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Neutron stars and pulsars
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Ultra-dense remnants emitting periodic radio pulses.
After a supernova, a core of 1.4–2.2 M☉ collapses to a ball ~20 km across made of neutrons. A pulsar is a rapidly rotating magnetised neutron star emitting beams like a lighthouse, with pulses from ms to seconds.
Crab pulsar spins 30 times per second.
Magnetars have 10¹¹ T fields.
In more detail
Neutron stars are extremely dense remnants of massive stars, containing about 1.4 to 2 solar masses in a city-sized sphere. Rapidly spinning neutron stars are seen as pulsars.
Real-world uses
- Pulsars act as precise clocks for timing studies and gravitational wave detection.
- Neutron star mergers produce heavy elements.
- Radio astronomers use pulsars as natural clocks to test general relativity and to detect gravitational waves.
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Frequently asked questions
How dense is a neutron star?
Roughly the density of an atomic nucleus, several hundred million tonnes per cubic centimetre.
What is a pulsar?
A rapidly rotating neutron star whose beams sweep past Earth, producing regular pulses.
Why do pulsars pulse?
Their magnetic axis and rotation axis are misaligned, so a beam of radiation sweeps past Earth like a lighthouse.
Related topics in Particle Physics & Cosmology
Supernovae · White dwarfs · Chandrasekhar limit · Black holes in astrophysics · Galaxies · Milky Way