On February 23, 1987, a massive blue supergiant star known as Sanduleak -69 202, located in the Large Magellanic Cloud—a satellite galaxy of the Milky Way—exploded in a brilliant supernova, designated SN 1987A. This event was the closest supernova observed since the invention of the telescope and the first one from which scientists were able to detect neutrinos, subatomic particles that are notoriously difficult to observe. Three underground neutrino detectors—Kamiokande-II in Japan, IMB in Ohio, and Baksan in the Caucasus—recorded a total of 24 neutrinos in just a few seconds. These particles arrived about two hours before the first visible light from the explosion was observed on Earth. The neutrinos were emitted almost instantly from the collapsing core of the star, while visible light took longer to escape, having to pass through the outer layers of the star. This confirmed a key theory that the majority of a massive star's energy during a supernova is released in the form of neutrinos, not light. Scientists estimate that the explosion emitted around 10^58 neutrinos, accounting for about 99 percent of the total energy released in the event. For over 37 years, the neutron star formed by the explosion remained hidden behind a shroud of dust and gas. However, in February 2024, the James Webb Space Telescope finally detected the neutron star, confirming its existence and solving a long-standing mystery. The discovery, published in the journal Science, was described by Mike Barlow from University College London as a significant breakthrough, ending a decades-long uncertainty about whether a neutron star existed in the remnants of SN 1987A. An international alert system known as SNEWS, established in 1998, has been monitoring for a new nearby supernova for over 25 years. This system was created during a workshop that brought together neutrino physicists, supernova theorists, and astronomers, aiming to detect early neutrino signals from a galactic supernova. Since 2005, SNEWS has operated automatically, linking experiments like Super-Kamiokande, IceCube, and Borexino. Despite its long period of vigilance, no actual supernova alert has been triggered in nearly three decades. SN 1987A was the first supernova visible to the naked eye since the one observed by astronomer Johannes Kepler in 1604. Without the underground neutrino detectors that shielded them from cosmic noise, scientists would not have been able to detect the invisible neutrino signal from the explosion. Such events are rare, with core-collapse supernovae in the Milky Way estimated to occur about 1.63 times per century, though this number has a margin of uncertainty.