Starquake data is revealing ancient “fossil fields” responsible for stellar magnetism that persist from a star’s birth until its final moments as a burnt-out white dwarf, breathing new life into the discarded fossil field theory.
Published in a recent paper in Astronomy & Astrophysics, a new theoretical model from an international team of researchers, led by Institute of Science and Technology Austria (ISTA) PhD candidate Lukas Einramhof, uses starquakes to connect the magnetism of white dwarfs to that of dying red dwarfs.
According to the team, stellar magnetic fields may form very early on and persist as fossil fields even after the final transformation into a white dwarf, migrating from the core to the surface over immense periods of time.
Charting Stellar Magnetic Evolution
While the billions of years that stars can persist are difficult for humans to fully appreciate, their active existence is still finite, eventually burning out as white dwarf husks or exploding as supernovae.
Violent stellar oscillations, known as starquakes, provided essential asteroseismic data, allowing the researchers to connect the magnetic fields at the cores of dying red dwarfs to the surface magnetic fields of white dwarfs as fossil-field remnants.
“The magnetic field in a star is important for how the star works on the inside and how long it lives and evolves,” said lead author Lukas Einramhof. “Generally, more of the older white dwarfs tend to be more magnetic than younger white dwarfs.”
Explaining how the magnetic field develops on a star that has been dead for millions of years requires looking back in time at its evolution. While other researchers have considered magnetic fields at various evolutionary points, the ISTA team is connecting those dots to chart the course of stellar magnetic evolution.
Looking Through Starquakes
Much like geologists on Earth use seismic data to view the interior of our planet, asteroseismology provides a glimpse into the interiors of red dwarfs through starquake observations, revealing magnetic fields in their cores. This compares to surface fields observed in white dwarfs. In the starquake data, the team found new support for the largely discarded theory of fossil fields.
“Because a white dwarf is the exposed core of a red giant that has shed its outer layers, these different observations essentially examine the same region of a star’s interior at different evolutionary stages,” Einramhof said. “If the magnetic field observed during the red giant phase is the same as the one that evolves to be observed at the surface of the white dwarf, then the fossil field theory can explain and connect the observations.”
The team’s assertions go beyond the red dwarf’s magnetic field reaching the surface and suggest that the field extends much further, back to the star’s earliest stages.
From Starquakes to Archeoastronomy
“To connect the magnetic fields observed at the surface of older white dwarfs with the ones found at the core of their red giant progenitors, a larger fraction of the star must be magnetized,” said Einramhof. “However, this doesn’t mean the stars are more strongly magnetized, only that the magnetic fields must already reach a larger portion of their core.”
The team’s new simulation indicates that stellar magnetic fields form as hollow shells, with the strongest fields at the shell’s surface rather than at the star’s deepest core. Although the model is based on objects far beyond our solar system, the researchers say their end goal is to better understand our own Sun. Strong magnetic fields could even extend the Sun’s life beyond current expectations, they say.
“We still don’t know whether the Sun’s core is magnetic. Even though it’s our own star, we’re practically blind to what happens at its center,” Einramhof concluded.
“Current predictions assume that the Sun’s core is not magnetic,” he adds, noting that “if it turns out to be, this information would change everything we know and all the models we’ve based our work on.”
The paper, “Magneto-Archeology of White Dwarfs: Revisiting the Fossil Field Scenario with Observational Constraints During the Red Giant Branch,” appeared in the Astronomy & Astrophysics on April 14, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.