Glossary · Thiên văn học
Neutron star
The extremely dense core left behind when a massive star runs out of fuel and its core collapses, usually in a supernova explosion. During the collapse, protons and electrons are crushed together into neutrons. A neutron star is only about the size of a city.
When a massive star runs out of fuel, its core collapses and protons and electrons are crushed together into neutrons. According to NASA, if the collapsing core is between about 1 and 3 solar masses, the newly formed neutrons can halt the collapse, leaving a neutron star. If the original star is more massive still, the collapse does not stop and a black hole forms.
A neutron star is about 20 km across. Its matter is so dense that, according to NASA, a sugar-cube-sized piece would weigh about a billion tons on Earth.
Many neutron stars are observed as pulsars: rotating neutron stars that send out powerful beams of radiation along their magnetic poles. When a beam sweeps across Earth, we receive pulses of radiation at very regular intervals.