and quasars, which are bright hearts of galaxies powered by feeding supermassive black holes. Perhaps unsurprisingly, this test, which has traced the evolution of the universe since it was around 3 billion years old, has once again shown general relativity to be the right “recipe” for gravity.

“General relativity has been very well tested at the scale of solar systems, but we also needed to test that our assumption works at much larger scales,” study co-leader and the French National Center for Scientific Research (CNRS) cosmologist Pauline Zarrouk said in a statement. “Studying the rate at which galaxies formed lets us directly test our theories and, so far, we’re lining up with what general relativity predicts at cosmological scales.”

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Located a staggering 160,000 light-years from us, the star WOH G64 was imaged thanks to the impressive sharpness offered by the European Southern Observatory’s Very Large Telescope Interferometer (ESO’s VLTI). The new observations reveal a star puffing out gas and dust in the last stages before it becomes a supernova.

“For the first time, we have succeeded in taking a zoomed-in image of a in a galaxy outside our own Milky Way,” says Keiichi Ohnaka, an astrophysicist from Universidad Andrés Bello in Chile.

“We discovered an egg-shaped cocoon closely surrounding the star,” says Ohnaka, the lead author of a study reporting the observations published today in Astronomy & Astrophysics. “We are excited because this may be related to the drastic ejection of material from the dying star before a supernova explosion.”

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For decades, scientists have used the Milky Way as a model for understanding how galaxies form. But three new studies raise questions about whether the Milky Way is truly representative of other galaxies in the universe.

“The Milky Way has been an incredible physics laboratory, including for the physics of galaxy formation and the physics of dark matter,” said Risa Wechsler, the Humanities and Sciences Professor and professor of physics in the School of Humanities and Sciences. “But the Milky Way is only one system and may not be typical of how other galaxies formed. That’s why it’s critical to find similar galaxies and compare them.”

To achieve that goal, Wechsler cofounded the Satellites Around Galactic Analogs (SAGA) Survey dedicated to comparing galaxies similar in mass to the Milky Way.

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