Here's why:
* Massive Stars: Type II supernovae occur in stars that are at least 8 times the mass of our Sun.
* Nuclear Fusion: These stars fuse hydrogen into helium, then helium into heavier elements in their core. This process generates immense pressure that counteracts gravity.
* Core Collapse: As the star ages, it runs out of fuel for fusion in its core. The core, now mostly iron, can no longer support itself against gravity and collapses inward.
* Shockwave: The collapse of the core creates a shockwave that travels outwards through the star. This shockwave causes the outer layers of the star to explode.
In essence, the core collapse triggers the explosion that defines a Type II supernova.
