The recent research domain of asteroseismology refers to the study of
the internal structure of pulsating stars through the interpretation of their
frequency spectra. Asteroseismologists make great use of the oscillations
to probe the stellar interior, which is not directly observable. The basic
principles of asteroseismology are very much alike those developed by earth
No part of the Universe is more difficult to observe directly than the interior
of the stars. The reason why stellar interiors can be probed from oscillations
is that different oscillation modes penetrate to different depths inside the
star. Asteroseismology is the only available method so far to derive the
internal structure of the stars with high precision.
Astrophysicists at the Institute of Astronomy of the University of Leuven play a
central role in the interpretation of oscillation data of B-type stars. These
are massive stars, with masses between 3 and 30 times the mass of the Sun.
Stars heavier than roughly 9 solar masses will explode as a supernova at the end
of their life. Thanks to such explosions, the interstellar medium is enriched
with products of the nuclear burning in the stellar core, i.e. with chemical
elements heavier than hydrogen and helium.
Oscillations can be excited in stars when thermal energy is converted
into kinetic energy of pulsation. Similarly as for any heat engine, this
proces is effective if heat is absorbed in the high temperature phase of
oscillation and emitted when the temperature is low. The main mechanism
for stars is the net conversion of radiation energy into pulsational
energy in the surface layers of some classes of stars.
The resulting oscillations are usually studied under the assumption that
they are small, and that the star is isolated and spherically
symmetric. At the Institute of Astronomy, several basic properties of
stellar oscillations have been developed and clarified, and we are
interested in the behaviour of oscillating stars when the above
assumptions are relaxed. In particular, we develop asymptotic
representations of stellar oscillations, which are very useful for
gaining insight into the deep layers of stars, and study the influence
of stellar rotation and nonlinear effects on the oscillations.
Furthermore, as multiple stars are very common, we investigate stellar
tides and the effects of a tidal force on oscillating stars.
For a more detailed basic text on asteroseismology of massive stars (including
references), click here.
To retrieve the discriminant code developed at the IvS to identify non-radial
oscillation modes from line-profile variations, click
Tim Van Hoolst
Joris De Ridder
Leuven Mercator telescope
Belgian Asteroseismology Group
Global Oscillation Network Group
Whole Earth Telescope Project
Delta Scuti Network
Birmingham Solar Oscillations Network
European Network of Excellence in AsteroSeismology
Space missions for asteroseismology: