New research on ‘pre-supernova’ neutrinos.

A recent study of pre-supernova neutrinos, tiny cosmic particles that are extremely difficult to detect, has brought scientists one step closer to understanding what happens to stars before they explode and die. The study, co-authored by postdoctoral researcher Ryosuke Hirai of the ARC Center of Excellence for the Discovery of Gravitational Waves (OzGrav) at Monash University, investigated stellar evolution models to test uncertain predictions.

When a star dies, it emits a large number of neutrinos that are believed to drive the resulting supernova explosion. Neutrinos flow freely in and out of the star before the explosion reaches the star’s surface. Scientists can detect neutrinos before the supernova occurs; In fact, a few dozen neutrinos were detected from a supernova that exploded in 1987, several hours before the explosion came to light.

The next generation of neutrino detectors is expected to detect around 50,000 neutrinos from a similar type of supernova. The technology has become so powerful that scientists predict they will detect the faint neutrino signals that appear days before the explosion; As a kind of supernova forecast, it will give astronomers a warning to catch the first light of a supernova. It is also one of the only ways to extract information directly from the core of a star, similar to an X-ray image of its body, except that it is for stars. But an X-ray image doesn’t make sense unless you know what you’re looking at.

Although there is a general understanding of how a massive star evolves and explodes, scientists are still unsure about the period before the supernova explosion. Many physicists have attempted to model these final phases, but the results seem random; There is no way to confirm if they are correct. Since pre-supernova neutrino detections allow scientists to better evaluate these models, a team of OzGrav scientists investigated the later stages of stellar evolution models and their relevance to pre-supernova neutrino estimates.

OzGrav researcher and co-author Ryosuke Hirai says: “This will help us make the most of information from future pre-supernova neutrino detections. In this first study, we explored the uncertainty of a single star that is 15 times the mass of the sun. The neutrino emission calculated from these stellar models differed greatly in neutrino luminosity. This means that pre-supernova neutrino estimates are very sensitive to these little details of the stellar model. “

The study revealed the significant uncertainty of the pre-supernova neutrino predictions, as well as the relationship between the characteristics of the neutrino and the properties of the star.

“The next supernova in our galaxy may happen any day, and scientists hope to detect pre-supernova neutrinos, but we don’t yet know what we can learn from it. This study presents the first steps in how to interpret the data. Eventually, we may be able to use neutrinos. pre-supernova to understand crucial parts of the massive evolution of stars and the supernova explosion mechanism. ”