Astronomers find strongest case yet for a star-annihilating pair-instability supernova

SN 2023vbw, spotted by the Zwicky Transient Facility in October 2023 in a metal-poor dwarf galaxy 1.3 billion light-years away, was initially filed as an ordinary Type II supernova. A new analysis posted to arXiv argues it is something far rarer: a pair-instability supernova, an explosion violent enough to obliterate the entire star and leave no neutron star or black hole behind. The event’s light curve broke the Type II mold — climbing steadily to peak brightness around day 190, dropping sharply by day 230, and radiating roughly 3×10^50 ergs, more than ten times a normal Type II. Its near-constant temperature during the rise implies a sustained internal heat source, and late-stage hydrogen emission lines point to ejecta slamming into a disk-like shell the star shed before dying.

Modeling suggests the progenitor was a blue supergiant resembling SN 1987A’s, but vastly larger: ejecta mass between 170 and 350 solar masses, with kinetic energy 60 to 130 times the ceiling for an iron core-collapse supernova. The host galaxy’s metallicity — about a tenth of the sun’s — matches theoretical conditions for pair instability, in which extreme core temperatures spawn electron-positron pairs, sapping the radiation pressure that holds the star up and triggering a runaway thermonuclear blast. The authors propose the star may have formed from a binary merger, which would explain the circumstellar disk, though they concede open questions about whether such stars die as red or blue supergiants and when a merger would occur.

The explosion remains bright enough for follow-up observations of its mass-loss history and nucleosynthesis. More consequentially, the Vera Rubin Observatory and Nancy Grace Roman Space Telescope are expected to catch tens to hundreds of similar events, opening a systematic window onto how the universe’s most massive stars live and die.