Latest news with #GlobalPhysicsSummit
Yahoo
22-03-2025
- Science
- Yahoo
High-school student accidentally discovers black hole 'light echo' twice as wide as the Milky Way
When you buy through links on our articles, Future and its syndication partners may earn a commission. ANAHEIM, Calif. — Long after the black hole in the center of a galaxy sputters out, you can still see its ghost lingering in surrounding gas clouds aglow with leftover radiation, like wisps of smoke emanating from an already extinguished flame. Astronomers call these cosmic ghosts "light echoes" — and that's what high-school junior Julian Shapiro found while scanning the cosmos for supernova remnants. "There are these outer regions of gas being ionized by a supermassive black hole, which results in this echo," Shapiro said at a March 20 presentation here at the 2025 American Physical Society (APS) Global Physics Summit. Shapiro, 17, is a student at The Dalton School in New York City. But in between classes and scoping out potential colleges, he's also an independent astronomer who presents at global conferences like this week's APS meeting. Originally, Shapiro began sifting through the DECaPS2 survey — an inventory of the southern galactic plane from the Dark Energy Camera at the Cerro Tololo Inter-American Observatory in Chile — to find the debris of exploding stars in supernova remnants and planetary nebulas. But after zeroing in on one such object, he found its structure didn't match the wispy filaments characteristic of a supernova remnant, nor did it show evidence of a supernova at its center. "It was a real surprise to stumble upon this," Shapiro told Live Science. Related: High school students who came up with 'impossible' proof of Pythagorean theorem discover 9 more solutions to the problem The object, which he believes to be a light echo, stands in a field of potential supermassive black holes. Using measurements from the Southern African Large Telescope, he found high contents of oxygen and ionized sulfur sprinkled into the region — both indicators of shocked material. All of these signs suggest that the object is the afterglow of a now-dormant black hole, which once spewed radiation that ionized the surrounding gas, causing it to emit light even after the black hole quieted down. Shapiro currently pegs the light echo at about 150,000 to 250,000 light-years in diameter — about 1.5 to two times the width of the entire Milky Way galaxy. And if his estimates hold up, he thinks it could be a viable candidate for the largest light echo ever discovered. "This object covers a large area in the sky, which makes it a bit easier to get in-depth images of," Shapiro said. According to Sasha Plavin, a black hole researcher at Harvard University who was not involved in the research, echoes like the one Shapiro discovered can help us learn more about how black holes behave in the hearts of galaxies. "I really like how carefully [Shapiro] looked into these images," Plavin told Live Science. "These galactic events are always of interest, and I think these echoes are a great way of studying them." Plavin is also interested in seeing how this new light echo measures up to others — whether it occurred faster or slower than existing examples. "Putting this discovery in a wider context could be useful in the future," he said. RELATED STORIES —Unproven Einstein theory of 'gravitational memory' may be real after all, new study hints —Is our universe trapped inside a black hole? This James Webb Space Telescope discovery might blow your mind —Evidence for Stephen Hawking's unproven black hole theory may have just been found — at the bottom of the sea As Shapiro continues studying the light echo, he hopes to learn more about its composition with measurements of its different regions. But in the meantime, he's excited to continue contributing to black hole science — even if he came across it by accident. "My involvement in this area of research came as a bit of a surprise to me," he said. "But I hope this object, in particular, helps expand the knowledge of galaxy activities that we don't have too great of an understanding of."
WIRED
20-03-2025
- Science
- WIRED
Evidence Grows That Dark Energy Changes Over Time
Jennifer Ouellette, Ars Technica Mar 20, 2025 6:00 PM The latest Dark Energy Spectroscopic Instrument results fall short of the discovery threshold but strengthen evidence for dynamical dark energy. Last year, we reported on an exciting hint of new physics in the first data analysis results from the Dark Energy Spectroscopic Instrument (DESI)—namely that the dark energy, rather than being constant, might vary over time. Granted, those hints were still below the necessary threshold to claim discovery and hence fell under the rubric of 'huge, if true.' But now we have more data from DESI, combined with other datasets, and those hints have gotten significantly stronger—so much so that Mustapha Ishak-Boushaki of the University of Texas at Dallas, who co-chairs one of the DESI working groups, said that 'we are getting to the point of no return' for confirming dynamical dark energy. Ishak-Boushaki and several other DESI team members presented their results at the American Physical Society's Global Physics Summit today in Anaheim, California. Several relevant papers have also been posted to the physics arXiv. This story originally appeared on Ars Technica, a trusted source for technology news, tech policy analysis, reviews, and more. Ars is owned by WIRED's parent company, Condé Nast. Einstein's cosmological constant (lambda) implied the existence of a repulsive form of gravity. (For a more in-depth discussion of the history of the cosmological constant and its significance for dark energy, see our 2024 story.) Quantum physics holds that even the emptiest vacuum is teeming with energy in the form of 'virtual' particles that wink in and out of existence, flying apart and coming together in an intricate quantum dance. This roiling sea of virtual particles could give rise to dark energy, giving the universe a little extra push so that it can continue accelerating. The problem is that the quantum vacuum contains too much energy: roughly 10120 times too much. So the universe should be accelerating much faster than it is if the dark energy is, essentially, the cosmological constant. Still, all the observations to date indicate that it's constant. The best theoretical fit thus far is known as the Lambda CDM model, which incorporates both a weakly interacting cold dark matter and dark energy. One alternative theory proposes that the universe may be filled with a fluctuating form of dark energy dubbed 'quintessence.' There are also several other alternative models that assume the density of dark energy has varied over the history of the universe. In its earliest days, the universe was a hot, dense soup of subatomic particles, including hydrogen and helium nuclei, aka baryons. Tiny fluctuations created a rippling pattern through that early ionized plasma, which froze into a three-dimensional place as the universe expanded and cooled. Those ripples, or bubbles, are known as baryon acoustic oscillations (BAO). It's possible to use BAOs as a kind of cosmic ruler to investigate the effects of dark energy over the history of the universe. DESI is a state-of-the-art instrument that can capture light from up to 5,000 celestial objects simultaneously. Courtesy of Marilyn Sargent/Berkeley Lab That's what DESI was designed to do: take precise measurements of the apparent size of these bubbles (both near and far) by determining the distances to galaxies and quasars over 11 billion years. That data can then be sliced into chunks to determine how fast the universe was expanding at each point of time in the past, the better to model how dark energy was affecting that expansion. An Upward Trend Last year's results were based on analysis of a full year's worth of data taken from seven different slices of cosmic time and include 450,000 quasars, the largest ever collected, with a record-setting precision of the most distant epoch (between 8 to 11 billion years back) of 0.82 percent. While there was basic agreement with the Lamba CDM model, when those first-year results were combined with data from other studies (involving the cosmic microwave background radiation and Type Ia supernovae), some subtle differences cropped up. Essentially, those differences suggested that the dark energy might be getting weaker. In terms of confidence, the results amounted to a 2.6-sigma level for the DESI's data combined with CMB datasets. When adding the supernovae data, those numbers grew to 2.5-sigma, 3.5-sigma, or 3.9-sigma levels, depending on which particular supernova dataset was used. It's important to combine the DESI data with other independent measurements because 'we want consistency,' said DESI co-spokesperson Will Percival of the University of Waterloo. 'All of the different experiments should give us the same answer to how much matter there is in the universe at present day, how fast the universe is expanding. It's no good if all the experiments agree with the Lambda-CDM model, but then give you different parameters. That just doesn't work. Just saying it's consistent to the Lambda-CDM, that's not enough in itself. It has to be consistent with Lambda-CDM and give you the same parameters for the basic properties of that model.' These latest results cover the first three years of collected data, spanning almost 15 million galaxies and quasars. Once again, the DESI data alone was consistent with Lambda CDM, i.e., the dark energy is constant. And once again, when combined with other datasets—from CMB, supernovae, and weak gravitational lensing studies—strong hints emerged that dark energy might be changing over time. The confidence level ranges from 2.8 to 4.2 sigma, depending on the combination of datasets—just shy of the five-sigma threshold. This might strike the average citizen as an incremental advance, but the reality is more complicated. 'The DESI data itself is not incremental,' said Percival. 'We now have three years of data rather than one year of data. That is substantial, not just because of an increased area but because we've increased the overlap. The way we do the survey is we build up plates on the sky, and, after three years rather than one year of operations, we have a lot more of those overlaps filled in. So our data is a lot more complete in the sense that we've gone down to the full depth that we expect to get to in more patches. Consequently, our BAO measurements themselves are a lot better. They're between a factor of two and three better depending on exactly this balance between area versus depth.' A slice of the DESI data mapping celestial objects from Earth (center) to billions of light years away. Courtesy of Claire Lamman/DESI Collaboration Catherine Heymans, astronomer royal of Scotland, told Ars that these new results give scientists much more confidence in DESI's analysis. She was surprised at the excitement over last year's first results, since, 'whenever there's a first data release, the scientific community always takes the results with a pinch of salt,' she said. But DESI made its data public, and other scientists have been making their own analyses over the last year; it has stood up to that close scrutiny. 'The really strong significance for dynamical dark energy comes from the combination of the DESI standard ruler, the BAO plus the supernova data,' she added. 'That's two different ways of measuring the expansion rate of the universe. By combining those two things together, you get this strong detection of dynamical dark energy.' The next step for the DESI collaboration is to analyze five years' worth of data to see if the upward trend toward the 5-sigma threshold for discovery holds—perhaps even surpassing that threshold, which would be very exciting indeed. That will likely not happen for another two years, per Percival. Should 5 sigma be reached, Heymans said astronomers should expect to see similar results in data from the Euclid Space Telescope, which is slated to do a similar experiment to DESI, at higher redshift, in the near future. 'It opens up a huge range of possibilities,' said Percival of the implications should it be confirmed that dark energy changes over time. 'It will keep theorists happy for many years to come. As a scientist you want to sit a little bit on the fence. But if this is right, this is the next step after the discovery of dark energy. Lambda works. Now, Lambda doesn't work. It means there's a lot more information that's accessible about this process. I think people were worried that everything would show that it just exactly agrees with Lambda. But if there's actually things happening to how the acceleration is changing within detail, that's exciting because we can get a handle on the physics.' 'There's no fundamental underpinning for what could be causing that dynamical dark energy, and that does make me anxious,' said Heymans. 'It's like the observers are throwing the gauntlet back to the theorists. It'd be nice to be able to explain two dark entities with one fell swoop. I am excited about cracks in the cosmological model, because this way is pushing the theoretical community to think outside the box, to think of new ideas. And maybe that will solve the whole dark entity conundrum, which is why we're all here.' This story originally appeared on Ars Technica.
Yahoo
20-03-2025
- Science
- Yahoo
'The universe has thrown us a curveball': Largest-ever map of space reveals we might have gotten dark energy totally wrong
When you buy through links on our articles, Future and its syndication partners may earn a commission. Astronomers studying the largest-ever map of the cosmos have found hints that our best understanding of the universe is due a major rewrite. The analysis, which looked at nearly 15 million galaxies and quasars spanning 11 billion years of cosmic time, found that dark energy — the presumed-to-be constant force driving the accelerating expansion of our universe — could be weakening. Or at least this is what the data, collected by the Dark Energy Spectroscopic Instrument (DESI), suggest when combined with information taken from star explosions, the cosmic microwave background and weak gravitational lensing. If the findings hold up, it means that one of the most mysterious forces controlling the fate of our universe is even weirder than first thought — and that something is very wrong with our current model of the cosmos. The researchers' findings were published in multiple papers on the preprint server arXiv and presented March 19 at the American Physical Society's Global Physics Summit in Anaheim, California, so they have not yet been peer-reviewed. "It's true that the DESI results alone are consistent with the simplest explanation for dark energy, which would be an unchanging cosmological constant," co-author David Schlegel, a DESI project scientist at the Lawrence Berkeley National Laboratory in California, told Live Science. "But we can't ignore other data that extend to both the earlier and later universe. Combining [DESI's results] with those other data is when it gets truly weird, and it appears that this dark energy must be 'dynamic,' meaning that it changes with time." Dark energy and dark matter are two of the universe's most puzzling components. Together they make up roughly 95% of the cosmos, but because they do not interact with light, they can't be detected directly. Yet these components are key ingredients in the reigning Lambda cold dark matter (Lambda-CDM) model of cosmology, which maps the growth of the cosmos and predicts its end. In this model, dark matter is responsible for holding galaxies together and accounts for their otherwise inexplicably powerful gravitational pulls, while dark energy explains why the universe's expansion is accelerating. Related: Could the universe ever stop expanding? New theory proposes a cosmic 'off switch' But despite countless observations of these hypothetical dark entities shaping our universe, scientists are still unsure where they came from, or what they even are. Currently, the best theoretical explanation for dark energy is made by quantum field theory, which describes the vacuum of space as filled with a sea of quantum fields that fluctuate, creating an intrinsic energy density in empty space. In the aftermath of the Big Bang, this energy increases as space expands, creating more vacuum and more energy to push the universe apart faster. This suggestion helped scientists to tie dark energy to the cosmological constant — a hypothetical inflationary energy, growing with the fabric of space-time throughout the universe's life. Einstein named it Lambda in his theory of general relativity. "The problem with that theory is that the numbers don't add up," said Catherine Heymans, a professor of astrophysics at the University of Edinburgh and the Astronomer Royal for Scotland who was not involved in the study. "If you say: 'Well, what sort of energy would I expect from this sort of vacuum?' It's very, very, very, very different from what we measure," she told Live Science. "It's kind of exciting that the universe has thrown us a curveball here," she added. To figure out if dark energy is changing over time, the astronomers turned to three years' worth of data from DESI, which is mounted on the Nicholas U. Mayall 4-meter Telescope in Arizona. DESI pinpoints the monthly positions of millions of galaxies to study how the universe expanded up to the present day. By compiling DESI's observations, which includes nearly 15 million of the best measured galaxies and quasars (ultra-bright objects powered by supermassive black holes), the researchers came up with a strange result. Taken on their own, the telescope's observations are in "weak tension" with the Lambda-CDM model, suggesting dark energy may be losing strength as the universe ages, but without enough statistical significance to break with the model. But when paired with other observations, such as the universe's leftover light from the cosmic microwave background, supernovas, and the gravitational warping of light from distant galaxies, the likelihood that dark energy is evolving grows. In fact, it pushes the observations' disagreement with the standard model as far as 4.2 Sigma, a statistical measure on the cusp of the five-Sigma result physicists use as the "gold standard" for heralding a new discovery. Related: After 2 years in space, the James Webb telescope has broken cosmology. Can it be fixed? Whether this result will hold or fade over time with more data is unclear, but astrophysicists are growing confident that the discrepancy is less likely to disappear. RELATED STORIES —Cosmic voids may explain the universe's acceleration without dark energy —'Heavy' dark matter would rip our understanding of the universe apart, new research suggests —Something invisible and 'fuzzy' may lurk at the Milky Way's center, new research suggests "These data seem to indicate that either dark energy is becoming less important today, or it was more important early in the universe," Schlegel said. Astronomers say that further answers will come from a flotilla of new experiments investigating the nature of dark matter and dark energy in our universe. These include the Euclid space telescope, NASA's Nancy Grace Roman Space Telescope, and DESI itself, which is now in its fourth of five years scanning the sky and will measure 50 million galaxies and quasars by the time it's done. "I think it's fair to say that this result, taken at face-value, appears to be the biggest hint we have about the nature of dark energy in the [rough] 25 years since we discovered it," Adam Riess, a professor of astronomy at Johns Hopkins University who won the 2011 Nobel Prize in physics for his team's 1998 discovery of dark energy, told Live Science. "If confirmed, it literally says dark energy is not what most everyone thought, a static source of energy, but perhaps something even more exotic."
The Guardian
19-03-2025
- Science
- The Guardian
Dark energy: mysterious cosmic force appears to be weakening, say scientists
Dark energy, the mysterious force powering the expansion of the universe, appears to be weakening, according to a survey that could 'overthrow' scientists' current understanding of the fate of the cosmos. If confirmed, the results from the dark energy spectroscopic instrument (Desi) team at the Kitt Peak National Observatory in Arizona would have profound implications for theories about the evolution of the universe, opening up the possibility that its current expansion could eventually go into reverse in a 'big crunch'. A suggestion that dark energy reached a peak billions of years ago would also herald the first substantial change in decades to the widely accepted theoretical model of the universe. Prof Alexie Leauthaud-Harnett, a co-spokesperson for Desi and a cosmologist at the University of California, Santa Cruz, said: 'What we are seeing is deeply intriguing. It is exciting to think that we may be on the cusp of a major discovery about dark energy and the fundamental nature of our universe.' Dark energy was discovered in the late 1990s when astronomers used distant supernova explosions to investigate how the rate of cosmic expansion has changed over time. The expectation was that gravity should counteract the expansion that has been underway since the big bang, but instead, the supernovae indicated that the rate of expansion was accelerating, propelled by some unknown force that scientists called dark energy. Dark energy has been assumed to be a constant, which would imply the universe will meet its end in a desolate scenario called the 'big freeze', when everything is eventually so far apart that even light cannot bridge the gap between galaxies. The latest findings, announced on Thursday at the American Physical Society's Global Physics Summit in Anaheim, California, challenge that prevailing view. Desi uses its 5,000 fibreoptic 'eyes' to map the cosmos with unprecedented precision. Its latest data release captures 15m galaxies, spanning 11bn years of history, which astronomers have used to create the most detailed three-dimensional map of the universe to date. The results suggest that dark energy reached a peak in strength when the universe was about 70% of its current age and it is now about 10% weaker. This would mean the rate of expansion is still accelerating, but that dark energy is gently lifting its foot off the pedal. Prof Carlos Frenk, a cosmologist at the University of Durham and member of the Desi collaboration, said: 'What we're finding is that, yes, there is something pushing galaxies away from each other, but it is not constant. It is declining.' The results do not meet the so-called five-sigma threshold of statistical certainty that is the gold standard in physics for claiming a discovery. But many in the collaboration have shifted in recent months from a position of scepticism to confidently backing the finding. 'I'm not on the fence,' said Frenk. 'I've looked at the data carefully. To me, this is a robust result. We're witnessing the overthrow of the old paradigm and the emergence of a new paradigm.' Prof John Peacock, a cosmologist at the University of Edinburgh and a Desi collaborator who voiced scepticism about evolving dark energy at a Royal Society meeting last year, has been similarly persuaded. 'Extreme claims require extreme evidence,' he said. 'There's almost nothing in science that I would bet my house on. But I would put £1,000 on this result.' Others continue to reserve judgment. Prof George Efstathiou of the University of Cambridge, who was not involved in the findings, said: 'My take-home from this analysis is that the … measurements do not yet provide decisive evidence for evolving dark energy. They may do as Desi accumulates more data.' If dark energy keeps decreasing to the point where it becomes negative, the universe is predicted to end in a reverse big bang scenario known as the big crunch. Scientists do not know why dark energy, which is generally estimated to account for about 70% of the universe – with the rest made up of dark and ordinary matter – might be waning or whether this would indicate the laws of physics are changing or that a crucial component is missing from them. Prof Ofer Lahav, an astronomer at University College London and Desi collaborator, said: 'It's fair to say we have no idea what dark matter or dark energy is. The constant dark energy [theory] is already sufficiently challenging. I feel like: 'As if things were not complicated enough.' 'But you can also look at it more positively. For 20 years we've been stuck with dark energy. Now physicists have new questions.'
