1. Introduction
Pulsars are among the most extreme objects in the universe: rapidly rotating neutron stars whose radio emission beams sweep space like a cosmic lighthouse. Discovered in 1967 by Jocelyn Bell Burnell, they were initially nicknamed LGM-1 (Little Green Men) because their regularity seemed artificial.
2. Neutron stars
A neutron star is the remnant of a supernova: when a massive star exhausts its nuclear fuel, its core collapses under its own gravity. Protons and electrons combine to form neutrons. The result is an object of about 1.4 solar masses compressed into a sphere 10–20 km in diameter.
The density is staggering: a teaspoon of neutron star matter would weigh about one billion tons. Conservation of angular momentum during collapse considerably accelerates rotation — like a skater pulling in their arms.
3. Rotation and beams
Pulsars rotate at speeds ranging from a few turns per second to more than 700 turns per second for millisecond pulsars. Their rotation axis and magnetic axis generally do not coincide. Radio emission beams are emitted along the magnetic axis.
When the magnetic axis points toward Earth during rotation, we detect a radio pulse. This is the lighthouse mechanism: rotation produces regular pulses, not a single geometric spiral.
4. The magnetosphere
The magnetosphere of a pulsar is a region of co-rotating charged plasma. The co-rotation limit — the light cylinder — is the distance at which the co-rotation speed would reach the speed of light. Beyond this limit, charged particles can no longer co-rotate and are ejected, carrying away angular momentum and gradually slowing the pulsar.
5. Magnetars
Magnetars are neutron stars with extraordinarily intense magnetic fields — up to 10¹⁵ gauss, a billion times Earth's magnetic field. These extreme fields can deform the structure of local spacetime and produce gamma-ray bursts of colossal energy.
In 2004, a magnetar located 50,000 light-years away emitted a burst so intense that it partially ionized Earth's upper atmosphere — from the other side of the galaxy.
6. Conclusion
Pulsars illustrate how rotation — a motion fundamentally linked to the spiral — can produce phenomena of extraordinary regularity and power. The physics of rotation, intense magnetic fields and the gradual spin-down of these extreme objects reveals the laws of physics in regimes inaccessible to terrestrial laboratories.