When a giant star explodes, its core can collapse into a ball about 20 km across holding more mass than the Sun. Atoms are crushed together so tightly that a spoonful weighs as much as a mountain.
Truth label: Established. Strong evidence and broad agreement among experts.
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Spinning lighthouses
Some neutron stars, called pulsars, spin hundreds of times a second and sweep beams of radio waves across space.
Gold factories
When two neutron stars collide, they forge heavy elements, including much of the universe's gold.
Learn
- How they form. A star many times heavier than the Sun runs out of fuel, explodes as a supernova and leaves its crushed core behind.
Test yourself
Roughly how wide is a neutron star?
20 km. They are about the size of a city.
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