How stars die

A star is a standoff. Gravity pulls it inward, the heat of fusion in the middle pushes back out, and for almost all of a star’s life those two are equal. Fusion needs fuel, and the fuel runs out.

Everything turns on what can hold the core up

When the middle stops burning it starts falling, and what stops the fall settles the rest. In a star the weight of the Sun, the electrons refuse to be packed any closer, and that refusal alone holds up a cinder about as wide as the Earth, forever.

Above roughly eight Suns the core is too heavy for electrons, and it keeps falling until the neutrons take the load, which they do at about twelve kilometres across. Heavier again and neutrons do not hold either, and then there is nothing left in physics to stop it.

The heaviest stars of all never get that far. Their cores run so hot that light itself starts turning into matter, which drains the pressure holding the star up, and the collapse that follows lights the remaining fuel at once. The star comes apart completely and leaves nothing behind — no cinder, no neutron star, no hole.

The last day and the first ten million years

A heavy star burns hydrogen for ten million years, and carbon for three hundred, and neon for about five months. It burns silicon for two days. Almost all the energy of those late stages leaves as neutrinos, which pour straight out through the star without warming it, so each fuel goes faster than the one before. Nothing on the outside changes. Then the core falls three thousand kilometres in under a second.

What the visualisation does

Four stars, each stepped from long before the end through to whatever is left: the Sun, a supergiant twenty times its weight, a heavier one that collapses without exploding, and a first-generation giant that erases itself. Each is drawn cut open, and the frame holds still, so the sizes can be compared directly. Anything too small to draw is pointed at instead, with how much it has been magnified.