Model for the inside of the Sun
It isn't easy to understand the interior of the Sun since
we lack direct observations (with an important exception,
to be discussed later).
We use a theoretical model. Some ingredients are
- gravity: the mass of matter pulls the gas in.
- pressure: a gas has pressure, which pushes out and
resists gravity.
- pressure is higher if temperature is higher.
- pressure is higher if density is higher.
- energy production (from fusion, to be discussed later)
- energy production is higher if temperature is higher.
- energy production is higher if density is higher.
- energy transport
- radiation (photons).
- convection.
According to the theoretical models, the density and tempreature
are low at the photosphere and increase toward the center.
- density.
- 0.1 kg/m at photosphere
- 150 x 103 kg/m3 at center.
- temperature
- 6 x 103 K at photosphere.
- 15 x 106 K at center.
According to the theoretical models, the energy transport is
by photon radiation in the inside, by convection in the outer
1/4 of the Sun.
- Radiation
- the gas just sits there
- the particles of the hot gas emit photons
- the photons go a short distance and are absorbed.
- since it is hotter on the lower layers, the lower layers
are emitting more photons than the upper layers.
- therefore more photons go up than down.
- the photons transport energy toward the photosphere
- Convection
- gas on inside layers is warmed and rises.
- then it cools and sinks.
- the moving gas transports energy toward the photosphere.
Davison E. Soper, Institute of Theoretical Science,
University of Oregon, Eugene OR 97403 USA
soper@bovine.uoregon.edu