Latest news with #KAGRA
India Today
29-05-2025
- Science
- India Today
IIT-Bombay astronomers hunt for light from biggest explosions in space
A team of scientists at IIT-Bombay is searching the skies for a rare cosmic phenomenon — flashes of light that might come from the collision of black holes and neutron explosions are among the most violent events in the universe, and the team hopes to find clues that could change how we understand project is led by Professor Varun Bhalerao from the Physics Department at IIT-B. His team is exploring whether black holes, which are known for pulling in everything around them including light, can also emit light when they collide — a mystery yet to be When massive objects like black holes or neutron stars crash into each other, they create gravitational waves — ripples in space and time, first predicted by Albert Einstein. While detectors like LIGO in the US, Virgo in Europe, and KAGRA in Japan can pick up these waves, spotting light from such events is far 2017, scientists have only seen light and gravitational waves together from one kind of event: the merger of two neutron stars. No light has yet been seen from crashes involving black holes investigate further, IIT-B's researchers used India's space telescope AstroSat. Its CZTI instrument looked for X-rays that might have flashed within seconds of about 70 known gravitational wave events. These included black hole collisions up to 32 billion light-years far, the team hasn't spotted any flashes. But even these 'misses' help — they allow scientists to set limits on how bright such explosions might be, which sharpens future universe is the most extreme physics laboratory,' said Prof. Bhalerao. 'Looking for light from black hole collisions challenges what we think we know — and could lead to surprises.'With the upcoming LIGO India facility and India's proposed Daksha mission, designed to scan the whole sky for such flashes, scientists are the current global gravitational wave search continues until late 2025, more data may finally shed light on these dark cosmic events.
Yahoo
15-05-2025
- Science
- Yahoo
Black Hole Mergers Show Strange Mathematical Link to String Theory
A decade ago astrophysicists at the Laser Interferometer Gravitational-Wave Observatory (LIGO), operated by the California Institute of Technology and the Massachusetts Institute of Technology, managed to detect subtle ripples in spacetime called gravitational waves, released by a pair of black holes spiraling into each other, for the first time. That impressive discovery—which earned the 2017 Nobel Prize in Physics—has since become commonplace, with researchers regularly detecting gravitational waves from myriad far-distant celestial sources. And as the numbers of gravitational-wave observations have increased, physicists' careful modeling is revealing new details about their mysterious origins. Some of the most intriguing gravitational-wave events, it turns out, could arise not from catastrophic collisions but rather from near misses. Furthermore, these cosmic close calls might be best understood using concepts derived from string theory—a notional theory of everything that posits that all of nature is fundamentally composed of countless, wriggling subatomic strings. This arguably marks the first linkage to date between a core mathematical aspect of the arcane theory and real-world astrophysics. At least, that's the conclusion of an international team of researchers that applied geometric structures inspired by particle physics and string theory to the behavior of black holes when the colossal objects closely pass and deflect each other. Such interactions between black holes or neutron stars (compact remnants of exploded massive stars) can be studied through the deflection angle, the energy released through the near miss and the momentum of the objects' recoil—all of which may be discerned in gravitational waves. The team's results were published in the journal Nature on Wednesday. [Sign up for Today in Science, a free daily newsletter] In their study, the researchers used an obscure class of abstract mathematical functions to solve the formidable equations involved in determining the radiated energy from a near miss. 'You need these new functions, which, in math and mathematical physics, have been studied intensively but, to date, have not appeared in any real physical observable. That's what makes it quite interesting,' says Jan Plefka, a theoretical physicist at the Humboldt University of Berlin and a co-author of the new study. Those obscure functions, known as six-dimensional Calabi-Yau manifolds, had never been shown as directly relevant to descriptions of real astrophysical phenomena before. In the years since LIGO's initial detection, two additional major gravitational-wave observatories, Europe's Virgo and Japan's Kamioka Gravitational-Wave Detector (KAGRA), have come online. Together, they form the international LIGO-Virgo-KAGRA collaboration and have amassed detections of nearly 300 gravitational-wave events over the past decade, mostly from colliding pairs of black holes. Also called black hole 'mergers,' such events are the cacophonous moment when these dense gravitational behemoths smash together to form a single, larger beast. Plefka and his colleagues are studying different interactions known as 'scattering' events, which occur when paired black holes slip by each other, usually in prelude to their eventual coalescence. During these close encounters, the clashing gravity of the black holes causes each to accelerate past the other, generating a significant gravitational-wave signal, but the objects are sufficiently separated to avoid merging. It's no coincidence that this resembles elementary particles deflecting each other. 'You can use the techniques developed for the scattering of microscopic objects to describe this scattering of macroscopic ones,' Plefka says. Considered from far enough away, well beyond the event horizon—that pivotal region within which neither matter nor light can escape—a black hole can be modeled as a particlelike point with mass and spin, albeit one that generates gravitational rather than electromagnetic waves. On that basis, Plefka and his colleagues applied techniques from quantum field theory that are more typically used to analyze the behavior of elementary particles. 'We're building on decades of work that has been done to make predictions for collider experiments,' says Gustav Mogull, a particle physicist at Queen Mary University of London and one of Plefka's co-authors. The team's goal was to bring its numerical approximations as close as possible to mirroring reality—which, of course, tends to be more messy. To do that, Mogull, Plefka and their team toiled to crank up the complexity of their calculations. In this work, the researchers incorporated five levels of that complexity—to what is known as the fifth post-Minkowskian order of precision—for describing the scattering angles of black hole pairs, their radiated energies and their recoils. This is where the Calabi-Yau geometric structures, normally associated with string theory, come in. In string theory, Calabi-Yau geometries involve the compactification of higher dimensions. Here, they are not merely abstractions but instead emerge from the researchers' calculations of black hole scattering. It's perhaps ironic that string theory, notoriously derided as untestable, has given rise to mathematical structures of relevance to measurable physics far from the rarefied realm of strings. Any mathematical function is associated with some kind of geometry, Mogull explains—and as the function increases in complexity, so, too, does its geometry. In the case of something basic, such as the sine or cosine functions used in trigonometry, that geometry is a simple circle. Elliptic functions, on the other hand, imply a doughnut-shaped geometry called a torus, which is also a Calabi-Yau onefold. It turns out that the functions Mogull, Plefka and their team developed for black hole scattering are associated with Calabi-Yau threefold structures, which involve six-dimensional surfaces. 'I don't think the appearance of Calabi-Yaus was that unexpected within our community. I would say this represents confirmation of something that people had suspected but was yet to be verified,' Mogull says. To demonstrate the utility of their approach in their study, Plefka, Mogull and their colleagues compare their approximations of black hole scattering angles to other, presumably more precise ones that were derived from numerical simulations. Such simulations can be time-consuming to run, even on state-of-the-art supercomputers—hence the search for accurate approximations. The team's highest-order approximation closely matches the results of supercomputer number crunching for cases of black holes that gently deflect each other across great distances. But when the black holes come closer to a head-on collision, the team's calculations begin diverging from the numerical simulations. Such work may seem to be a purely academic exercise, but in fact, the research could prove vital for making new discoveries. Signals from scattering black holes and neutron stars should be within reach of the next generation of gravitational-wave detectors that are set to come online in the late 2030s. These detectors, which will also need a new generation of models called waveform templates to discern true gravitational-wave signals from a sea of cosmic and terrestrial noise, include the proposed Einstein Telescope in Europe and Cosmic Explorer in the U.S. The latter, like LIGO, is supported by the National Science Foundation, and so far these kinds of gravitational-wave projects have avoided being directly targeted by the Trump administration's aggressive proposed cuts to federally funded science. The work's prospect for enhancing our understanding of gravitational-wave sources excites scientists who are gearing up for this new wave of detectors. They include Jocelyn Read, a physicist at California State University, Fullerton, who works with the Cosmic Explorer project. 'Next-generation facilities can measure nearby signals with exquisite fidelity,' she says. (Here 'nearby' means 'within a few billion light-years.') 'So having very accurate and precise predictions from our current theories is definitely needed to test them against those kinds of future observations,' Read adds. Yet she also urges caution when assessing the significance of Plefka, Mogull and their colleagues' work. 'If they're talking about implications for gravitational-wave astronomy, there are a few more steps that are needed,' she says. And their team has competitors, too, including some who have been deploying numerical simulations of their own. These kinds of approximate methods could eventually inform the waveform templates that are so crucial for filtering out noise in upcoming gravitational-wave detectors, Plefka says. Geraint Pratten, a LIGO physicist at the University of Birmingham in England, agrees. 'I think it's a heroic calculation by the group. It will provide a lot of insight into how we can structure next-generation waveform models,' he says. Pratten adds that more work will need to be done to move past the new study's limitations. For example, the paper focuses on black holes without spin and those that undergo 'unbound' scattering, which means that they deflect each other and never meet again. In reality, most, if not all, black holes are thought to spin, and usually scattering events precede an eventual merger. But in any case, he believes some gravitational waves from black hole and neutron star deflections will eventually be detectable, such as through observations of globular clusters, where these dense objects are packed together in a small space, cosmically speaking. For Plefka, Mogull and their peers, this macroscopic version of quantum field theory is still a young field, and there are many new types of astrophysically relevant calculations that they and others can do. These esoteric Calabi-Yau structures, formerly on the frontier of theoretical physics, could be just the beginning. 'You've had this whole new class of mathematical functions—these theoretical things that had appeared in string theory,' Mogull says. 'And we're saying, 'Look, this is tangible. This [radiated energy from scattering] is something you can try to detect, try to measure. This is real physics now.''
Scientific American
14-05-2025
- Science
- Scientific American
Deep Math from String Theory Appears in Clashing Black Holes
A decade ago astrophysicists at the Laser Interferometer Gravitational-Wave Observatory (LIGO), operated by the California Institute of Technology and the Massachusetts Institute of Technology, managed to detect subtle ripples in spacetime called gravitational waves, released by a pair of black holes spiraling into each other, for the first time. That impressive discovery—which earned the 2017 Nobel Prize in Physics—has since become commonplace, with researchers regularly detecting gravitational waves from myriad far-distant celestial sources. And as the numbers of gravitational-wave observations have increased, physicists' careful modeling is revealing new details about their mysterious origins. Some of the most intriguing gravitational-wave events, it turns out, could arise not from catastrophic collisions but rather from near misses. Furthermore, these cosmic close calls might be best understood using concepts derived from string theory—a notional theory of everything that posits that all of nature is fundamentally composed of countless, wriggling subatomic strings. This arguably marks the first linkage to date between a core mathematical aspect of the arcane theory and real-world astrophysics. At least, that's the conclusion of an international team of researchers that applied geometric structures inspired by particle physics and string theory to the behavior of black holes when the colossal objects closely pass and deflect each other. Such interactions between black holes or neutron stars (compact remnants of exploded massive stars) can be studied through the deflection angle, the energy released through the near miss and the momentum of the objects' recoil—all of which may be discerned in gravitational waves. The team's results were published in the journal Nature on Wednesday. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. Black Holes as Particles In their study, the researchers used an obscure class of abstract mathematical functions to solve the formidable equations involved in determining the radiated energy from a near miss. 'You need these new functions, which, in math and mathematical physics, have been studied intensively but, to date, have not appeared in any real physical observable. That's what makes it quite interesting,' says Jan Plefka, a theoretical physicist at the Humboldt University of Berlin and a co-author of the new study. Those obscure functions, known as six-dimensional Calabi-Yau manifolds, had never been shown as directly relevant to descriptions of real astrophysical phenomena before. In the years since LIGO's initial detection, two additional major gravitational-wave observatories, Europe's Virgo and Japan's Kamioka Gravitational-Wave Detector (KAGRA), have come online. Together, they form the international LIGO-Virgo-KAGRA collaboration and have amassed detections of nearly 300 gravitational-wave events over the past decade, mostly from colliding pairs of black holes. Also called black hole 'mergers,' such events are the cacophonous moment when these dense gravitational behemoths smash together to form a single, larger beast. Plefka and his colleagues are studying different interactions known as 'scattering' events, which occur when paired black holes slip by each other, usually in prelude to their eventual coalescence. During these close encounters, the clashing gravity of the black holes causes each to accelerate past the other, generating a significant gravitational-wave signal, but the objects are sufficiently separated to avoid merging. It's no coincidence that this resembles elementary particles deflecting each other. 'You can use the techniques developed for the scattering of microscopic objects to describe this scattering of macroscopic ones,' Plefka says. Considered from far enough away, well beyond the event horizon—that pivotal region within which neither matter nor light can escape—a black hole can be modeled as a particlelike point with mass and spin, albeit one that generates gravitational rather than electromagnetic waves. On that basis, Plefka and his colleagues applied techniques from quantum field theory that are more typically used to analyze the behavior of elementary particles. 'We're building on decades of work that has been done to make predictions for collider experiments,' says Gustav Mogull, a particle physicist at Queen Mary University of London and one of Plefka's co-authors. Closer to Complex Realities The team's goal was to bring its numerical approximations as close as possible to mirroring reality—which, of course, tends to be more messy. To do that, Mogull, Plefka and their team toiled to crank up the complexity of their calculations. In this work, the researchers incorporated five levels of that complexity—to what is known as the fifth post-Minkowskian order of precision—for describing the scattering angles of black hole pairs, their radiated energies and their recoils. This is where the Calabi-Yau geometric structures, normally associated with string theory, come in. In string theory, Calabi-Yau geometries involve the compactification of higher dimensions. Here, they are not merely abstractions but instead emerge from the researchers' calculations of black hole scattering. It's perhaps ironic that string theory, notoriously derided as untestable, has given rise to mathematical structures of relevance to measurable physics far from the rarefied realm of strings. Any mathematical function is associated with some kind of geometry, Mogull explains—and as the function increases in complexity, so, too, does its geometry. In the case of something basic, such as the sine or cosine functions used in trigonometry, that geometry is a simple circle. Elliptic functions, on the other hand, imply a doughnut-shaped geometry called a torus, which is also a Calabi-Yau onefold. It turns out that the functions Mogull, Plefka and their team developed for black hole scattering are associated with Calabi-Yau threefold structures, which involve six-dimensional surfaces. 'I don't think the appearance of Calabi-Yaus was that unexpected within our community. I would say this represents confirmation of something that people had suspected but was yet to be verified,' Mogull says. To demonstrate the utility of their approach in their study, Plefka, Mogull and their colleagues compare their approximations of black hole scattering angles to other, presumably more precise ones that were derived from numerical simulations. Such simulations can be time-consuming to run, even on state-of-the-art supercomputers—hence the search for accurate approximations. The team's highest-order approximation closely matches the results of supercomputer number crunching for cases of black holes that gently deflect each other across great distances. But when the black holes come closer to a head-on collision, the team's calculations begin diverging from the numerical simulations. The Road Ahead Such work may seem to be a purely academic exercise, but in fact, the research could prove vital for making new discoveries. Signals from scattering black holes and neutron stars should be within reach of the next generation of gravitational-wave detectors that are set to come online in the late 2030s. These detectors, which will also need a new generation of models called waveform templates to discern true gravitational-wave signals from a sea of cosmic and terrestrial noise, include the proposed Einstein Telescope in Europe and Cosmic Explorer in the U.S. The latter, like LIGO, is supported by the National Science Foundation, and so far these kinds of gravitational-wave projects have avoided being directly targeted by the Trump administration's aggressive proposed cuts to federally funded science. The work's prospect for enhancing our understanding of gravitational-wave sources excites scientists who are gearing up for this new wave of detectors. They include Jocelyn Read, a physicist at California State University, Fullerton, who works with the Cosmic Explorer project. 'Next-generation facilities can measure nearby signals with exquisite fidelity,' she says. (Here 'nearby' means 'within a few billion light-years.') 'So having very accurate and precise predictions from our current theories is definitely needed to test them against those kinds of future observations,' Read adds. Yet she also urges caution when assessing the significance of Plefka, Mogull and their colleagues' work. 'If they're talking about implications for gravitational-wave astronomy, there are a few more steps that are needed,' she says. And their team has competitors, too, including some who have been deploying numerical simulations of their own. These kinds of approximate methods could eventually inform the waveform templates that are so crucial for filtering out noise in upcoming gravitational-wave detectors, Plefka says. Geraint Pratten, a LIGO physicist at the University of Birmingham in England, agrees. 'I think it's a heroic calculation by the group. It will provide a lot of insight into how we can structure next-generation waveform models,' he says. Pratten adds that more work will need to be done to move past the new study's limitations. For example, the paper focuses on black holes without spin and those that undergo 'unbound' scattering, which means that they deflect each other and never meet again. In reality, most, if not all, black holes are thought to spin, and usually scattering events precede an eventual merger. But in any case, he believes some gravitational waves from black hole and neutron star deflections will eventually be detectable, such as through observations of globular clusters, where these dense objects are packed together in a small space, cosmically speaking. For Plefka, Mogull and their peers, this macroscopic version of quantum field theory is still a young field, and there are many new types of astrophysically relevant calculations that they and others can do. These esoteric Calabi-Yau structures, formerly on the frontier of theoretical physics, could be just the beginning. 'You've had this whole new class of mathematical functions—these theoretical things that had appeared in string theory,' Mogull says. 'And we're saying, 'Look, this is tangible. This [radiated energy from scattering] is something you can try to detect, try to measure. This is real physics now.''
Yahoo
06-03-2025
- Science
- Yahoo
Unproven Einstein theory of 'gravitational memory' may be real after all, new study hints
When you buy through links on our articles, Future and its syndication partners may earn a commission. A team of theoretical physicists has proposed a new way to test one of the most intriguing predictions of Einstein's theory of general relativity: gravitational memory. This effect refers to a permanent shift in the fabric of the universe caused by the passage of space-time ripples known as gravitational waves. Although these waves have already been detected by observatories such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo interferometer, the waves' lingering imprint remains elusive. The researchers suggest that the cosmic microwave background — a faint glow left over from the Big Bang — might carry the signatures of powerful gravitational waves from distant black hole mergers. Studying these signals could not only confirm Einstein's prediction but also shed light on some of the most energetic events in the universe's history. "The observation of this phenomenon can provide us with more knowledge of different fields of physics," Miquel Miravet-Tenés, a doctoral student at the University of Valencia and a co-author of the study, told Live Science via email. "Since it is a direct prediction of Einstein's theory of general relativity, its observation would serve as a confirmation of the theory, much like the observation of gravitational waves by LIGO, Virgo and KAGRA [the Kamioka Gravitational Wave Detector] has done! It can also be used as an additional tool to study some astrophysical scenarios, since it can contain information about the type of events that generate memory, such as supernovae or black hole collisions." According to general relativity, massive objects warping space-time can generate ripples that travel across the universe at the speed of light. These gravitational waves arise when massive bodies accelerate, such as when two black holes spiral inward and merge. Unlike ordinary waves that pass through matter and leave it unchanged, gravitational waves can permanently alter the structure of space-time itself. This means that any objects they pass through, including elementary particles of light known as photons, may experience a lasting change in velocity or direction. As a result, the light traveling across the cosmos could carry a memory of past gravitational-wave events imprinted in its properties. Related: 'Einstein's equations need to be refined': Tweaks to general relativity could finally explain what lies at the heart of a black hole The researchers explored whether this effect could be observed in the cosmic microwave background — a relic radiation field that has been traveling through space since the universe was just a fraction of a percent of its current age. Subtle shifts in the temperature of this radiation could hold clues about gravitational waves from ancient black hole mergers. "We can learn plenty of things," Kai Hendriks, a doctoral student at the Niels Bohr Institute at the University of Copenhagen and another co-author of the study, told Live Science in an email. "For example, measuring gravitational memory in a gravitational wave signal gives us more information about the properties of the two black holes that produced this signal; how heavy those black holes were or how far away they are from us." But the implications extend beyond individual black hole mergers. If the imprint of gravitational memory can be detected in the cosmic microwave background, it could reveal whether supermassive black holes merged more frequently in the early universe than they do today. This could offer new insight into how galaxies and black holes have evolved over cosmic time. To determine whether the memory effect could be detected, the team calculated how black hole mergers influence the cosmic microwave background. Their analysis showed that these violent events should leave behind measurable changes in the background radiation, with the strength of the signal depending on how massive the black holes were and how frequently such mergers occurred throughout history. "The wavelength of light is directly related to its temperature — small wavelength means high temperature and large wavelength means low temperature," David O'Neill, a doctoral student at the Niels Bohr Institute and another co-author of the study, told Live Science in an email. "Some of the light affected by the gravitational wave memory becomes 'hotter' while some of the other light becomes 'colder.' The regions of hot and cold light form a kind of pattern in the sky. We predict this pattern to be present in the cosmic microwave background, albeit quite faint." Although current telescopes that are capable of detecting microwave radiation, such as the Planck satellite, have mapped the cosmic microwave background in exquisite detail, the temperature shifts caused by gravitational wave memory are expected to be extremely small — on the order of a trillionth of a degree. This makes them difficult to observe with existing technology. However, future telescopes with greater sensitivity may be able to detect these subtle distortions, providing a new way to probe the invisible gravitational influences that have shaped the universe. While the study demonstrates that gravitational wave memory should leave a trace in the cosmic microwave background, the researchers acknowledge that their calculations were based on simplified assumptions. More refined models will be needed before definitive predictions can be made. RELATED STORIES —'Cosmic Horseshoe' may contain black hole the size of 36 billion suns — one of the largest ever detected —Scientists may have just discovered 300 of the rarest black holes in the universe —'We were amazed': Astronomers discover oldest, biggest black hole jet in the known universe — and there may be more For instance, the team initially assumed that all merging black holes had the same mass, whereas in reality, their masses can vary significantly. Supermassive black holes range from a few million to tens of billions of times the mass of the sun, meaning that their influence on the cosmic microwave background will also differ. Accounting for this variation will be important in future studies. "Right now, the effect we're studying is incredibly subtle. However, it's possible that in certain regions of the sky, it could be unexpectedly strong," Hendriks said. "To explore this, we need more advanced models that take into account the entire evolution of the universe. So not an easy task! But this could bring us closer to detecting this cosmic imprint and uncovering new insights into the evolution of the universe."
