Science
What is A neutron star?
A neutron star is the ultra-dense, collapsed core left behind when a massive star explodes as a supernova. Gravity crushes its protons and electrons together into neutrons, packing more than the Sun's mass into a city-sized sphere.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains a neutron star.
Key things to understand
- 1Forms when a giant star runs out of fuel and its core collapses.
- 2So dense that a teaspoon of it would weigh billions of tons.
- 3Only about 20 km across, yet heavier than the entire Sun.
- 4Often spins rapidly, beaming radiation as a 'pulsar.'
- 5Its surface gravity is second only to a black hole's.
Frequently asked questions
- How dense is a neutron star?
- Extraordinarily — a sugar-cube-sized piece would weigh about as much as all of humanity combined.
- What is a pulsar?
- A fast-spinning neutron star whose beams of radiation sweep past Earth like a lighthouse, producing regular pulses.
- What happens if a neutron star gets heavier?
- Above a mass limit, gravity overwhelms even neutron pressure and it collapses further into a black hole.