For the first time, astronomers have witnessed the birth of one of the most powerful magnets in the universe – a magnetar – at the center of an unusually bright supernova, thanks to an effect first predicted by Albert Einstein.
Researchers say this exciting discovery marks the first time that general relativity has been needed to explain the dynamics of an exploding star.
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For more than a decade, researchers have predicted that magnetar formation could help explain “hyperluminous supernovae,” which shine at least 10 times brighter than most other stellar explosions. In theory, these unusual light shows could occur if a magnetar formed at the center of a supernova, since the supercharged magnetism of stellar remnants could further accelerate the ejection of charged particles. But so far no one has been able to prove this.
But in a new study published March 11 in the journal Nature, astronomers have found evidence of the phenomenon occurring inside a superluminous supernova called SN 2024afav that exploded into the night sky in December 2024.
Analyzing the light curve of SN 2024afav, which remained bright for more than 200 days and was observed by more than 20 telescopes around the world, the researchers found that after reaching its brightness peak, the explosion did not gradually fade like other supernovae. Instead, its brightness brightened and dimmed at least four times, which researchers claim is evidence of magnetar involvement.
“This is conclusive evidence that magnetars formed as a result of the collapse of ultraluminous supernova nuclei,” study co-author Alexei Filipenko, an astronomer at the University of California, Berkeley, said in a statement. It’s also the first time we’ve seen a magnetar come into being, “which is really exciting,” he added.
Astronomers have seen other phenomena in the past that could have given rise to magnetars, such as the merger of two small neutron stars. But this new study provides the first direct evidence of the birth of magnetars.
The researchers also estimated the physical characteristics of newborn magnetars based on the data they analyzed. They believe that the star probably rotates every 4.2 milliseconds (238 times per second) and that its magnetic field is roughly 300 trillion times larger than Earth’s magnetic field, which protects our planet from potentially dangerous solar storms.
“Strobe space lighthouse”
The wobble in SN 2024afav’s light curve is likely due to an accretion disk surrounding the newly formed magnetar. This disk is made up of gas and dust from an exploding star, which is pulled back toward the star’s remains by its massive gravity. This is similar to the disks seen around black holes, but it is almost certainly asymmetrical, so it is not aligned with the magnetar’s axis of rotation.
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According to Einstein’s theory of general relativity, such a disk wobbles about the magnetar’s rotation axis, undergoing an effect known as Lens-Surling precession, brightening and dimming as it passes through the line of sight between the stellar remnant and Earth.
“The wobbling disk could periodically block or reflect light from the magnetar, turning the entire system into a strobe lighthouse in space,” UC Berkeley representatives said in a statement.
The researchers detected four fluctuations in the supernova’s light curve, each new fluctuation shorter and less intense than the last. This type of oscillation, similar to the rhythm of the songs of several birds, led the researchers to call the oscillations “chirps,” and is what would be expected from the lens-tilling effect.
“We tested several ideas, including pure Newtonian effects and precession driven by the magnetar’s magnetic field, but lens-tilling precession was the only one whose timing matched perfectly,” study lead author Joseph Farrar said in a statement. He is an incoming researcher at the University of California, Berkeley, and a doctoral candidate at California’s Las Cumbres Observatory, where SN 2024afav was first discovered. “it is [also] For the first time, general relativity was needed to describe the dynamics of supernovae. ”
For the researchers who first proposed the idea, the new findings are a “smoking gun” that proves they were right all along, UC Berkeley representatives wrote.
“For many years, the magnetar idea has felt like a sleight of hand by theorists hiding a powerful engine behind a layer of supernova debris,” Dan Kasen, an astrophysicist at the University of California, Berkeley, who was one of the original proponents of the Lens-Tilling hypothesis but was not involved in the new study, said in a statement. “This supernova signal chirp is like an engine pulling back a curtain to reveal that it’s actually there.”
This new discovery does not mean that all ultraluminous supernovae are connected to magnetars. That’s because other researchers have already shown that these bright explosions can also be caused by a “cocoon” of gas and dust around an exploding star. But the research team now plans to investigate which of these causes is most common across the universe.
Researchers expect to discover dozens of similar “singing” supernovae over the next few years using the newly operational Vera C. Rubin Observatory in Chile, which they hope will be well-suited to detect this unstable signal.
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