7 September 2006
7 September 2006
Speaker: Joergen Christensen-Dalsgaard (University of Aarhus, Denmark)
Title:Helio- and asteroseismology: windows on stellar interiors
James Arthur Lecture
Abstract:Stellar surface layers are impenetrable to electromagnetic radiation.
Hydrodynamic waves, however, travel with little attenuation through
stellar interiors and their properties, as observed on stellar surfaces,
therefore provide information about the internal properties of the star.
This forms the basis for helio- and asteroseismology, analysing the
surface manifestations of such waves. Over the past three decades
helioseismology has yielded increasingly detailed information about the
structure and dynamics of the solar interior and has allowed tests of
subtle properties of the physics of the solar plasma. More recently,
local helioseismology has allowed the study of subsurface structure of
active regions as well as complex subsurface flows, sometimes characterized
as Solar Subsurface Weather; remarkably, it has also been possible to
investigate the properties of active regions on the far side of the Sun.
Asteroseismology, particularly of solar-like stars, has come under way
more slowly, owing to the obvious difficulties of observing very small
signals in distant stars. Studies of solar-like oscillations are now
at a stage corresponding roughly to the state of helioseismology 25 years ago.
However, the observational capabilities are developing rapidly,
and we can expect extensive investigations of a broad range of stars
over the next decade, providing a much more secure basis for our
so far somewhat shaky understanding of the details of stellar evolution.
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