Neutron Stars Are Unbelievably Dense
Though most neutron stars could fit inside a large city, they have two to three times the mass of our sun. They're called neutron stars because the pressure in their core causes their protons and electrons to merge into neutrons. Their magnetic fields are millions of times stronger than that of Earth, and neutron stars with highly powerful magnetic fields are called magnetars. Those that emit a beam of electromagnetic radiation are known as pulsars.
from Chandra X-ray Observatory
Key Facts In This Video
Neutron stars form when a star runs out of fuel and collapses. (1:12)
The fastest-spinning neutron star rotates more than 700 times per second. (1:55)
The magnetic fields of magnetars are so strong that they can break apart the crust and cause a "starquake." (3:03)