What Is a Magnetar? The Universe's Most Magnetic Star
Magnetars are a rare type of neutron star with magnetic fields a trillion times stronger than Earth's — capable of releasing more energy in a fraction of a second than the Sun emits in 100,000 years. Recent research has finally captured one being born.
The Most Extreme Magnets in the Universe
If you compressed the Sun down to the size of a small city, you would get a neutron star. Take that neutron star and give it a magnetic field a thousand times more powerful than usual, and you have a magnetar — arguably the most extreme object in the known universe.
Magnetars are a rare subclass of neutron star whose magnetic fields reach between 1013 and 1015 gauss, roughly a trillion times stronger than Earth's magnetic field. For comparison, a hospital MRI machine generates about 30,000 gauss. A magnetar, at half the distance from Earth to the Moon, would erase every credit card on the planet and pull the iron out of your blood.
How a Magnetar Forms
Magnetars are born in the violent deaths of massive stars. When a star between 10 and 25 times the mass of the Sun exhausts its nuclear fuel, its core collapses in milliseconds, triggering a supernova explosion. What remains is a neutron star — an object roughly 20 kilometres across yet packing more mass than the Sun, so dense that a single teaspoon of its material would weigh over 100 million tonnes.
In about one in ten of these collapses, conditions are just right for an extraordinary amplification of magnetic energy. The collapsing core spins rapidly — hundreds of times per second — and the turbulent, electrically conducting fluid inside acts like a dynamo. According to a model developed in the 1990s by astrophysicists Robert Duncan and Christopher Thompson, this dynamo can convert rotational and thermal energy into magnetic energy, boosting the field to magnetar levels within the first seconds of the star's life, as NASA's Imagine the Universe explains.
The magnetic field is then sustained by persistent electrical currents flowing through a superconducting layer deep inside the neutron star.
What Magnetars Do
A magnetar's extreme field is not static — it shifts and evolves, and when it does, the consequences are spectacular.
- Starquakes: As the magnetic field rearranges, it stresses the solid outer crust. When the crust finally cracks, a starquake releases a burst of energy. In 2004, a magnetar called SGR 1806-20 produced a flare that, in just one-tenth of a second, released more energy than the Sun has emitted over the past 100,000 years, according to EarthSky.
- X-ray and gamma-ray bursts: The decay of the magnetic field continuously powers the emission of high-energy radiation. Magnetars are among the brightest X-ray sources in the sky.
- Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs): These are the two observational categories into which known magnetars fall, distinguished by their burst behaviour and persistent emission patterns.
Only about 30 confirmed magnetars are known in the Milky Way, according to the European Space Agency. Their active lives are brief: after roughly 10,000 years the magnetic field decays enough that bursting activity ceases.
A Magnetar Caught at Birth
For decades, astrophysicists suspected that magnetars power a class of exceptionally brilliant stellar explosions called superluminous supernovae — blasts up to 100 times brighter than ordinary supernovae. The theory held that a newborn magnetar spinning at hundreds of rotations per second acts like a cosmic engine, injecting enormous energy into the surrounding gas. But direct proof was elusive.
In March 2026, that changed. Astronomers announced in the journal Nature that they had detected a distinctive "chirp" — a brightness oscillation whose frequency steadily increases — inside a superluminous supernova that exploded about one billion light-years away. As Science News reported, the chirp pattern is explained by a rapidly spinning magnetar inside the blast whose precessing disk of ejected material wobbles faster and faster as the system evolves — a relativistic effect known as Lense-Thirring precession, predicted by Einstein's general relativity.
The finding, supported by research from UC Berkeley and UC Santa Barbara, represents the first time astronomers have effectively witnessed a magnetar's birth and confirmed its role in driving one of the universe's most luminous events, according to Berkeley News.
Why Magnetars Matter
Beyond their intrinsic drama, magnetars are laboratories for physics impossible to replicate on Earth. Their interiors contain matter at densities that test the limits of quantum chromodynamics — the theory governing how quarks and gluons interact. The behaviour of superconducting and superfluid components deep inside a neutron star remains an active area of theoretical physics.
Magnetars have also been proposed as a possible source of Fast Radio Bursts (FRBs) — millisecond flashes of radio waves detected from across the cosmos. In 2020, a magnetar in our own galaxy produced an FRB-like event, strengthening that connection.
As gravitational-wave detectors grow more sensitive and X-ray observatories map the sky in greater detail, magnetars will remain among the most productive objects in astrophysics — extreme enough to challenge our best theories, and close enough to the edge of physics that studying them pushes the boundaries of what we know about matter, energy, and spacetime itself.
