[en] When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much of the star's radius. Conservation of angular momentum requires that the cores of these stars rotate faster than their envelopes; indirect evidence supports this. Information about the angular-momentum distribution is inaccessible to direct observations, but it can be extracted from the effect of rotation on oscillation modes that probe the stellar interior. Here we report an increasing rotation rate from the surface of the star to the stellar core in the interiors of red giants, obtained using the rotational frequency splitting of recently detected `mixed modes'. By comparison with theoretical stellar models, we conclude that the core must rotate at least ten times faster than the surface. This observational result confirms the theoretical prediction of a steep gradient in the rotation profile towards the deep stellar interior.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Beck, Paul G; Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
Montalban Iglesias, Josefa ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Kallinger, Thomas; Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
De Ridder, Joris; Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
Aerts, Conny; Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
García, Rafael A; Laboratoire Astrophysique, Instrumentation et Modélisation (AIM), CEA/DSM--CNRS--Université Paris Diderot ; Institut de Recherche sur les lois Fondamentales de l'Univers/Service d'Astrophysique (IRFU/Sap), Centre de Saclay, 91191 Gif-sur-Yvette Cedex, France
Hekker, Saskia; Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
Dupret, Marc-Antoine ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Mosser, Benoit; Laboratoire d'études spatiales et d'instrumentation (LESIA), CNRS, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon Cedex, France
Eggenberger, Patrick; Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
Stello, Dennis; Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney 2006, Australia
Elsworth, Yvonne; School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
Frandsen, Søren; Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
Carrier, Fabien; Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
Hillen, Michel; Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
Gruberbauer, Michael; Department of Astronomy and Physics, Saint Marys University, Halifax, NS B3H 3C3, Canada
Christensen-Dalsgaard, Jørgen; Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
Miglio, Andrea ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Valentini, Marica ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Bedding, Timothy R; Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney 2006, Australia
Kjeldsen, Hans; Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
Girouard, Forrest R; Orbital Sciences Corporation/NASA Ames Research Center, Moffett Field, 94035 California, USA
Hall, Jennifer R; Orbital Sciences Corporation/NASA Ames Research Center, Moffett Field, 94035 California, USA
Ibrahim, Khadeejah A; Orbital Sciences Corporation/NASA Ames Research Center, Moffett Field, 94035 California, USA
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