The universe’s brightest supernovae are turbocharged by newborn magnetars

The universe’s brightest supernovae are turbocharged by newborn magnetars

By Joseph Howlett edited by Lee Billings

The death of each star is dramatic. Superluminous supernovae take theater to another level.

In the early 2000s, scientists first observed these remarkable cataclysms, which can shine much longer and be more than 10 times brighter than a normal supernova. And since then, they have been wondering what physical process explains the exceptional and persistent dazzling of these supernovae.

Now they know it. In an article published today in the journal Nature, Astrophysicists have discovered the true source of a superluminous supernova: radiation emitted by a city-sized, freshly formed, highly magnetized, rapidly rotating ball of neutrons, a so-called magnetar. In addition to solving the puzzle of superluminous supernovae, this is also the first time that scientists have witnessed the birth of a magnetar. And what gave it all away was a strange quirk of Einstein’s theory of general relativity.

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“It’s so far from anything we’ve ever thought about,” says Joseph Farah, a graduate student affiliated with the Las Cumbres Observatory (LCO) and the University of California, Santa Barbara, who led the study. “We know so little about these things. »

What East It is known that when a massive star exhausts its fuel, it collapses in on itself and explodes, leaving behind an expanding and slowly cooling cloud of radioactive gas and debris with a tiny stellar remnant at the center. When such a star had a mass 10 to 25 times that of our sun, this remnant is usually a neutron star. They are the strangest bits of matter in the cosmos – a teaspoon of their matter weighs as much as Mount Everest – making neutron stars the site of some of the most extreme physics there is.

Neutron stars become particularly extreme when they rotate rapidly, emitting lighthouse-like beams of radiation from their poles; astronomers call these objects pulsars. And magnetars are the most extreme of all: most of them are newborn pulsars that have magnetic fields up to 1,000 times stronger than normal.

Although theorists already had the idea that the tumultuous birth of a magnetar could help explain superluminous supernovae, closing the deal proved difficult. A potential breakthrough occurred in late 2024 with the eruption of a new superluminous supernova, SN 2024afav, about a billion light years from Earth. Monitored for 200 days by LCO astronomers, SN 2024afav’s brightness dipped periodically, oscillating back and forth, with the time between dips becoming shorter and shorter over the course of the measurement.

Farah and her co-authors went to the board looking for explanations for this specific pattern. They only chose one that could explain it. As a magnetar spins on its axis at near the speed of light, its immense magnetic field twists, twists and turns to emit powerful radiation. The energy from this astrophysical engine ignites the surrounding ejected gas, thereby increasing the brightness and longevity of the supernova.

But what caused these stellar embers to wax and wane? The answer comes down to how the spinning dead star dragged space and time in its wake.

The magnetar was initially surrounded by a swirling disk of material, channeled from its inner edge toward the stellar remnant. The disk was slightly tilted relative to the axis of rotation of the magnetar, and the violent space-time vortex it created caused the disk to spin around it. From a distance, this consequence of general relativity, called “Lense-Thirring precession,” made the entire system look like a top wobbling on a table.

From Earth’s vantage point, just along the distant magnetar’s equator, the flickering disk acted like the shutter of a film projector, periodically obstructing our view of the supercharging dead star SN 2024afav. As the days passed and the magnetar ate away at its disk, this torus of matter shrank inward. This accelerated the shutter effect, making the dips in light more and more frequent until the disk disappeared.

According to the authors, this stellar origin story fits the data better than anything they could imagine. This makes it the surest evidence of what actually happens at the center of a superluminous supernovae. “Other possible energy sources would not produce such a model,” says Daniel Kasen of the University of California, Berkeley, one of the astrophysicists who first proposed the magnetar explanation in 2010 and who is credited with providing a useful discussion in the new paper. “A magnetar can act as a powerful engine that illuminates the supernova with extraordinary brightness.”

This confirmation makes magnetars another cosmic laboratory for testing general relativity. “Everything about the system is extreme,” says Adam Ingram, an astrophysicist at the University of Newcastle in England, who served as a peer reviewer for the study. “The gravitational field is strong enough for the most exotic predictions of general relativity to have significant effects.”

Over its lifetime, the newly operational Vera C. Rubin Observatory in Chile will see millions of supernovae, including many more of these rare events. And wherever general relativity is visible in the world, Farah says, there is an opportunity to understand it better – and perhaps even find new cracks in the edifice of Einstein’s larger theory, from which new ideas might arise. “This means we can test one of our fundamental theories of reality in one of the most extreme environments in the universe,” he says.

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