Solution Proposed to Mystery of Incredibly Strong White Dwarf Magnetic Fields

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Huge White Dwarf Magnetic Fields

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Illustration of the origin of electromagnetic fields in white overshadows in close binaries (to be checked out counter clockwise). The electromagnetic field appears when a taking shape white dwarf accretes from a buddy star and as an effect begins to spin quickly. When the white overshadows field gets in touch with the field of the secondary star, mass transfer picks up a fairly brief amount of time. Credit: Paula Zorzi

  • University of Warwick astronomer co-authors brand-new research study in Nature Astronomy that proposes a service to long-running concern of how white dwarf stars produce electromagnetic fields
  • An eager beaver system, comparable to how Earth creates its electromagnetic field, might be the response
  • This research study reveals that often really comparable systems can operate in really various huge things.

An eager beaver system might describe the exceptionally strong electromagnetic fields in white dwarf stars according to a global group of researchers, consisting of a University of Warwick astronomer.

One of the most striking phenomena in astrophysics is the existence of electromagnetic fields. Like the Earth, stars and excellent residues such as white overshadows have one. It is understood that the electromagnetic fields of white overshadows can be a million times more powerful than that of the Earth. However, their origin has actually been a secret given that the discovery of the very first magnetic white dwarf in the 1970s. Several theories have actually been proposed, however none has actually had the ability to describe the various event rates of magnetic white overshadows, both as specific stars and in various binary star environments.

This unpredictability might be solved thanks to research study by a global group of astrophysicists, consisting of Professor Boris Gänsicke from the University of Warwick and led by Professor Dr. Matthias Schreiber from Núcleo Milenio de Formación Planetaria at Universidad Santa María in Chile. The group revealed that an eager beaver system comparable to the one that creates electromagnetic fields on Earth and other worlds can operate in white overshadows, and produce much more powerful fields. This research study, part-funded by the Science and Technology Facilities Council (STFC) and the Leverhulme Trust, has actually been released in the distinguished clinical journal Nature Astronomy.

Crystallizing Magnetic White Dwarf

A taking shape magnetic white dwarf accreting from the wind of its buddy star. Credit: Paula Zorzi

Professor Boris Gänsicke of the Department of Physics at the University of Warwick stated: “We have known for a long time that there was something missing in our understanding of magnetic fields in white dwarfs, as the statistics derived from the observations simply did not make sense. The idea that, at least in some of these stars, the field is generated by a dynamo can solve this paradox. Some of you may remember dynamos on bicycles: turning a magnet produces electric current. Here, it works the other way around, the motion of material leads to electric currents, which in turn generate the magnetic field.”

According to the proposed eager beaver system, the electromagnetic field is created by electrical currents triggered by convective movement in the core of the white dwarf. These convective currents are triggered by heat leaving from the strengthening core.

“The main ingredient of the dynamo is a solid core surrounded by a convective mantle — in the case of the Earth, it is a solid iron core surrounded by convective liquid iron. A similar situation occurs in white dwarfs when they have cooled sufficiently,” describes Matthias Schreiber.

The astrophysicist describes that at the start, after the star has actually ejected its envelope, the white dwarf is really hot and made up of liquid carbon and oxygen. However, when it has actually adequately cooled, it starts to take shape in the center and the setup ends up being comparable to that of the Earth: a strong core surrounded by a convective liquid. “As the velocities in the liquid can become much higher in white dwarfs than on Earth, the generated fields are potentially much stronger. This dynamo mechanism can explain the occurrence rates of strongly magnetic white dwarfs in many different contexts, and especially those of white dwarfs in binary stars” he states.

Thus, this research study might fix a decades-old issue. “The beauty of our idea is that the mechanism of magnetic field generation is the same as in planets. This research explains how magnetic fields are generated in white dwarfs and why these magnetic fields are much stronger than those on Earth. I think it is a good example of how an interdisciplinary team can solve problems that specialists in only one area would have had difficulty with,” Schreiber includes.

The next actions in this research study, states the astrophysicist, are to carry out a more comprehensive design of the eager beaver system and to check observationally the extra forecasts of this design.

Reference: “The origin and evolution of magnetic white dwarfs in close binary stars” by Matthias R. Schreiber, Diogo Belloni, Boris T. Gänsicke, Steven G. Parsons and Monica Zorotovic, 29 April 2021, Nature Astronomy.
DOI: 10.1038/s41550-021-01346-8

The research study likewise got assistance through an STFC Ernest Rutherford Fellowship.



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