supernova
/ SOO-per-NOH-vuh /
A supernova is the death-explosion of a star — a single dying star that, for a few weeks, blazes about as bright as ten billion ordinary suns, briefly outshining its whole home galaxy. Imagine a city's worth of fireworks all detonating in one breathless instant, except the "city" is a ball of gas wider than our Solar System.
These explosions are among the universe's great foundries. The calcium in your bones, the iron in your blood, the oxygen you just breathed — almost every atom heavier than helium was cooked inside stars and then flung across space when those stars died: many in supernova explosions, others gently shed by quieter dying stars, and the very heaviest forged when stellar corpses collide. We are, quite literally, made of stardust scattered by ancient stars.
There are two main ways to make one, and a key number decides one of them. A massive star can run out of fuel and collapse under its own weight, rebounding in a titanic shock. Or a dense stellar ember called a white dwarf can siphon matter from a companion until it tips past the Chandrasekhar limit — about 1.4 times the Sun's mass — at which point it can no longer hold itself up and detonates. A common misconception: a supernova is not just a star "burning out." It is a violent, sudden explosion, not a quiet fading.
In 1054 CE, Chinese astronomers recorded a "guest star" so bright it was visible in daylight for 23 days — today we see its wreckage as the Crab Nebula.
A supernova witnessed and written down nearly a thousand years ago.
The name comes from Latin: nova means "new," because to ancient and early-modern stargazers a star seemed to appear out of nowhere. The prefix "super-" was added in the 1930s by Walter Baade and Fritz Zwicky to mark these as far mightier than ordinary novae. The Chandrasekhar limit is named for Subrahmanyan Chandrasekhar, who derived it in 1930 at age 19 on a voyage to England.