Pulsars are rapidly rotating neutron stars that emit beams of electromagnetic radiation. When one of those beams sweeps across Earth, astronomers observe regular pulses, rather like a lighthouse beam.
Pulsars are extreme objects. They can pack more mass than the Sun into a sphere roughly the size of a city, rotate many times per second and carry very strong magnetic fields.
Formation
Most pulsars are formed after a massive star explodes as a supernova. The outer layers are thrown into space while the core collapses into a neutron star.
If the neutron star rotates and its magnetic poles emit beams of radiation, those beams may be detectable as pulses when they cross an observer's line of sight.
Discovery
The first pulsar was discovered in 1967 by Jocelyn Bell Burnell and Antony Hewish at the University of Cambridge. The signal was so regular that it was initially nicknamed LGM-1, short for "Little Green Men", before a natural explanation was established.
The discovery became one of the most important moments in radio astronomy because it confirmed a new class of compact stellar remnant.
Characteristics
Pulsars are known for:
- Rapid rotation.
- Strong magnetic fields.
- Highly regular pulses.
- Emission across parts of the electromagnetic spectrum.
- Gradual slowing over time as rotational energy is lost.
Some pulsars rotate in milliseconds. These millisecond pulsars are especially useful as precise natural clocks.
Types
Radio Pulsars
Radio pulsars are detected mainly through radio pulses. Many classic pulsar discoveries came from radio astronomy.
X-ray and Gamma-ray Pulsars
Some pulsars are observed at higher energies, including X-rays and gamma rays. Space telescopes are important for studying these objects because Earth's atmosphere blocks much high-energy radiation.
Millisecond Pulsars
Millisecond pulsars rotate extremely quickly. Many are thought to have been spun up by accreting matter from a companion star.
Pulsar Wind Nebulae
A pulsar can energise surrounding particles, producing a pulsar wind nebula. The Crab Nebula is a famous example linked to a young neutron star.
Scientific Use
Pulsars are useful because their timing can be extremely stable. They are used to study dense matter, stellar evolution, magnetic fields, supernova remnants, binary systems and gravity.
Networks of precisely timed pulsars can also be used in pulsar timing arrays, which search for very low-frequency gravitational waves.
See Also
References
Discussion log
Use comments for sourcing notes, corrections, and disputed details.
No comments yet.