Astronomers discover power source behind some of space's brightest supernovae

(CN) — Astronomers confirmed the power source behind some of the brightest supernovae in the night sky comes from the creation of highly magnetized, spinning neutron stars known as magnetars after recording the birth of one, according to a new study published in the journal Nature on Wednesday.

These superluminous supernovae can be at least 10 times brighter than average supernova and have puzzled astronomers since they were discovered in the early 2000s. Originally, astronomers believed them to be the end result of a massive star explosion 25 times the mass of our sun, but their brightness remained much longer than would be expected after their iron cores collapsed and their outer layers were blown off.

A supernova is a massive explosion that happens when a star collapses at the end of its life, releasing energy and light as its core shrinks into a dense ball, such as a magnetar, that fuels the luminous events in the cosmos.

The study published on Wednesday confirms a theory first proposed by University of California, Berkeley astrophysicist Dan Kasen in 2010 that magnetars were powering the superluminous supernovae. It also establishes a new phenomenon in supernovae’s light curves that researchers describe as the “chirp,” or bump.

“For years the magnetar idea has felt almost like a theorist’s magic trick — hiding a powerful engine behind layers of supernova debris,” Kasen said in a press release. “It was a natural explanation for the extraordinary brightness of these explosions, but we couldn’t see it directly. The chirp in this supernova signal is like that engine pulling back the curtain and revealing that it’s really there.”

Kasen theorized, at the suggestion of physicist Stanford Woosley, that when a massive star collapsed, it crunched most of its mass into a neutron star. But if the star had a strong magnetic field, it would intensify during its collapse and form a magnetar, becoming exponentially more powerful than typical neutron stars.

Magnetars, which are only about 10 miles in diameter, can spin up to 1,000 times per second. As they do so, their magnetic field can accelerate charged particles that crash into the debris from an exploding supernova, thus increasing their brightness, the researchers explain

UC Santa Barbara graduate student Joseph Farah confirmed the connection between magnetars and superluminous supernovae after analyzing data at the Las Cumbres Observatory from an exploding star discovered in December 2024. Scientists tracked and monitored the supernova, located about 1 billion light-years from the Earth, for more than 200 days.

Farah, the lead author of the Nature study, noted that the supernova’s brightness peaked about 50 days after the explosion, but it didn’t gradually fade away. Instead, the brightness oscillated downward, producing an unprecedented series of four chirps in its light curve.

Farah and his 13 coauthors proposed that the theory of general relativity can explain the unusual bumps in the light curve of the supernova that link it to a magnetar.

The research is definitive evidence of a magnetar forming in the aftermath of a supernova core collapse, said Alex Filippenko, an astronomy professor at UC Berkeley who coauthored the new study.

“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,” he said in release. “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.”

Researchers observed that some of the debris from the 2024 supernova explosion fell back toward the newborn magnetar, creating an asymmetric disk of material that spins at a lopsided angle, leading to a misalignment of the magnetar’s spin axis. Because a spinning object drags space-time with it, known as the Lense-Thirring precession, the magnetar caused its disk of debris to wobble — which blocks and reflects the light — ultimately creating the chirping effect, the scientists wrote.

“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 in a release. “It is the first time general relativity has been needed to describe the mechanics of a supernova.”

Farah said he anticipates discovering dozens more chirping supernovae in the cosmos as the new Vera C. Rubin Observatory, located in Chile, is expected to come online this year.

“This is the most exciting thing I have ever had the privilege to be a part of,” Farah said. “This is the science I dreamed of as a kid. 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.”