This is a historic observation: the live birth of a magnetar, a type of neutron star possessing an exceptionally powerful magnetic field. This discovery finally lifts the veil on the origin of some exceptionally bright stellar explosions.
These superluminous supernovae, like SN 2024afav spotted in 2024, can shine up to ten times brighter than classical explosions. For years, scientists suspected they could be linked to the formation of magnetars, but without providing proof.
Illustration of a magnetar surrounded by a precessing accretion disk
Credit: Joseph Farah and Curtis McCully, Las Cumbres Observatory
According to the theory developed by researchers like Dan Kasen and Stan Woosley, a massive star at the end of its life collapses to produce an ultra-dense core. When this star has a powerful magnetic field, it is amplified during the collapse, creating a magnetar. At the same time, the object's rotation speeds up, like a skater pulling in their arms, potentially leading to prodigious rotation speeds.
The analysis of SN 2024afav revealed unusual patterns in its light curve, comparable to "flickering." Four oscillations did not match the traditional behavior of a supernova. To explain this unprecedented phenomenon, astronomers examined several hypotheses using data collected over 200 days after its detection.
Only the effects of Einstein's general relativity, particularly the Lense-Thirring effect, were able to faithfully reproduce these flickers. As the rapidly spinning magnetar drags spacetime around it, an accretion disk made of falling-back matter begins to wobble. This motion produces a stroboscopic effect that modulates the perceived brightness.
Accelerating over time, this oscillation generates the recorded brightness variations. Calculations indicate that the central object rotates about 238 times per second and possesses a magnetic field hundreds of thousands of billions of times more intense than Earth's, confirming its nature as a magnetar. This observation thus constitutes the long-awaited tangible proof.
For the first time, general relativity proved indispensable for describing the mechanics of a supernova, offering an elegant demonstration of the link between magnetars and superluminous supernovae. This breakthrough opens new avenues for studying the most extreme objects in the cosmos, as the researchers report in their publication in the journal
Nature.