Latest news with #Zwicky
Indian Express
24-06-2025
- Science
- Indian Express
Dark matter mystery: Why there isn't no light yet after decades of search
In 1933, Swiss astrophysicist Fritz Zwicky was observing the Coma Cluster — a massive congregation of galaxies about 300 million light-years away — when he noticed something odd. The galaxies were swirling around each other far too fast. According to the visible matter in the cluster, they should have flown apart long ago. 'There must be some missing mass,' Zwicky concluded. Matter that was invisible, yet exerted a gravitational pull strong enough to hold the cluster together. He called it 'dunkle Materie,' or dark matter. Nearly a century later, that missing matter still haunts modern physics. We now know that everything we can see — stars, planets, gas, dust — makes up only about 5% of the universe. Another 27% is this elusive dark matter, which neither emits nor absorbs light, making it undetectable by traditional telescopes. Yet without it, galaxies would not hold together, and the cosmic web that binds the universe would fall apart. One of the most compelling clues to dark matter comes from the way galaxies move. Stars at the outer edges of spiral galaxies rotate much faster than expected — far too fast for the visible matter alone to account for. Without something unseen providing extra gravity, these galaxies should spin apart like leaves in a storm. Galaxy clusters, too, behave as if they are embedded in vast halos of invisible mass. Dark matter, then, acts like the hidden scaffolding of the cosmos — an unseen framework on which galaxies, clusters, and cosmic filaments are built. This gravitational scaffold shaped the formation of structure in the early universe and continues to hold it all together today. For a time, scientists hoped that neutrinos — extremely light, ghost-like particles that stream through the cosmos in unimaginable numbers — might be the missing glue. But although neutrinos do have mass, it's now clear that they move too fast and don't clump together the way dark matter must. Instead of forming scaffolding, they pass through matter like whispers, too fleeting to do the heavy lifting. The big question is: what is dark matter made of? For years, physicists hoped it was a new kind of particle. One popular idea was the WIMP — the weakly interacting massive particle. These hypothetical particles wouldn't interact with ordinary matter much, which is why we can't see them, but they would have mass and gravity. To find them, physicists built sensitive detectors in deep underground labs — shielded from cosmic rays and background radiation. These detectors waited for the rare event when a WIMP might bump into an atom. But so far, no unmistakable signal has emerged. One reason is that dark matter seems to interact with the rest of the universe through gravity alone, and not via electromagnetic or nuclear forces, making it extraordinarily difficult to catch in the act. As experiments continue to come up empty-handed, scientists are beginning to wonder whether our assumptions about the nature of dark matter might need to be revised—or whether it lies hidden in a realm we've yet to imagine. Another promising theory came from supersymmetry, a grand idea that predicted a heavier 'partner' for every known particle. Some of these partners, like the neutralino, seemed to be perfect dark matter candidates. But again, when the Large Hadron Collider turned on, these particles were nowhere to be found. It's now been decades, and dark matter still hasn't shown its face. One by one, the most obvious possibilities are being ruled out. The more massive, easier-to-detect particles haven't turned up. That's pushing researchers to think beyond the standard playbook — maybe dark matter consists of incredibly light particles like axions, or exists in a hidden 'dark sector' with its own forces. It's also possible we've been asking the wrong question. Some radical theories propose that our understanding of gravity itself may be incomplete — and that there is no dark matter at all. But so far, these modified gravity theories can't explain the full range of observations. The stakes are high. Solving the dark matter puzzle could change how we understand matter, forces, and the origin of structure in the cosmos. It may open doors to new physics beyond the Standard Model — our current best theory of particles and forces. But for now, dark matter remains a mystery. It doesn't shine, it doesn't collide, it doesn't leave fingerprints. And yet its gravitational pull shapes the largest structures in the universe. Perhaps the next generation of detectors will catch it. Perhaps the answer lies in a theory not yet imagined. Until then, we live in a universe where the majority of matter is invisible — felt, but not seen. As strange as that sounds, it may just be the universe's way of reminding us that our understanding is still incomplete, and that the cosmos is larger — and darker — than we ever imagined.
Yahoo
04-06-2025
- Science
- Yahoo
Astronomers detect most powerful explosions since Big Bang
At any given time across the universe, massive cosmic bodies are releasing incomprehensible amounts of energy. Stars burn like celestial nuclear fusion reactors, quasars emit thousands of times the luminosity of the Milky Way galaxy, and asteroids slam into planets. But all of these pale in comparison to a new class of events discovered by researchers at the University of Hawai'i's Institute for Astronomy (IfA). According to their findings published June 4 in the journal Science Advances, it's time to classify the universe's most energetic explosions as extreme nuclear transients–or ENTs. ENTs are as devastating as they are rare. They only occur when a massive star at least three times heavier than the sun drifts too close to a supermassive black hole. The colliding forces subsequently obliterate the star, sending out plumes of energy across huge swaths of space. Similar events known as tidal disruption events (TDEs) are known to occur on a (comparatively) smaller scale, and have been documented for over a decade. But ENTs are something else entirely. 'ENTs are different beasts,' study lead author and astronomer Jason Hinkle explained in an accompanying statement. 'Not only are ENTs far brighter than normal tidal disruption events, but they remain luminous for years, far surpassing the energy output of even the brightest known supernova explosions.' Hinkle was first tipped off to ENTs while looking into transients—longlasting flares that spew energy from a galaxy's center. Two particularly strange examples captured by the European Space Agency's Gaia mission caught his eye. The pair of events brightened over a much longer timeframe than previously documented transients, but lacked some of their usual characteristics. 'Gaia doesn't tell you what a transient is, just that something changed in brightness,' Hinkle said. 'But when I saw these smooth, long-lived flares from the centers of distant galaxies, I knew we were looking at something unusual.' Hinkle soon reached out to observatory teams around the world for what would become a multiyear project to understand these anomalies. In the process, a third suspect was detected by the Zwicky Transient Facility at the Palomar Observatory in San Diego. After months of analysis, Hinkle and collaborators realized they were witnessing something unprecedented. The ENTs analyzed by astronomers displayed smoother, longer lasting flares that pointed towards something very particular—a supermassive black hole accreting a giant, wayward star. This contrasts with a more standard black hole that typically acquires its material and energy unpredictably, resulting in irregular brightness fluctuations. The energy and luminosity of an ENT boggles the mind. The most powerful ENT documented in Hinkle's study, Gaia18cdj, generated 25 times more energy than the most powerful known supernovae. For reference, a standard supernova puts out as much energy in a single year as the sun does across its entire 10 billion year lifespan. Gaia18cdj, meanwhile, manages to give off 100 suns' worth of energy over just 12 months. The implications of ENTs and their massive energy surges go far beyond their impressive energy outputs. Astronomers believe they contribute to some of the most pivotal events in the cosmos. 'These ENTs don't just mark the dramatic end of a massive star's life. They illuminate the processes responsible for growing the largest black holes in the universe,' said Hinkle. From here on Earth, ENTs can also help researchers as they continue studying massive, distant black holes. 'Because they're so bright, we can see them across vast cosmic distances—and in astronomy, looking far away means looking back in time,' explained study co-author and astronomer Benjamin Shappee. 'By observing these prolonged flares, we gain insights into black hole growth when the universe was half its current age… forming stars and feeding their supermassive black holes 10 times more vigorously than they do today.' There's a catch for astronomers, however. While supernovae are relatively well-documented, ENTs are estimated to occur at least 10 million times less often. This means that further study requires consistent monitoring of the cosmos backed by the support of international governments, astronomical associations, and the public.
