An infographic showing the binary binary black hole merger that produced the GW231123 signal. | Photo Credit: Simona J. Miller/CaltechGravitational waves from monstrous black hole merger detected USING US National Science Foundation–funded observatories, the LIGO-Virgo-KAGRA (LVK) Collaboration has detected gravitational waves (GWs) arising from the merger of the most massive black holes ever observed. The powerful merger produced a final black hole approximately 225 times the solar mass. Designated GW231123, the GW signal, travelling from 2-13 billion light years away, was detected during the fourth observation run of the LVK network (which began in May 2023) on November 23, 2023.A prresentation on GW231123 was made at the 24th International Conference on General Relativity and Gravitation and the 16th Edoardo Amaldi Conference on GWs, which were held jointly in Glasgow, Scotland, UK, on July 14–18.The Laser Interferometer Gravitational-wave Observatory (LIGO) made history in 2015 when it made the first-ever direct detection of GWs, ripples in space-time. The waves in that detection had emanated from a black hole merger that resulted in a final black hole 62 times the solar mass. Since then, the LIGO team has teamed up with partners at the Virgo detector in Italy and the Kamioka Gravitational Wave Detector (KAGRA) in Japan to form the LVK Collaboration. These detectors have collectively observed about 300 black hole mergers since the first run in 2015.The most massive black hole merger before the present one—detected in 2021 and called GW190521—had a total mass of 140 times the solar mass. The GW231123 event was the result of coalescence of black holes of about 100 and 140 times the solar mass respectively.In addition to their huge masses, the black holes are also spinning rapidly, near the limit allowed by Einstein’s theory of general relativity. “This is the most massive BH [black hole] binary we’ve observed through GWs, and it presents a real challenge to our understanding of BH formation,” said Mark Hannam of Cardiff University. “BHs this massive are forbidden through standard stellar evolution models. One possibility is that the two BHs in this binary formed through earlier mergers of smaller BHs.”The high mass and extremely rapid spinning of the black holes in GW231123 push the limits of both GW detection technology and current theoretical models. Extracting accurate information from the signal required the use of models that account for the intricate dynamics of highly spinning black holes. “It’s an excellent case study for pushing forward the development of our theoretical tools,” said Charlie Hoy of the University of Portsmouth. According to Sophie Bini of Caltech, the event pushes instrumentation and data analysis capabilities to the edge of what is currently possible.Also Read | Surprise merger in deep spaceWhy do we need sleep? The answer may lie in mitochondria. | Photo Credit: AleksandarGeorgiev/Getty ImagesWhy do we need sleep?A NEW study from the University of Oxford has unravelled how a metabolic “overload” in specialised brain cells triggers the need to sleep. The study, led by Gero Miesenböck and Raffaele Sarnataro, was published in the latest issue of Nature.Sleep is thus not merely rest for the mind; it is essential for maintaining the body’s power supply. According to the Oxford researchers, their study (using fruit flies) has shown that pressure to sleep arises from a build-up of electrical stress in the tiny energy generators inside brain cells. The key lies in mitochondria, the microscopic structures inside cells that use oxygen to convert food into energy. This provides a physical explanation for the biological drive to sleep and could reshape our understanding about sleep, ageing, and neurological disease.When the mitochondria of certain sleep-regulating brain cells become overcharged, they start to leak electrons, producing potentially damaging byproducts known as reactive oxygen species. This leak appears to act as a warning signal that drives the brain into sleep, restoring equilibrium before the damage spreads more widely.Specialised neurons act like circuit breakers. They measure this electron leak and trigger sleep when a threshold is crossed. By manipulating the energy handling in these cells—by either increasing or decreasing electron flow—the researchers could directly control how much the flies slept.Even replacing electrons with energy from light (using proteins borrowed from microorganisms) had the same effect: more energy, more leak, more sleep.“We set out to understand what sleep is for, and why we feel the need to sleep at all. Despite decades of research, no one had identified a clear physical trigger. Our findings show that the answer may lie in the very process that fuels our bodies: aerobic metabolism,” Miesenböck said.The findings help explain well-known links between metabolism, sleep, and lifespan. Smaller animals, which consume more oxygen per gram of body weight, tend to sleep more and live shorter lives. Humans with mitochondrial diseases often experience debilitating fatigue even without exertion, now potentially explained by the same mechanism.“This research answers one of biology’s big mysteries,” said Sarnataro. “Why do we need sleep? The answer appears to be written into the very way our cells convert oxygen into energy.”Also Read | While you are asleep, your brain flushes out wasteIn most organisms, a protein-pigment complex called Photosystem II kick-starts photosynthesis by trapping energy from sunlight and splitting water, providing oxygen molecules and supplying electrons that get transported to other proteins and molecules. | Photo Credit: Shubham Basera/IIScUnravelling a mystery in photosynthesisRESEARCHERS at the Indian Institute of Science (IISc), Bengaluru, and Caltech, California, have solved a long-standing mystery involving the first steps of photosynthesis, the fundamental process by which plants, algae, and some bacteria trap energy from sunlight to produce oxygen and chemical energy. The study has been published in Proceedings of the National Academy of Sciences.Photosynthesis involves a series of chain reactions in which electrons are transferred across multiple pigment molecules. Although well-studied, it is not fully understood for several reasons: the components involved are too many and too complex, energy transfer happens at ultra-fast speeds, and different organisms carry it out slightly differently.In most organisms, a protein-pigment complex called Photosystem II (PSII) kick-starts photosynthesis by trapping energy from sunlight and splitting water, providing oxygen molecules and supplying electrons that get transported to other proteins and molecules.PSII contains two identical arms, D1 and D2, around which four chlorophyll molecules and two pheophytins—pigments related to chlorophyll—are symmetrically arranged. These arms are also linked to electron-carrier molecules called plastoquinones. Electrons flow first from chlorophyll to pheophytin, then from pheophytin to plastoquinone. But, despite the apparent structural symmetry between D1 and D2, electrons seem to flow only along D1. Hitherto, it was not clear why these initial electron movements that are critical for energy transfer happen across only one arm of the protein-pigment complex.Using a combination of molecular dynamics simulations, quantum mechanical calculations, and a well-known theory for electron transfer to map the energy landscape for electron movement in both branches, the researchers assessed the efficiency of electron transfer through the two branches.The team found that the D2 branch has a much higher energy barrier, which makes electron transport from pheophytin to plastoquinone energetically unfavourable. The researchers also simulated the current-voltage characteristics of both branches and found that the resistance against electron movement in D2 was two orders of magnitude higher than that in D1.The asymmetry in electron flow may be influenced by subtle differences in the protein environment around PSII and how the pigments are embedded in it, the researchers suggested. For example, the chlorophyll pigment in D1 has an excitation state at a lower energy than its D2 counterpart, suggesting that the D1 pigment has a better chance of attracting and transferring electrons.“Our research presents a significant step forward in understanding natural photosynthesis,” the IISc release quotes Prabal K. Maiti, one of the authors of the study, as saying. “These findings may help design efficient artificial photosynthetic systems capable of converting solar energy into chemical fuels, contributing to innovative and sustainable renewable energy solutions.”CONTRIBUTE YOUR COMMENTS