A city-sized stellar object called a neutron star has a mass that is around 1.4 times that of the sun.
In fact, one teaspoon of material from these stars would weigh a billion tonnes.
Additionally, a neutron star's gravity is 2 billion times more powerful than Earth's.
How do neutron stars form?
When stars four to eight times as massive as the sun erupt in a cataclysmic supernova, neutron stars are created.
Image Credit:wikipedia
According to scientists from Space.com, "their outer layers can fly off in an often spectacular show, leaving behind a small, dense core that continues to collapse."
The name "neutron star" comes from the fact that protons and electrons combine to form neutrons when the material is compressed so tightly by gravity.
Because of their enormous gravitational pull, neutron stars are attracted to one another and eventually fuse.