The heaviest stars only
How Does a Star Explode?
A giant star spends its life holding itself up. The moment it cannot, it falls in and rebounds.
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Step 1 of 5
Every star is a standoff.
Gravity is always trying to crush a star inward. The energy made in the core is always pushing outward. A star shining steadily is that argument staying level.
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Step 2 of 5
Heavy stars burn through their fuel fast.
The bigger the star, the harder gravity squeezes and the faster it has to burn to hold itself up. A giant star can use up in a few million years what the Sun takes billions to spend.
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Step 3 of 5
When the push stops, the fall is astonishingly quick.
The core cannot make any more energy, so gravity wins instantly. A core the size of Earth collapses to the size of a city in about a second.
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Step 4 of 5
The collapse rebounds, and the star is blown apart.
The core slams into itself, cannot compress further, and bounces. That rebound drives a shockwave outward through the rest of the star and tears it to pieces.
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Step 5 of 5
The wreckage becomes the next generation.
The explosion scatters everything the star made — including the heavier elements — back into space, where it joins the clouds that new stars and planets form from.
The iron in your blood was made inside a star that exploded before the Sun existed.
The short version
A heavy star explodes when its core can no longer push back against gravity: it collapses in about a second, rebounds, and blows the rest of the star into space.
Try it yourself
Look up the Crab Nebula. Chinese astronomers recorded that explosion in 1054, and the wreckage is still visibly flying outward.