core-collapse supernova

When a massive star runs out of fuel, it does not fade — it detonates with a violence almost beyond comprehension, briefly outshining its entire host galaxy of a hundred billion stars. This is a core-collapse supernova, the catastrophic death of a star many times heavier than the Sun. In a few seconds it releases more energy than the Sun will radiate in its entire 10-billion-year life. It is the most powerful explosion an ordinary star can produce, and it forges and scatters many of the elements that make up worlds and living things.

The trigger is the failure of support. Once the star has built an iron core (the end of onion-shell burning), no further fusion can hold it up, and the core collapses in under a second, falling inward at a quarter the speed of light. It crashes down until the matter reaches the staggering density of an atomic nucleus, where it suddenly stiffens and rebounds. Almost all the gravitational energy released — a stupendous amount — pours out as a flood of ghostly particles called neutrinos. This neutrino burst, together with the rebound, blows the rest of the star apart, leaving behind a neutron star or, for the most massive stars, a black hole. The visible explosion is just a sliver of the total energy; 99 percent escapes as neutrinos.

These explosions come in observational types — II, Ib, and Ic — distinguished by whether the dying star still had its hydrogen and helium layers or had shed them first, but the underlying machinery is the same collapsing iron core. Core-collapse supernovae are essential to the universe: they manufacture and disperse oxygen, magnesium, silicon, and (in the chaos) some of the heaviest elements via the r-process, enriching galaxies so that later stars and planets can form. Roughly speaking, the oxygen you breathe was made and launched by stars that died this way.