Introduction
The purpose of helio- and asteroseismology is very similar to trying
to determine the shape and construction of musical instruments from the
sounds that they make. The way in which something can vibrate, whether it
is a star or an elastic band, can say a lot about what it is. We all know
how to recognize the difference between a
drum and an organ or
a bell. In helioseismology
we try to be much more precise and quantitative in what we determine about
the Sun : which is something like trying to hear the difference between
a Stradivarius and an ordinary violin.
The term helioseismology comes from a combination of three words :
- helios : from the classical Greek which means Sun or light.
- seismos : also from Greek meaning tremor.
- logos : meaning reasoning or discourse.
So literally translated helioseismology is the study of solar tremors,
just as geoseismology is the study of earthquakes, and in particular
the use of the information on how eartquakes propagate to measure the internal
structure of the earth. By looking at tremors on the solar surface it
is possible to measure what the Sun is like, deep in its interior !
How this is done is described on the page on solar
oscillations. You can also read about how we observe
the Sun and other stars.
Asteroseismology is the study of oscillations on distant stars for which
we use much the same techniques that are used in helioseismology. It is
just made more difficult by the fact that stars are a lot further away
than the Sun. You can read more about
asteroseismology done at Aarhus university here.