Detecting the neutrinos from a supernova that’s about to explode

Neutrinos have a relationship with supernovae, massive stars that explode at the end of their lives. Neutrinos may have a role in triggering the eventual supernovae explosions of these stars. For that and many other reasons, astronomers are deeply curious about them.

A new study looked at what are called “pre-supernova neutrinos” which can be detected prior to the actual supernova. The new research should help astronomers understand the complex supernova phenomenon in greater detail.

The new study is titled “The sensitivity of presupernova neutrinos to stellar evolution models.” The study is co-authored by Ryosuke Hirai from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) at Monash University.

A dying star can emit an enormous amount of neutrinos, which may trigger the supernovae explosion itself. They flow through and out of the star before the explosion inside the star reaches the surface. Because of that, it’s possible to detect the neutrinos from a supernova before the star actually explodes.

That happened with SN1987A, a supernova that exploded in the Large Magellanic Cloud in 1987. About two or three hours before the light from that supernova reached us, three separate neutrino observatories detected a burst of neutrinos. Though the supernova released an enormous, astronomical number of neutrinos, the three observatories only detected a total of 25 of them, emphasizing how difficult studying neutrinos is.

That detection of neutrinos gave birth to neutrino astronomy. And the observations also aligned with theory showing that 99% of the energy from a supernova is in the form of neutrinos.

But 1987 was a long time ago, in terms of technological progress. Today’s neutrino detectors are better, and scientists think that if a similar supernova were to explode today, we’d detect many more neutrinos. Rather than the 25 detected in 1987, we would detect a whopping 50,000.

In fact the technology has improved so much, that astronomers think they’ll detect pre-supernova neutrinos days in advance of the explosion, rather than only two or three hours. Because we can now detect so many of them, and from an earlier stage of the supernova explosion, astronomers think they’ll be able to learn more about the supernova process when the next one occurs.

Even though astronomers and astrophysicists know a lot about the supernova process, there’s an enormous amount of detail still to be discovered, especially in the final phases. Researchers hope that by detecting a large number of neutrinos, and from earlier in the supernova process, they can straighten out some of the details. Lots of scientists have built models of a supernova’s final phases, but the outcomes are random and it’s hard to verify any theories.

Source: “Detecting the neutrinos from a supernova that’s about to explode” Universe Taday, 8 July 2020

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