Astronomers recently observed a massive star in the Andromeda Galaxy (M31) that bypassed the usual supernova explosion and collapsed directly into a black hole. Typically, stars around eight times the Sun’s mass end their lives with a supernova, an intense explosion that can briefly outshine entire galaxies and leaves behind either a black hole or neutron star. This new discovery, led by Kishalay De from MIT, provides insight into a rare alternative process: failed supernovae.

The star, named M31-2014-DS1, had an initial mass of around 20 solar masses. When it reached the end of its life, its hydrogen supply diminished, causing the star to lose the outward pressure needed to counterbalance its own gravity. The resulting core collapse usually triggers a supernova. However, M31-2014-DS1 experienced a unique kind of failure in this process. Instead of an explosion, the star gradually dimmed, fading significantly from 2016 to 2019, until it was undetectable in recent observations. This “failed supernova” is attributed to the star’s neutrino shock—an intense burst of neutrinos created during the collapse, which should ideally power a shock wave strong enough to expel the outer layers. For M31-2014-DS1, this shock wave stalled, and the star imploded, forming a black hole with about 6.5 solar masses.

Failed supernovae are notoriously difficult to observe since they are marked by the absence of a visible explosion. The only other confirmed example is N6946-BH1 in the “Fireworks Galaxy” (NGC 6946), discovered in 2009. A broader survey has suggested that up to 20–30% of massive stars might end their lives in this way, offering a fascinating glimpse into the diversity of stellar deaths and the formation of black holes.