How Many Neutrinos Are Released In a Supernova

Kamiokande began to attract public attention after an incident in 1987. At this time, as luck would have it, a gift arrived from the universe. These are 11 neutrinos produced by a supernova explosion.

Kamiokande, which began observing in 1983, was hoping that at least one of the huge number of protons contained in 3,000 tons of pure water would disintegrate. Of course, they were also detecting neutrinos coming from the sun, but many physicists seemed to have high hopes for the observation of the proton decay phenomenon predicted by the Grand Unified Theory of Elementary Particles.

In 1987, a supernova explosion was observed in the Large Magellanic Cloud. When a supernova explosion is viewed from Earth, stars that suddenly become brighter appear in the sky, and many of them disappear within a few days. Bright objects can be seen even during the day. The Large Magellanic Cloud is about 160,000 light-years from Earth, so this supernova explosion is a past phenomenon that occurred about 160,000 years ago.

At that time, neutrinos flew into Kamiokande. According to observational data at the time, 11 neutrinos were detected for 13 seconds starting at 16:35:35 on February 23, 1987. It must have come from the Large Magellanic Cloud, where a supernova exploded. The observation period coincides exactly.

Detecting neutrinos is extremely difficult as they have little interaction with matter. The 11 neutrinos detected by Kamiokande means that a huge number of neutrinos fell on Earth in a short period of time. Of course, the total number of neutrinos generated at the site of the supernova explosion, approximately 160,000 light years away, is immeasurable.

At the time, it was known from astrophysical theory that large numbers of neutrinos would be produced during a supernova explosion. This is because it was believed that dynamic astronomical phenomena such as supernova explosions could be explained by the terminal reactions of atomic nuclei. Observations of neutrinos at Kamiokande provided clues to distant celestial phenomena. It is truly a gift from the universe.