A neutron star is the collapsed core of a massive star that has reached the end of its life. This means a neutron star is old, in the sense that it's the remnant of a star that has already gone through its main life cycle.

Here's why:

* Massive stars live fast and die young: Stars much larger than our Sun burn through their fuel quickly and have a relatively short lifespan.

* Supernova explosion: When a massive star runs out of fuel, it explodes in a supernova. The core collapses under its own gravity, forming a neutron star or, for the most massive stars, a black hole.

* Neutron stars are the remnants: The neutron star is the dense, collapsed core of the star left behind after the supernova.

So, while a neutron star is incredibly dense and energetic, it's not a "young" star, but rather the final product of a star that has already lived and died.