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Category: cosmology

A Steady Breeze from the Milky Way’s Black Hole

Astronomers may have solved a long-standing puzzle surrounding the giant black hole lurking at the center of our Galaxy, Sagittarius A* (Sgr A•. Using observations from the Atacama Large Millimeter/submillimeter Array (ALMA) radio observatory in Chile, Mark Gorski and Lena Murchikova of Northwestern University in Illinois have obtained signatures of a previously elusive wind from Sgr A* [1]. Such a wind had long been predicted but was never convincingly observed. If confirmed, the discovery could offer a rare glimpse into how the majority of supermassive black holes interact with their surroundings.

Supermassive black holes grow by accreting dust, stars, and gas in their vicinity. Nothing can escape the event horizon, but the turbulent environment outside of the horizon can propel gas outward in the form of jets and winds. Giant jets of plasma—such as the one emerging from M87*, the first black hole ever imaged—can be launched by twisted magnetic fields acting like cosmic slingshots. The same environment can drive less collimated outflows, or winds, through a combination of magnetic forces, thermal pressure, and radiation. Loosely speaking, “jets are to winds what laser pointers are to flashlights,” Gorski says.

Much of our understanding of these phenomena comes from the most extreme objects, such as quasars and active galactic nuclei, where winds and jets have been extensively documented. But most supermassive black holes, including Sgr A*, are thought to display less fireworks, living in quiescent, low-luminosity states that are far more difficult to study. Theory still predicts that these “quiet” black holes should fuel winds, but decades of observations of the closest black hole in the sky could not confirm such predictions. “The absence of a wind was one of the most uncomfortable things about our own Galaxy’s black hole,” Murchikova says.

To discover new physics, AI may need to ‘unlearn’ the old one

A study in the Journal of Cosmology and Astroparticle Physics explores how a machine-learning strategy known as transfer learning could dramatically reduce the computational cost of searching for new physics beyond the standard cosmological model—while also revealing an unexpected risk: Sometimes AI systems can become too reliant on what they already know.

Artificial intelligence is widely used in cosmology to analyze the universe. But testing theories beyond the standard cosmological model, known as ΛCDM, remains extremely computationally demanding.

Although ΛCDM successfully describes many properties of the universe—from its expansion to the distribution of galaxies—physicists know it is probably incomplete. Recent observations hint that phenomena such as massive neutrinos, modified gravity or evolving dark energy could point toward new physics beyond the current model.

Possible dark matter-deficient twins discovered in the Fornax Cluster

Astronomers have identified a possible new example of one of the universe’s strangest galaxy types: galaxies that appear to contain little or no dark matter. The newly studied pair, FCC 224 and FCC 240, on the outskirts of the Fornax Cluster, share several unusual traits with the only known pair of controversial dark-matter-deficient galaxies. The findings were uploaded to the arXiv preprint server on May 22.

Ultra-diffuse galaxies are faint systems that are roughly the size of the Milky Way but have much less mass, containing far fewer stars. They have sparked debate for more than 10 years, mainly because they have been observed with two contrasting levels of dark matter content.

On one end, the dark-matter-rich ultra-diffuse galaxies are reasonably well understood: These are thought to be “failed galaxies” quenched early, never building much stellar mass but holding on to many globular clusters. The opposite extreme is far stranger. A small number of ultra-diffuse galaxies appear to contain little or no dark matter at all, and the globular clusters they host are unusually bright.

Black hole feeding bursts may explain JWST’s Little Red Dots in early universe

A new theoretical study may have cracked one of the most puzzling discoveries of the James Webb Space Telescope (JWST): Little Red Dots, spotted across the early universe. The paper, posted to the arXiv preprint server on May 29, argues that these objects could be black holes caught in rare, violent bursts of feeding at a rate exceeding theoretical limits.

Since JWST began its survey of the deep universe, astronomers have been puzzled by a class of tiny, faint objects appearing in the early universe in far greater numbers than expected. They have a distinctive V-shaped spectrum—bright in both ultraviolet and optical light, but with a dip in between—along with broad emission lines hinting at active black holes. They also show an absence of X-ray, radio and infrared emission.

They don’t look like ordinary galaxies, and they don’t completely look like quasars, either. What they are has been an open question. Some researchers argue that Little Red Dots may need some outside-the-box physics to explain their origin and nature.

Quantum circuits help AI overcome memory limitations with minimal new parameters

For millions of people, chatbots powered by large language models (LLMs) are now a key feature of everyday life. These AI systems are growing at a rapid pace, but scaling them up is becoming increasingly costly and resource-intensive.

Through a new preprint on the arXiv server, a team led by Borja Aizpurua at Multiverse Computing in San Sebastián, Spain, has found a way to improve the performance of LLMs using quantum computing. Their approach could offer a smarter alternative, rather than simply throwing more hardware at the problem.

Magnetic Fields May Solve a Longstanding Binary Star Mystery

Magnetic fields may be the hidden force bringing both newborn stars and giant black holes together. New computer simulations suggest that magnetic fields play a crucial role in helping pairs of young stars form. The findings could explain why binary star systems are so common throughout the Milky

Scientists may have found the source of the most powerful neutrino ever detected

A record-shattering particle from deep space may have exposed some of the universe’s most extreme black hole engines. A mysterious particle from deep space has scientists buzzing after the most energetic neutrino ever detected slammed through the Mediterranean Sea. Now, researchers think they may have identified the cosmic “culprits” behind it: blazars — supermassive black holes blasting jets of matter straight toward Earth.

Three years ago, scientists detected something extraordinary deep beneath the Mediterranean Sea: the most energetic cosmic neutrino ever observed. The particle carried an astonishing energy of around 220 PeV, more than ten times greater than previously detected high energy neutrinos, and researchers still do not know exactly where it came from.

Now, a new study published in the Journal of Cosmology and Astroparticle Physics (JCAP) suggests the particle may have originated from blazars, some of the universe’s most extreme objects. Blazars are active galactic nuclei powered by supermassive black holes that shoot enormous jets of plasma directly toward Earth.

Milky Way black hole’s missing wind finally found after a half-century-long search

The hunt is over. After more than 50 years of searching, astrophysicists at Northwestern University have finally discovered evidence of a powerful wind blowing from the Milky Way’s central supermassive black hole, Sagittarius A* (Sgr A•.

According to theoretical physics and a long-accepted understanding of galaxies’ evolution, as black holes consume materials, they should produce wind or jets. Even a small amount of gas falling into a black hole should generate enough energy to push material outwards. Without wind, Sgr A* would be a unique outlier.

But, until now, no one could find it.

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