2023-08-31 19:08:23
Researchers have used supernovae to better understand elusive neutrinos, uncovering how their self-interactions might reshape our understanding of the universe.
A new study offers hope for a long-standing scientific problem.
In a groundbreaking study, researchers have taken an important step toward understanding how exploding stars can help reveal how neutrinos, mysterious subatomic particles, secretly interact with themselves.
Neutrinos, one of the least understood elementary particles, rarely interact with normal matter and pass through it invisibly, almost at the speed of light. These ghostly particles outnumber all the atoms in the universe and constantly and harmlessly pass through our bodies. Yet, due to their low mass and lack of electrical charge, they can be incredibly difficult to detect and study.
Discovering the mysteries of neutrinos with supernovae
Now, in a study published Aug. 15 in the journal Physical Review Letters, Ohio State University researchers set out a new framework detailing how supernovae — massive explosions heralding the death of collapsing stars — might be used as powerful tools to study how neutrino self-interactions can cause vast cosmological changes in the universe.
“Neutrinos only have very low rates of interaction with typical matter, so it is difficult to detect them and test their properties,” said Po-Wen Chang, lead author of the study and graduate student in physics at Ohio State. “That’s why we have to use astrophysics and cosmology to discover interesting phenomena regarding them. »
Considered to have played an important role in the formation of the early universe, neutrinos remain intriguing to scientists, even though they have learned that they originate from several sources, such as nuclear reactors or the interiors of dying stars. But by calculating how self-interactions would affect the neutrino signal from Supernova 1987A, the closest supernova observed in modern times, the researchers found that when neutrinos interact with themselves, they form a tightly coupled fluid. which expands under relativistic hydrodynamics – a branch of physics. which discusses how fluxes affect solid objects in two different ways.
Theories on neutrino outings
In the case of what is called a ““, researchers theorize that, just as the bursting of a highly pressurized balloon in the vacuum of space would push energy outward, an explosion produces a fluid neutrino moving in all directions. The second case, described as a “wind flow”, imagines a highly pressurized balloon with many nozzles, in which the neutrinos escape at a more constant rate, similar to a constant jet of wind.
Although the wind-flow theory is more likely to occur in nature, Chang said, if the burst event comes true, scientists might see new observable signatures of neutrinos emitted by supernovae, allowing a unprecedented sensitivity to neutrino self-interactions.
One of the reasons why it is so vital to understand these mechanisms is that if neutrinos act as a fluid, it means that they act together, as a collective. And if the properties of neutrinos are different as a collective than individually, then the physics of supernovae might experience changes as well. But it remains to be seen if these changes are due only to the break-up case or the exodus case.
Challenges and future prospects
“The dynamics of supernovae are complicated, but this result is promising because with relativistic hydrodynamics, we know there’s a fork in the road to understanding how they work now,” Chang said.
Still, more research needs to be done before scientists can rule out the possibility that the burst event also occurs inside supernovae.
However, despite the uncertainties, this research marks an important step in answering the decades-old astrophysical problem of how neutrinos scatter when ejected from a supernovae, said John Beacom, co-author of the study and professor of physics and astronomy at Ohio State. This study revealed that in the event of an explosion, unprecedented sensitivity to neutrino self-interactions is possible even with sparse neutrino data from SN 1987A and conservative analysis assumptions.
“This problem has remained virtually untouched for 35 years,” Beacom said. “So while we haven’t been able to fully resolve how neutrinos affect supernovae, what excites us is that we’ve been able to take a substantial step forward. »
In the future, the team hopes that their work will serve as a springboard for further investigation of neutrino self-interactions. Yet, since only two or three supernovae occur per century in the Milky Way, researchers are likely to have to wait decades more to collect enough new neutrino data to prove their ideas.
“We’re still praying for another galactic supernova to happen somewhere and soon, but the best we can do is try to build as much as possible on what we know before it happens,” he said. Chang said.
Other co-authors were Ivan Esteban, Todd Thompson, and Christopher M. Hirata, all from Ohio State. This work was supported by the National Science Foundation, NASA, and the David & Lucile Packard Foundation.
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