Watch the star die: a neutrino will help solve the supernova riddle

A recent research of 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. Researhc co-authored by scientist Ryosuke Hirai of the ARC Center for Advanced Discovery of Gravitational Waves (OzGrav) at Monash University studied stellar evolution models to verify uncertain predictions.

When a star dies, it emits a huge amount of neutrinos, which are believed to lead to a supernova explosion. Neutrinos flow freely through the star even before the explosion reaches the surface of the star. Last time, several dozen neutrinos were discovered from a supernova that exploded in 1987, a few hours before the explosion was noticed.

The next generation of neutrino detectors is expected to detect about 50,000 neutrinos from this type of supernova. The technology has become so powerful that scientists predict the detection of weak neutrino signals that occur a few days before the explosion. As a kind of supernova forecast, it will give astronomers the opportunity to catch the first light of a star.

It is also one of the few ways to directly extract information from the core of a star – similar to an X-ray image of your body. But the picture itself does not make sense if you do not know what you are looking at.

Although there is a common understanding of how a massive star evolves and explodes, scientists are still not sure about the threshold of a supernova explosion. Many physicists have tried to simulate its last phases, but the results seem random – there is no way to confirm whether they are true. Since the detection of neutrinos before the appearance of a supernova allows scientists to better evaluate these models, a group of scientists investigated the late stages of models of star evolution and their relationship with neutrino estimates before the supernova.

“This will help us make the most of information from future neutrino detections before the supernova. In this first study, we studied the uncertainty of one star, which is 15 times the mass of the sun. The neutrino emission calculated from these stellar models was very different in neutrino luminosity. The neutrino estimates before the supernova are very sensitive to these small details of the stellar model”.

Ryosuke Hirai of ARC Center of Excellence

The study revealed a significant uncertainty of neutrino predictions before the supernova, as well as the relationship between neutrino features and star properties.

The next supernova in our galaxy can happen any day, and scientists are eagerly awaiting the discovery of neutrinos before this event. But they still do not know what they can get in the end. This study outlines the first steps in interpreting data. In the end, researchers will be able to use neutrinos to understand the critical parts of the evolution of a massive star and the mechanism of a supernova explosion.