In 2024, the CHIME telescope caught over 700 fast radio bursts from a single neutron star in one hour. It was a hyperactive magnetar — a star with a magnetic field of 10¹⁵ gauss (a fridge magnet: about 100 gauss). The main secret of such power is a “sleeping volcano” inside.

If a neutron star is born with a mass greater than 2,1 solar, a quark core appears at its center — made of the particles that form protons and neutrons. As long as the star spins rapidly (period shorter than 5,5 milliseconds), this core stays calm. Rotation, like a hoop, holds it in check. But over time, stellar evolution leads to spin-down. When the period grows to a critical value, pressure drops, and the core explodes — a phase transition occurs, similar to water turning into ice, only here neutrons break down into free quarks. The quarks align in strict order and become a superpowerful permanent magnet. At that moment, a field of 10¹⁸ gauss is born inside.

This field breaks out to the surface, and a magnetar with a field of about 10¹⁵ gauss emerges. The eruption of an awakened volcano can explain many cosmic phenomena. If it happens inside a dense envelope, astronomers see a superluminous supernova. If the radiation punches through the debris, a fast radio burst is registered. The ejected matter, rich in neutrons, creates heavy elements through rapid neutron capture and produces a kilonova — a faint infrared glow. Sometimes a jet of particles is launched, and a gamma-ray burst is observed. Studying such events across different wavelengths is multi-messenger astronomy. Even earlier, Fritz Zwicky suggested that neutron stars are born in supernovae, and Jocelyn Bell Burnell discovered the first pulsars in 1967. Later, Subrahmanyan Chandrasekhar showed that stars have a mass limit beyond which they collapse. Now this same critical threshold — around 2,1 solar masses — determines whether the magnetic volcano inside a neutron star will wake. So giants that have slept for decades announce themselves with bright flares, and astronomers are getting ready to catch their awakening.