Why do massive stars die?

1 Answer

-Stars die because they run out of nuclear fuel.
-Massive stars use up their fuel quicker
-Smaller stars like red dwarfs will last longer


  • You can skip to the dots (•••) near the bottom if you want to get straight to the point

Let's go through the life of stars...
(I'll try not to go off topic)

*Some notes before we start:
The word, 'Massive' in astronomy is regarding the total mass of the subject. So when it is said that a star is Massive, it's not referring to size, but to the mass of it. Although mass and size correlate to some degree.

Every star fuses hydrogen into helium in its core when it is first born. Stars similar to our sun, stars that get to be around the size of Jupiter called Red Dwarfs and Supermassive stars that are usually hundreds of times more massive than our sun all undergo this first stage of the nuclear reaction.

The more massive a star is, the higher temperature its core reaches and the faster it burns through its nuclear fuel.
As a star's supply of hydrogen to fuse runs out, it begins to contract and the temperature increases. If the star gets dense and hot enough, it will start to fuse heavier elements.

Sun-like stars, once hydrogen burning completes, will get hot and dense enough to fuse helium into carbon, but that's the most that star this(sun) size will get to accomplish. To enter the next stage of the nuclear reaction, a star eight or more times more massive than our sun is required.

Now we're getting into Carbon Fusion
Sun-like stars would expel their outer layers as a planetary nebula and contract into a white dwarf. And the Red dwarfs that never even make it to burning helium would contract down to a white dwarf as well.
But the more massive stars give a cataclysmic show...


Often, especially in the lower-mass end of the spectrum (~20 solar masses and under), the core temperature steadily rises and fusion goes onto heavier elements: Burning carbon to oxygen and/or neon, and then even burning magnesium, silicon, and sulfur, which reaches a climax in a core of iron, cobalt, and nickel.

Since fusing these elements would use more energy than it produces, the core implodes and collapses into a supernova form. After the supernova, one of two permanent outcomes occur. Either the newly dead supermassive star becomes a neutron star, it becomes a black hole.