The year 1987 could not have started much better for the physics community. Condensed-matter researchers were buzzing over the discovery of cuprate superconductors. Particle physicists were celebrating President Reagan’s endorsement of building the ill-fated Superconducting Super Collider. And then a star exploded on the scene: Supernova 1987A, the light and neutrinos of which reached Earth 30 years ago today.
Astronomer David Helfand captured all the excitement in an August 1987 Physics Today article. By that writing, the explosion in the Large Magellanic Cloud had already allowed theorists to confirm some supernova predictions and shatter others. Careful examination of archival telescope plates had revealed that the progenitor star, Sanduleak –69° 202, was much beefier than the Sun, as expected; but its blue color (B3I, for the stellar taxonomists out there) defied predictions that red supergiants were the victims of such explosions.
The light of SN 1987A may have caught the attention of sky watchers, but it was the invisible component of the explosion that established a new field: neutrino astronomy. The Kamiokande II detector in Japan, an experiment designed to hunt for the decay of protons, clocked 11 neutrino events on 23 February. The neutrino detection came at 7:35 Universal Time, some three hours before the first visual evidence of SN 1987A. Another proton decay experiment, at the Irvine-Michigan-Brookhaven detector in Ohio, tracked eight events at the same time.
Despite power outages at both sites that affected data collection and analysis, the evidence was clear that scientists had achieved the first detection of extrasolar neutrinos. More importantly, the detections confirmed theoretical predictions that the vast majority of a supernova’s energy is radiated away by neutrinos, which pass nearly unimpeded through the dense stellar core and get a head start on electromagnetic radiation. The data also allowed particle physicists to set upper limits for neutrino mass.
Three decades later, neutrino astronomy is coming into its own. In 2013 the IceCube experiment in Antarctica detected the first definitively astrophysical neutrinos that were not tied to SN 1987A. Astrophysicists hope to correlate data collected by conventional telescopes with those from neutrino and cosmic-ray detectors to learn more about the universe’s most energetic phenomena, including supernovae.
Although the mechanism for type II supernovae has not been totally deciphered (theorists still have trouble getting their simulated collapsing stars to go kablooey), researchers have more predictive power than they did 30 years ago. On the observational side, the All-Sky Automated Survey for Supernovae and similar projects continuously pore through telescope images looking for transient objects that might signal the detonation of a massive star.
And then there are the remains of SN 1987A, which are a favorite target of the Hubble Space Telescope. Questions about the explosion’s aftermath include one dense, Manhattan-sized mystery: Somewhere within the remnant, physicists surmise, sits the neutron star that littered our planet with light and neutrinos exactly three decades ago.