Here’s a riddle: What’s as big as a golf ball but weighs as much as a mountain? The answer: a neutron star. Actually, neutron star material, to be exact.
It may sound impossible for this hypothetical golf ball to exist; a golf ball that would crumple your driver if you swung at it, and crush the tee that it was placed on. It would probably even drill itself deep into the ground it was placed on. But matter this heavy actually exists in the physical world. It exists in neutron stars, and neutron stars exist in relative abundance.
It’s estimated that there exist around 1 billion neutron stars in our galaxy. These stars have masses that are around 1.3-2.5 times the mass of our own sun. That might not seem impressive, but while the radius of the sun is about 109 times the radius of the earth, a neutron star could fit within an area about the size of Manhattan Island. This creates material so dense that a single teaspoon of neutron star would weigh over 1 billion tons, which is about the weight of Mount Everest.
These hefty little stars are the remnants of supernovas: the giant explosion created by the death of a star. When a star gets too heavy to support itself it collapses onto its core. This extreme pressure is so strong that the atoms in the core have their protons and electrons forced together to make neutrons. The outer matter of the star then bounces off of the core and blows up into outer space, leaving behind a dense “little” neutron star.
The gravitational forces created by neutron stars are extremely intense. It’s hypothesized that there can exist “mountains” on neutron stars that can be as tall as 5 millimeters. They’re so short due to the insane amounts of gravitational pressure holding them down. These mountains are a breeze to climb on Earth, but good luck doing it on a neutron star. Before you can even think about climbing one of these mountains, gravity will spread you out into a miles-wide atomically-thin goop. My advice? Don’t go hiking on a neutron star.