For more than a decade, some of the brightest stellar explosions ever observed have defied explanation. Known as superluminous supernovae, these rare blasts can shine up to 100 times brighter than typical supernovae and remain luminous far longer than astronomers expected. Now, a new study says it solves the mystery of what powers these brilliant cosmic phenomena.
In research published this week in Nature, astronomers at the University of California, Berkeley report evidence that these extraordinary explosions are driven by magnetars—ultra-dense neutron stars with magnetic fields trillions of times stronger than Earth’s.
The discovery comes from a detailed analysis of an unusual supernova whose light flickered in a series of rhythmic pulses, a signal researchers describe as a cosmic “chirp.” Those oscillations, the team says, appear to be the long-sought signature of a newborn magnetar hidden deep within the exploding star.
Even more striking, the pattern can be explained only by Einstein’s general theory of relativity, marking what researchers say may be the first time relativistic effects have been required to describe the mechanics of a supernova.
Superluminous Supernovae
Superluminous supernovae are an unusual category of stellar explosions that remain bright far longer than expected. They were once hypothesized to represent the end state of massive stars with roughly 25 times the mass of the Sun. Sixteen years ago, UC Berkeley theoretical physicist Dan Kasen first proposed that magnetars were responsible for their enduring brightness. Along with collaborator Lars Bildsten—and reflecting independent work by UC Santa Cruz astrophysicist Stan Woosley—Kasen helped advance one of the earliest theoretical explanations for what might power these unusual events.
During a massive star’s final moments, it collapses into a superdense neutron star—an extremely compact object that spins rapidly. If the original star possessed a particularly strong magnetic field, the resulting neutron star can become a magnetar, a type of neutron star with an extraordinarily powerful magnetic field. Kasen’s theory proposed that the rapid rotation of a magnetar could accelerate charged particles colliding with the surrounding supernova debris, injecting additional energy that increases the explosion’s brightness—matching what astronomers observe in superluminous supernovae.
Analyzing the Chirps
New research led by UC Berkeley’s Joseph Farah, working in Kasen’s group, now provides evidence supporting the connection between magnetars and Type I superluminous supernovae through a detailed analysis of the 2024 supernova SN 2024afav. The research team proposes that a magnetar produced measurable bumps in the supernova’s light curve—features they describe as “chirps”—that can be explained using general relativity.
“What’s really exciting is that this is definitive evidence for a magnetar forming as the result of a superluminous supernova core collapse,” said co-author Alex Filippenko, a UC Berkeley distinguished professor of astronomy. “The basis of Dan Kasen and Stan Woosley’s model is that all you need is the energy of the magnetar deep within, and a good fraction of it will get absorbed, and that’ll explain why the thing is superluminous. What had not been demonstrated was that a magnetar did in fact form in the middle of the supernova, and that’s what Joseph’s paper shows.”
“For years, the magnetar idea has felt almost like a theorist’s magic trick—hiding a powerful engine behind layers of supernova debris. It was a natural explanation for the extraordinary brightness of these explosions, but we couldn’t see it directly,” Kasen also said of the work in a statement. “The chirp in this supernova signal is like that engine pulling back the curtain and revealing that it’s really there.”
Supernova SN 2024afav
When the supernova was first discovered in December 2024, it immediately drew the attention of astronomers. The Las Cumbres Observatory, a global network of 27 telescopes, observed the event for more than 200 days as its luminosity varied roughly one billion light-years from Earth.
Instead of showing the typical gradual fading seen in most supernovae, SN 2024afav dimmed in a series of four oscillating bumps. While astronomers have occasionally detected small bumps in supernova decay—often attributed to shockwaves colliding with surrounding gas—no previous observation had revealed as many as four.
Farah’s model suggests an unusually shaped system in which the asymmetrical accretion disk surrounding the newborn neutron star does not properly align with the magnetar’s spin axis. As the magnetar’s rotation drags the disk along, this misalignment produces a wobbling motion that creates a strobing effect from Earth’s vantage point—producing what researchers identify as a “chirp.”
“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. “It is the first time general relativity has been needed to describe the mechanics of a supernova.”
Additionally, estimates of the neutron star’s spin period and magnetic field strength suggest it is very likely a magnetar.
Continuing to Scan for Supernovae
“I think Joseph has found the smoking gun,” said Howell, a senior scientist at LCO and UCSB adjunct professor of physics. “He’s tied the bumps into the magnetar model and explained everything with the best-tested theory in astrophysics — general relativity. It is incredibly elegant.”
“To see a clear effect of Einstein’s general theory of relativity is always exciting, but seeing it for the first time in a supernova is especially rewarding,” Filippenko added.
While the discovery represents a significant step forward—and likely explains this particular event—the team acknowledges that other superluminous supernovae may arise from different mechanisms. Another possibility, Kasen suggests, is that a core collapse forming a black hole could produce a similar effect if accompanied by a misaligned accretion disk.
“We don’t know what fraction of Type I superluminous supernovae might be powered by circumstellar material, but it’s definitely a smaller fraction than we previously thought, because this discovery clearly accounts for some of them,” Filippenko said.
The team is optimistic that new data from the Vera C. Rubin Observatory—which released its first test images last year—will help astronomers discover more of these chirping supernovae.
“This is the most exciting thing I have ever had the privilege to be a part of. This is the science I dreamed of as a kid,” Farah said. “It’s the universe telling us out loud and in our face that we don’t fully understand it yet, and challenging us to explain it.”
The paper, “Lense–Thirring Precessing Magnetar Engine Drives a Superluminous Supernova,” appeared in Nature on March 11, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.