As we know that a star is made of mostly hydrogen and helium atoms, 2 hydrogen atoms fusses and make up a helium atom and releases tremendous amount of heat, but star eventually ran out of fuel over a period of billions of years and
then there crust explode releasing enormous amount of energy and creating a supernova explosion and the core collapses which is mostly made up of neutrons which thus called a neutron star. This happens mostly when a star 10 to
20 times heavier than sun dies. If a star massive than this, then it becomes a black hole.
A neutron star is so heavy and has a gravitational force 2 billion times stronger than earth. Its gravitational force can distort the path of light. It is much similar to a black hole. A single cubic centimetre of neutron star weight around 400 million tonnes, or in simple words we can say that a spoonful of neutron star will weigh 1 to 6 billion tonnes. If you crush more than 10 million cars into a size of a sugar cube you can actually make a neutron star. And it rotates at an insane speed of 700 times per second.
The nearest neutron star from us is about 617 light years away nick named as ‘calvera’. If you want to go there with the most advanced spaceship ever build then it would take you around 17 million years.