A neutron star is a collapsed supernova--the collapse of a star after that last bright sunset. The star is made up entirely of neutrons, which are the neutrally charged part of an atom. These stars are very, very, very dense . To give you an idea:
A typical neutron star is about twice as massive as our sun. This mass is compressed into a ball about 12 km (7.4 miles) across. The sun, which is half as massive, is 720,000 km(444,000 miles) across.
It's as dense as if the entire world's population was standing on a sugar cube.
Neutron stars are very hot . The energy released during the collapse of the atomic structure of the molecules the star contains is enormous. The neutron star doesn't further collapse into a black hole, because of it's size. If the star's mass was 4 to 5 times that of the sun (instead of about twice the size of our sun), then even the Pauli principle, which states that no two neutrons, or any other fermionic particle, may occupy the same place at the same time, would no longer hold true, and the neutron star would become a black hole, further degenerating as the mass of the star collapsed into smaller and smaller perimeters, and in doing so became a more and more condensed mass, until it had infinite gravity, and zero volume.
How hot is "very hot "?
About 100,000,000,000 degrees kelvin. One hundred billion degrees kelvin converts as follows:
- 280 billion degrees Fahrenheit
- 173 billion degrees Celsius
"Billion" in the American usage: 1 billion equals 1,000 million. (Not the British usage where 1 billion equals a million million).
It is so hot, and soooo dense:
- one teaspoon of this material (which is the neutrons of iron atoms, we think) has a mass of 50,000,000,000,000 (50 billion) kilograms: 550 billion pounds, 275 million tons (American). One teaspoon is the weight of 300 automobiles.
- So hot, that this most dense material, much more dense than anything we know on Earth, much more dense than a typical iron atom, is molten liquid.