Neutron stars are the densest known objects in the universe. They are formed when the cores of massive stars collapse under their own gravity, compressing the protons and electrons into neutrons. Neutron stars have a density of about 10^17 grams per cubic centimeter, which is about 100 trillion times the density of water.

Here is a comparison of the density of neutron stars with other celestial objects:

- Neutron star: 10^17 grams per cubic centimeter

- White dwarf: 10^9 grams per cubic centimeter

- Earth: 5.51 grams per cubic centimeter

- Sun: 1.41 grams per cubic centimeter

- Jupiter: 1.33 grams per cubic centimeter

- Saturn: 0.69 grams per cubic centimeter

- Uranus: 1.29 grams per cubic centimeter

- Neptune: 1.64 grams per cubic centimeter

As you can see, neutron stars are far denser than any other celestial object. In fact, they are so dense that a single teaspoon of neutron star material would weigh as much as several billion tons.