What is a neutron star?
A neutron star is the extremely dense, collapsed core of a massive star that exploded as a supernova. It is about 20 kilometers wide but has more mass than the Sun.
When a star between about 8 and 20 to 25 times the mass of the Sun runs out of fuel, its core collapses under gravity. Protons and electrons are crushed together into neutrons, creating an object so dense that a teaspoon of its material would weigh about a billion tonnes on Earth.
Neutron stars spin very quickly and have powerful magnetic fields. Some send beams of radio waves from their magnetic poles. If a beam sweeps past Earth, we see regular pulses, like a lighthouse. These are called pulsars, and the fastest spin hundreds of times per second.
Collisions and gold
In 2017, scientists detected gravitational waves from two neutron stars colliding, and telescopes saw the explosion that followed. The collision produced heavy elements such as gold and platinum, suggesting that much of the universe's gold comes from such events.
Did You Know?
The first pulsar was discovered in 1967 by Jocelyn Bell Burnell, a graduate student at the University of Cambridge.