A Slow Means of Energy Transport
Once energy is produced in the core of the Sun, it needs a way to
travel from the solar center to the outer regions. The physical transport
of energy from its production site to the surrounding regions can be done
in a number of ways. However, for a star like the Sun, the most efficient
means of transferring energy near the core is by radiation. Consequently,
the region surrounding the core of the Sun is known as the radiation
zone. Throughout this region of the solar interior, energy, in the form of
radiation, is transferred by its interaction with the surrounding atoms.
In the radiation zone of the Sun the temperature is a
little cooler than the core and as a result some atoms are able to remain
intact.
These intact atoms are able to absorb energy, store it for awhile, and then
later emit
that energy as new radiation. In this manner the energy that is generated in
the core is passed
from atom to atom through the radiation zone.
As an illustration, imagine standing in a crowded
gymnasium with each person holding an empty glass. There is a sink on one
end of the gym and someone at the opposite end wants a drink, but because
the gym is so crowded no one can move. The person nearest the sink can
fill their glass with water and pour it into the glass next to them. This
process could continue until the water is passed across the gym. This is
similar to the Sun's energy being passed from atom to atom until it
reaches the end of the radiation zone.
One important difference between our analogy and what takes place in the Sun
is that in the gym we would pass the water in such a way that it always moves
towards the other side. The atoms in the Sun do not do this. Infact,
there is no direct communication between one end of the radiation zone
and the other. Instead, the Sun's energy is passed randomly from atom to
atom. Sometimes it moves
outward, sometimes inward and just a often it moves side to side. It takes
over 170 thousand years for the energy released in the core of the
Sun to get out of the radiation zone!
Convection Zone
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