There are many different types of stars and all the stars are at many different stages of development. Their tells us a great deal about them. Ordinary small stars are red, larger ones are yellow and still larger ones are blue. Sometimes they seem to give off more light than they apparently should, and they grow into red, yellow and blue giants. Sometimes these grow even larger and may change colour and become supergiants, 10, 000 times as bright as the Sun. White dwarfs are caused by shrinking after their nuclear activity has ceased; in time they may become cold, black dwarfs. Supernovas are exploded stars which may condense to black holes or become neutron stars or pulsars.

When a massive star explodes as a supernova at the end of its life, its core collapses into a tiny and super dense object with not much more than our sun's mass. These small, incredibly dense cores of exploded stars are neutron stars. They are among the most bizarre objects in the universe.

A typical neutron star has about 1.4 times our sun's mass. They can range up to about two solar masses. Now consider that our sun has over 100 times Earth’s diameter. In a neutron star, all that mass is squeezed into a sphere that’s only about 12-25 miles (20-40 km) across, or about the size of an earthly city.

So perhaps you can see that neutron stars are very, very dense! A tablespoon of a neutron star material would weigh more than 1 billion U.S. tons (900 billion kg). That’s more than the weight of Mount Everest, Earth’s highest mountain.