Scientists have uncovered the long-sought mechanism behind low-field magnetars, showing that supernova fallback material drives the Tayler-Spruit dynamo.
This process, once purely theoretical, has now been confirmed through numerical simulations, explaining how these stars develop complex internal magnetic fields.
Unraveling the Universe’s Strongest Magnetic Fields
An international team of scientists has modeled how the strongest magnetic fields in the universe form and evolve.
Led by researchers from Newcastle University, the University of Leeds, and institutions in France, the study was published on February 4 in Nature Astronomy. The team identified the Tayler-Spruit dynamo — triggered by the fallback of supernova material — as the key mechanism behind the formation of low-field magnetars. This discovery solves a long-standing mystery that has puzzled scientists since low-field magnetars were first identified in 2010.
Using advanced numerical simulations, the researchers mapped the magneto-thermal evolution of these stars. Their findings show that a specific dynamo process within the proto-neutron star generates these relatively weaker, yet complex, magnetic fields.
How Supernova Material Shapes Magnetars
Dr. Andrei Igoshev, the study’s lead author and a Research Fellow at Newcastle University’s School of Mathematics, Statistics, and Physics, explained:
“Neutron stars are born in supernova explosions. Most of the external layers of a massive star are removed during the supernova, but some material falls back making the neutron star to spin faster. Researchers show that this process plays a very important role in the formation of a magnetic field via the Tayler-Spruit dynamo mechanism. This mechanism was suggested theoretically nearly a quarter of a century ago, but it was only recently reproduced using computer simulations. The magnetic field formed via this mechanism is very complicated with an internal field inside the start which is much stronger than the external.”
The Power of Magnetars’ Extreme Fields
Magnetars are known to have enormous magnetic fields which are hundreds trillions of times stronger the Earth’s magnetic fields. Due to these fields, magnetars are bright and variable sources of X-ray radiation. Some of less magnetized stars also have similar X-ray emissions. These less magnetized stars are known as low-field magnetars. Dynamo is a mechanism which converts plasma motion into magnetic fields.
Pushing the Boundaries of Astrophysics
Dr. Igoshev is establishing a new research group at Newcastle University to further investigate complicated magnetic fields of neutron stars.
Reference: “A connection between proto-neutron-star Tayler–Spruit dynamos and low-field magnetars” by Andrei Igoshev, Paul Barrère, Raphaël Raynaud, Jérome Guilet, Toby Wood and Rainer Hollerbach, 4 February 2025, Nature Astronomy.
DOI: 10.1038/s41550-025-02477-y
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