Cosmic Scale
Neutron star
Collapsed stellar core · Nearest ~400 light-years
How big is Neutron star?
Neutron star is about 22.0 km across.
See Neutron star in 3D, at true scale
When a star far heavier than the Sun runs out of fuel, its core collapses in about a second and the rest of the star explodes as a supernova. What is left is a neutron star: roughly one and a half times the mass of the Sun squeezed into a ball the size of a city, held up only by the pressure of neutrons packed shoulder to shoulder.
At a glance
| Diameter | 22.0 km |
|---|---|
| Mass | 2.78 × 10³⁰ kg |
| Diameter compared with Earth | 0.002 × Earth |
| Typical mass | 1.4 Suns |
| Density | ~10¹⁷ kg per m³ |
| Fastest spin | 716 turns a second |
| First found | 1967, as a pulsar |
Good to know
- A sugar cube of neutron-star material would weigh about as much as Mount Everest.
- Its surface gravity is around 200 billion times Earth's; falling one metre would take you to a tenth of the speed of light.
- Many sweep beams of radio waves around like lighthouses. We call those pulsars, and they keep time as well as atomic clocks.