Helio- and Asteroseismology, whose etymologies have ancient Greek roots, indicate the study of the internal structure and dynamics of the Sun and
other stars from observations of their resonant vibrations. These vibrations - or oscillations -
manifest themselves in small motions of the visible surface of the star and, like the seismic waves generated by earthquakes in the Earth,
provide us with valuable information about the pervaded internal layers.
Oscillations have several advantages over
all the other observables:
pulsational instability has been detected in
stars in all the
evolutionary stages and of different spectral type from main-sequence to the
white dwarf cooling sequence;
frequencies of oscillations can be measured with high accuracy and
depend in very simply way on the equilibrium structure of the model;
different modes propagate through different layers of the interior of a star.
Thus, a sufficiently rich spectrum of observed resonant modes
permit the probing of internal
conditions and lead to test and revise theories of stellar
structure and evolution.
Since a correct understanding of stars' evolution is a corner-stone of
modern astrophysics, these endeavors are fundamentally important to the whole of astrophysics.
.png)
