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Probing the innards of stars

American Association for the Advancement of Science

Studying starlight from red giants has provided insights into the makeup of a star's internal magnetic field - a region that has been notoriously hard to study. The technique applied here could be used to probe the internal magnetic fields in certain star types, providing a clearer picture of the influence of stellar magnetism on a star's evolution. While magnetic fields on the surfaces of stars can be observed, those within the star have so far remained out of reach. Recent studies with the Kepler satellite have identified red giant stars with mysteriously "dampened" internal activity, or vibrations. Here, Jim Fuller and colleagues showed it was possible to probe the interiors of these stars using asteroseismology, a technique that involves interpreting variations in light emitted from a star as due to sound waves from its interior. Based on their analysis, Fuller and colleagues say that the magnetic fields of the red giants they studied caused sound waves inside them to become trapped in the star's interior - an explanation for the mysterious damping of certain vibration modes in the Kepler observations. The study provides a plausible explanation for why some red giants have "depressed" vibration modes and will help scientists better understand the properties and evolution of stellar magnetic fields.

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Article #7: "Asteroseismology can reveal strong internal magnetic fields in red giant stars," by J. Fuller; L. Bildsten at California Institute of Technology in Pasadena, CA; J. Fuller; M. Cantiello; L. Bildsten at University of California, Santa Barbara in Santa Barbara, CA; D. Stello at University of Sydney in Sydney, NSW, Australia; D. Stello at Aarhus University in Aarhus, Denmark; R.A. Garcia at CNRS in Gif-sur-Yvette, France; R.A. Garcia at Université Paris Diderot in Gif-sur-Yvette, France.

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