A Superluminous Supernova Blinked Four Times—And May Reveal Einstein’s Frame-Dragging at Work

The dying star did not go quietly.

About 1 billion light-years from Earth, a titanic stellar explosion in late 2024 flared to superluminous brilliance and then, instead of fading smoothly, blinked four times. Each brightening came a little sooner than the last, in a pattern astrophysicists liken to a “chirp”—a signal whose rhythm speeds up over time.

Now, an international team reports that this strange cosmic heartbeat appears to be the imprint of a newborn neutron star twisting the fabric of spacetime as it spins. The study, published March 11 in Nature, links the flickering light of the supernova, known as SN 2024afav, to a phenomenon predicted by Albert Einstein’s theory of general relativity more than a century ago.

“We saw this superluminous supernova that didn’t behave like the others,” said Joseph R. Farah of Las Cumbres Observatory and the University of California, Santa Barbara, the paper’s lead author. “Its brightness had these four distinct bumps, and the spacing between them kept shrinking. When we modeled that pattern, the only thing that matched was Lense–Thirring precession—spacetime being dragged around a rapidly spinning neutron star.”

A clue to what powers the brightest stellar explosions

The result offers some of the clearest evidence yet that at least some of the universe’s brightest stellar explosions are powered by newly born magnetars—exotic neutron stars with magnetic fields a trillion times stronger than Earth’s. It also points to a new way to test general relativity in one of the most violent environments known: the core of an exploding massive star.

Superluminous supernovae (SLSNe) are 10 to 100 times brighter than typical stellar explosions and have puzzled astronomers since they were first identified in the mid-2000s. Many are hydrogen-poor, indicating that the star shed its outer layers before it blew apart. For over a decade, researchers have debated what powers these events, proposing engines ranging from rapidly spinning neutron stars to black holes feeding on fallback material to collisions between the ejecta and dense shells of gas surrounding the star.

SN 2024afav, spotted in December 2024 by sky surveys and then monitored intensively by Las Cumbres Observatory’s global network of 27 robotic telescopes, quickly stood out. Its peak brightness placed it firmly in the superluminous category. But as the light faded over the following months, a subtle structure emerged.

Instead of a smooth decline, the supernova displayed four pronounced rebrightenings. High-cadence observations over more than 200 days showed that these bumps were not random. They formed a quasi-periodic sequence: the interval between the first and second bump was longest, the next gap shorter, and so on—like beats in a rhythm accelerating with time.

Astrophysicists refer to that steadily increasing frequency as a chirp, borrowing a term commonly used for gravitational-wave signals from merging black holes and neutron stars. In the case of SN 2024afav, the chirp was imprinted not in gravitational waves but in visible light.

The magnetar engine—and what it couldn’t explain

To decode it, Farah and colleagues first fit the overall rise and fall of the light curve with a magnetar-powered model. In that scenario, the collapsing core of a massive star forms a neutron star that is both rapidly spinning and highly magnetized. As it slows down, the magnetar releases rotational energy that heats the expanding debris, keeping the supernova brighter for longer than radioactive decay alone would allow.

The best-fit parameters suggested an exceptionally fast newborn magnetar, spinning once every 4.2 milliseconds, with a surface magnetic field of about 1.6 × 10¹⁴ gauss—well within the magnetar range.

That engine could explain how the supernova became so luminous. It did not, by itself, explain why the light should flicker four times in a chirped sequence.

A wobbling disk and Einstein’s frame dragging

The team turned to a more intricate picture. In their model, some of the outer layers ejected in the blast remain gravitationally bound and fall back toward the compact remnant. That fallback material forms an accretion disk tilted relative to the spin axis of the magnetar.

Here, general relativity enters. According to Einstein’s theory, a spinning mass does not simply sit in spacetime; it drags spacetime around with it. This effect, known as frame dragging or Lense–Thirring precession—after Josef Lense and Hans Thirring, who calculated it in 1918—causes the orbit of nearby material to slowly wobble.

Near Earth, frame dragging is extraordinarily subtle. It has been measured using the LAGEOS and LARES satellites, whose orbital planes precess slightly over years, and by NASA’s Gravity Probe B mission, which detected minuscule changes in the direction of spinning gyroscopes.

Around a newly born neutron star rotating hundreds of times a second, the effect is far stronger.

“In the strong gravity close to a magnetar, Lense–Thirring precession can make a tilted disk wobble like a spinning top,” Farah said. “As the disk spreads and more material migrates inward, that wobble speeds up. That natural speeding-up matches the chirp we see in the light.”

If the disk’s plane is misaligned with our line of sight, each precession cycle can periodically block, scatter or reprocess light from the magnetar engine. The result, viewed from Earth, is a series of rebrightenings whose spacing reflects the changing precession period.

The researchers tested other possibilities, including purely Newtonian torques, such as those caused by a slightly oblate neutron star, and disk warping driven by the magnetar’s magnetic fields. They also considered whether clumpy material around the star could produce similar bumps through shocks alone.

“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.

D. Andrew “Andy” Howell, a senior author on the study and leader of the supernova group at Las Cumbres Observatory and UC Santa Barbara, said the match between model and data strengthens the long-standing magnetar hypothesis.

“For years we’ve suspected magnetars power these superluminous explosions, but we didn’t have a smoking gun,” Howell said. “Here, Joseph has tied the bumps in the light curve directly to the magnetar model, and explained everything with the best-tested theory in astrophysics—general relativity. It’s very compelling.”

Complications: shocks may also contribute

Other observations suggest the picture is not quite so clean. Separate, more detailed spectroscopic work on SN 2024afav, led by some of the same authors and submitted to The Astrophysical Journal, finds signs that the supernova ejecta also collided with surrounding material. Narrow, blueshifted hydrogen and helium lines—unusual for a hydrogen-poor event—appear in the spectra at about the same times as some of the bumps, indicating that shocks from ejecta slamming into a nearby shell contributed to the brightness variations.

That means the light curve likely records several overlapping processes: the steady power from a spinning magnetar, the time-variable effect of its precessing disk, and additional boosts from circumstellar interaction.

The interpretation also depends on assumptions about how the fallback disk forms and evolves, including its tilt and opacity. Astrophysicists who are cautious about using messy stellar explosions to test fundamental physics may question whether nonrelativistic processes could be ruled out more thoroughly.

The authors acknowledge those uncertainties but argue that the specific pattern of four chirped bumps, all fit by a single set of magnetar and disk parameters, is difficult to reproduce without invoking frame dragging.

Why this matters for the next era of sky surveys

Beyond explaining a single object, the discovery highlights the growing power of time-domain astronomy. Las Cumbres Observatory’s global, robotic network allowed near-continuous monitoring from multiple longitudes, capturing subtle changes in brightness that a single observatory might have missed. The project also received support from the National Science Foundation’s AI Institute for Artificial Intelligence and Fundamental Interactions, underscoring the role of automated tools in sifting through torrents of survey data.

Farah and his colleagues expect that the upcoming Vera C. Rubin Observatory in Chile, which will image the entire visible sky every few nights when it begins full operations later this decade, will uncover many more candidates.

“With Rubin, we should find dozens more of these chirping supernovae,” Farah said. “Each one will give us another chance to study newly born magnetars and to see how general relativity plays out in their extreme environments.”

For now, SN 2024afav stands as a rare case in which the death of a distant star seems to have left a readable trace of what happened deep in its core. Its fading light, modulated by a wobbling disk of debris, appears to carry the imprint of spacetime itself being dragged around one of the universe’s most extreme objects.