The shortest stage in a star's life cycle is the supernova explosion.

Here's why:

* Supernovae are incredibly powerful events that occur over a very short period of time, typically lasting only a few weeks or even days.

* In contrast, the other stages of a star's life, like the main sequence phase (where a star fuses hydrogen into helium), can last for billions of years.

So, while a supernova is the most dramatic and explosive event, it's also the most fleeting part of a star's life.