WHAT IS A PULSAR?
A pulsar is a rapidly rotating neutron star
that produces beams of electromagnetic
radiation from regions near its magnetic
poles.
As the neutron star rotates, these beams
can sweep across space like the beam of
a lighthouse.
If one of the beams points toward Earth,
astronomers can detect a repeating signal.
HOW IS A PULSAR FORMED?
Many pulsars are created when a massive
star reaches the end of its life and
undergoes a supernova explosion.
The star's core collapses under gravity,
compressing enormous amounts of matter
into an extremely dense neutron star.
Because the collapsing core becomes much
smaller, its rotation can become dramatically
faster.
WHY DOES IT PULSE?
The magnetic axis of a pulsar is often
misaligned with its rotation axis.
As the neutron star spins, its radiation
beams sweep through space.
From Earth, this can produce a regular
series of pulses.
The pulses are caused by the rotation of
the star rather than the star repeatedly
turning its radiation on and off.
EXTREME DENSITY
Neutron stars are among the densest known
objects in the Universe.
They can contain more mass than the Sun
compressed into a sphere only about
20 kilometres across.
A tiny amount of neutron-star material
would have an enormous mass on Earth.
KEY IDEAS
LIGHTHOUSE EFFECT
A pulsar's radiation beams sweep through
space as the star rotates, producing
regular pulses when viewed from Earth.
EXTREME ROTATION
Some pulsars rotate hundreds of times
per second, making them extraordinarily
precise cosmic clocks.
MAGNETIC FIELD
Pulsars possess extremely powerful
magnetic fields that help accelerate
particles and produce radiation.
MILLISECOND PULSARS
Some old pulsars rotate incredibly fast,
with periods of only a few milliseconds.
COSMIC CLOCKS
The highly regular timing of pulsars
allows astronomers to use them as
natural precision clocks.
PULSAR PLANETS
Astronomers have discovered planets
orbiting pulsars, showing that planets
can survive or form around stellar
remnants.
DID YOU KNOW?
Some pulsars are so precise that their
rotations can be measured with remarkable
accuracy — making them some of the most
reliable natural clocks known.
PULSARS AS PRECISION CLOCKS
Some pulsars rotate with extraordinary regularity, allowing astronomers to measure tiny changes in pulse arrival times. Pulsar timing can reveal orbital companions, test gravitational physics and probe matter under conditions impossible to reproduce on Earth.
Networks of precisely monitored millisecond pulsars can also be used to search for very low-frequency gravitational waves by looking for correlated timing shifts across many pulsars.
Magnetars · Supernovae