Astronomers Witness Formation of Magnetar for First Time

One billion light-years from Earth, a star 25 times the mass of our Sun died in spectacular fashion. In its final moments, it did not merely explode — it screamed. And for the first time in the history of astronomy, scientists heard the cry and decoded its meaning: the birth of a magnetar, one of the most extreme objects in the known universe.

The discovery, published in Nature on March 11, 2026, resolves a debate that has simmered in astrophysics for over a decade and a half [3]. It confirms that magnetars — neutron stars with magnetic fields so powerful they could erase a credit card from halfway across the solar system — are the engines driving the universe's brightest stellar explosions. And the clinching evidence came not from any exotic new detector, but from an elegant signature hidden in plain sight: a "chirp" in the dying light of a supernova, explained by nothing less than Einstein's general theory of relativity.

The Supernova That Refused to Fade Quietly

In December 2024, the ATLAS survey telescope flagged a new point of light in the sky. Designated SN 2024afav, the event was quickly identified as a superluminous supernova — a class of stellar explosion that shines at least 10 to 100 times brighter than an ordinary supernova [1]. These ultra-bright blasts are exceedingly rare, with roughly 262 catalogued through the end of 2022, and their power source has been one of astrophysics' most contested questions.

Joseph Farah, a fifth-year graduate student at UC Santa Barbara working with the supernova group at Las Cumbres Observatory (LCO), began tracking SN 2024afav almost immediately. Using LCO's global network of 27 telescopes spanning six continents, Farah and his collaborators monitored the supernova continuously for over 200 days — an unusually sustained and high-cadence observing campaign [2][6].

What they saw was unlike anything previously recorded. After SN 2024afav reached peak brightness around 50 days post-explosion, it did not simply fade. Instead, its luminosity oscillated downward in a series of four distinct bumps, each one arriving more quickly than the last [1]. Previous superluminous supernovae had occasionally shown one or two such undulations. Four bumps, with a clear pattern of accelerating frequency, had never been seen.

"There was just no existing model that could explain a pattern of bumps that get faster in time," Farah said [2].

He had discovered a chirp — a signal whose frequency increases over time, reminiscent of the gravitational wave chirps detected from merging black holes. But this chirp was written in light, not spacetime ripples, and it demanded a new explanation.

Inside the Machine: What Powers a Superluminous Supernova

To understand why the chirp mattered so much, it helps to understand the mystery it solved.

When a massive star exhausts its nuclear fuel, its core collapses under gravity in a fraction of a second. The outer layers are blasted outward in a supernova. What remains at the center is either a black hole or a neutron star — a ball of matter so dense that a teaspoon would weigh roughly a billion tons, crushed into a sphere just 10 miles across.

Ordinary supernovae are powered primarily by the energy of this collapse and the radioactive decay of nickel-56 produced in the explosion. But superluminous supernovae are far too bright to be explained by these mechanisms alone. Something else must be injecting enormous amounts of energy into the expanding debris.

Two leading hypotheses emerged. One proposed that the supernova shock wave slams into a dense shell of gas previously expelled by the dying star, converting kinetic energy into light. The other, proposed in 2010 by UC Berkeley physicist Daniel Kasen and UC Santa Barbara's Lars Bildsten, argued that a rapidly spinning, highly magnetized neutron star — a magnetar — could act as a central engine, its spinning magnetic field accelerating charged particles that collide with the supernova debris and dramatically amplify its brightness [1][7].

"A magnetar can act as a powerful engine that lights up the supernova to extraordinary brightness," Kasen explained [4].

For 16 years, the magnetar model remained a compelling but unproven hypothesis. There was circumstantial evidence — the light curves of many superluminous supernovae could be fit with magnetar models — but no direct, unambiguous signature that a magnetar was present. Until SN 2024afav.

Decoding the Chirp: Einstein Meets Exploding Stars

Farah's breakthrough came when he realized the chirp could be explained by a specific prediction of general relativity called Lense-Thirring precession, also known as frame-dragging [2][3].

Here is the physical picture: When the massive star collapsed to form the magnetar, not all of the stellar material escaped in the explosion. Some fell back toward the newborn neutron star, forming an accretion disk — a swirling ring of matter spiraling inward under gravity. Crucially, this disk was not aligned with the magnetar's spin axis. It was tilted.

General relativity predicts that a spinning mass drags the fabric of spacetime around with it. For a magnetar spinning over 1,000 times per second, this effect is enormous. The twisted spacetime forces the tilted accretion disk to wobble — to precess — like a gyroscope that is not perfectly upright. As the disk precesses, it periodically blocks and redirects radiation from the magnetar, creating rhythmic fluctuations in the supernova's brightness [5].

The key insight was that as the accretion disk gradually spirals inward toward the magnetar, it precesses faster. The wobble accelerates. The brightness fluctuations come at shorter and shorter intervals — producing exactly the chirp that Farah observed.

Working with theorist Logan Prust of the Flatiron Institute, Farah tested every alternative explanation. Purely Newtonian effects could not reproduce the timing. Precession driven by the magnetar's magnetic field did not match either. "We tested several ideas, including purely Newtonian effects and precession driven by the magnetar's magnetic fields, but only Lense-Thirring precession matched the timing perfectly," Farah said [2][5]. "It is the first time general relativity has been invoked to describe the mechanics of a supernova."

Source: Schematic based on Farah et al. 2026, Nature

Data as of Mar 11, 2026CSV

Portrait of a Newborn Magnetar

From the chirp signal, the team extracted remarkably precise measurements of the magnetar's properties. The newborn object has a spin period of approximately 4.2 milliseconds — meaning it completes roughly 238 rotations every second [1]. Its magnetic field is estimated at approximately 300 trillion times the strength of Earth's magnetic field, placing it squarely in magnetar territory [1].

To appreciate these numbers requires some cosmic perspective. Earth's magnetic field, which deflects solar wind and allows compasses to function, measures about 0.5 gauss at the surface. The strongest continuous magnetic fields produced in human laboratories reach about 450,000 gauss. A typical neutron star, already the densest form of matter that isn't a black hole, generates fields of around 10 trillion gauss.

A magnetar's field reaches 100 trillion to 1 quadrillion gauss — strong enough to distort the electron orbits of atoms, stretching them into elongated cigars aligned with the field lines. At a distance of 600 miles from a magnetar, the magnetic field would be intense enough to disrupt the molecular bonds holding together the atoms in a human body [9]. These are, by a staggering margin, the most powerful magnets in the known universe.

Only about 29 magnetars have been identified in the Milky Way, though models suggest as many as 30 million inactive ones may lurk unseen throughout the galaxy, their magnetic fields having decayed below detectable thresholds over roughly 10,000 years [9].

Why This Discovery Matters

The confirmation that magnetars power superluminous supernovae is significant on multiple fronts.

Resolving a 16-year debate. The Kasen-Bildsten magnetar model, first proposed in 2010, has now been elevated from a leading hypothesis to an observationally verified mechanism. The chirp provides a direct, physical signature — not merely a curve-fitting exercise — that ties the supernova's behavior to a specific central engine [7].

A new laboratory for general relativity. Lense-Thirring precession has been measured before in much milder gravitational environments — most notably by NASA's Gravity Probe B satellite, which detected frame-dragging effects from Earth's rotation. But detecting it in the extreme gravitational field of a magnetar represents a qualitative leap. "Everything about the system is extreme," said Adam Ingram, an astrophysicist at Newcastle University who was not involved in the study. "The gravitational field is strong enough for the most exotic predictions of general relativity to be large effects" [4].

A new class of observable phenomenon. The chirping supernova is not merely a one-off curiosity. Farah's model predicts that the chirp should be a generic feature of superluminous supernovae powered by magnetars. Armed with the model, astronomers can now search archival data for similar signals that may have been overlooked, and design future observing campaigns to catch them in real time.

Constraining magnetar physics. Because the chirp encodes information about the magnetar's spin rate, magnetic field strength, and the geometry of the accretion disk, each new detection will provide independent measurements of these quantities — building up a statistical picture of how magnetars are born and what conditions produce them.

The Road Ahead: Rubin and the Coming Deluge

The timing of this discovery is fortuitous. The Vera C. Rubin Observatory in Chile — the most ambitious optical survey telescope ever built — began issuing its first science alerts in February 2026, sending out 800,000 alerts in a single night flagging new asteroids, supernovae, and other transient phenomena [2]. Over its planned 10-year Legacy Survey of Space and Time (LSST), Rubin will produce 10 terabytes of data per night, systematically scanning the entire visible sky every few days.

Farah expects the Rubin Observatory to detect dozens of superluminous supernovae with chirp signatures, transforming what is currently a single landmark detection into a robust statistical sample [2]. Each chirping supernova will offer an independent test of general relativity in extreme conditions and new constraints on magnetar formation physics.

"The uniquely pristine and high-cadence LCO data allowed us to predict future bumps," Farah said of the SN 2024afav campaign [2]. With Rubin's vastly greater sky coverage and sensitivity, the next generation of chirp detections may arrive not in years, but in months.

Source: GDELT Project

Data as of Mar 13, 2026CSV

A Theory Sixteen Years in the Making

There is a satisfying narrative arc to this discovery. Daniel Kasen proposed the magnetar engine model from his office at UC Berkeley in 2010. Sixteen years later, the confirmation came from Joseph Farah — who, having completed this work, will defend his Ph.D. thesis in May 2026 and begin a Miller Fellowship at UC Berkeley, the very institution where the theory was born [2].

Andy Howell of Las Cumbres Observatory, who identified the first superluminous supernova back in 2006 and served as Farah's advisor, has now seen the field come full circle — from the initial recognition that these explosions were anomalously bright, through years of theoretical debate, to the definitive observational proof of what powers them [7].

The discovery also underscores the enduring power of general relativity. More than a century after Einstein published his field equations, the theory continues to make predictions that are confirmed in environments its creator could scarcely have imagined — from gravitational waves rippling across the cosmos to, now, the wobbling accretion disk of a newborn magnetar hidden inside a dying star's light.

"It's so remote from anything we've ever thought of," Farah reflected. "We know so little about these things" [4].

What we know now, at least, is this: when the universe's most massive stars die, some leave behind objects so extreme that only Einstein's most radical insights can describe their behavior. And for the first time, we have heard one of them being born.