Neutron stars are the densest objects in space, cramming the mass of our Sun into a city-sized sphere!

A sugar-cube-sized piece would weigh a billion tons on Earth. These stellar remnants spin thousands of times per second, forming pulsars that beam radiation like cosmic lighthouses.

Some even collide, sending ripples through spacetime, gravitational waves! Einstein predicted them, and in 2015, we finally detected them. Mind-blowing, right?