Neutron stars

Neutron stars are extreme remnants of a supernova explosion, where the core of a massive star collapses into a sphere only about 20 kilometers in diameter. Imagine compressing the mass of two of our Suns into a space the size of a small city; the density is so incredible that a teaspoon of this matter would weigh billions of tons. While in our solar system the Sun rotates slowly, these stars can spin up to 700 times per second. They are the densest objects in the universe that are not yet black holes, representing a fascinating frontier of physics where matter behaves very differently than what we are used to at home.