When a massive star runs out of fuel, its core collapses under the force of gravity, triggering a powerful and bright explosion that shatters the star’s outer layers. This explosive death is known as a supernova. However, what is seen in visible light accounts for only about 1% of the energy released, while the remaining energy is emitted in the form of neutrinos.
Neutrinos, also called ghost particles, are fundamental particles with very tiny mass, no electric charge, and very weak interactions with other matter, making them very difficult to detect. They can pass through stars, planets, galaxies, and even the human body undetected. Neutrinos can travel enormous distances without interacting, meaning they can carry direct information from the core of exploding stars. Hence, studying neutrinos can provide valuable information about core-collapse supernovae.
One remarkable thing is that the combined signal of many past core-collapse supernovae can be observed with increased detector sensitivity. The signal is known as the diffuse supernova neutrino background.
Super-Kamiokande is an enormous detector buried underground in Japan. This instrument can detect these particles through flashes created when a neutrino collides with protons or electrons in water molecules. These flashes are detected by the sensors in the detector.
Gadolinium has been added to this detector to improve its ability to detect neutrons produced in neutrino interactions. Scientists believe that this upgrade will help in the observation of supernova neutrinos across the universe. Another important question is what type of object is left behind after the explosion. The study of neutrinos can help scientists better understand these outcomes. Instead of observing a single supernova, the collective history of stellar explosions can be studied.