Imagine cramming everything our Sun is made of - a million Earths’ worth of matter - into a ball about 12 miles wide. That’s a neutron star. The Sun is squished down so hard that its atoms break, the electrons get crushed into the protons, and what’s left is a soup of pure neutrons packed as tight as it’s physically possible to pack matter.
The result is a substance so dense that a single sugar cube of it would weigh about a billion tons. If you teleported a teaspoon of neutron star material to Earth, it would punch through the planet’s crust and fall straight to the core.
Neutron stars also spin incredibly fast - some up to 700 times every second. Their surface gravity is around 2 billion times stronger than Earth’s, so anything that fell toward one would be stretched into a spaghetti-thin stream long before reaching the ground. They are the most extreme objects in the universe short of black holes.
