THE SUN
Hydrostatic equilibrium
The source of the sun’s energy is
NUCLEAR FUSION
H + H → He
In this process…
A small amount of
(nuclear) mass is
converted to energy.
Proton-proton chain
Specifically, gamma rays
High energy,
short wavelength
When a gamma ray photon collides
with an H or He nucleus
It is ABSORBED
then
RE-EMITTED
As this happens over and over,
The photon eventually photon
loses some of its energy and
changes to a different form of EM energy.
(The nuclei of atoms can absorb energy (from a gamma ray or a neutron, for instance), which
produces an unstable nucleus which can then go to a lower energy by emitting a gamma ray, or
by splitting (fission) in the case of a few atoms.)
By the time it reaches
the surface which may
take 15 million years) it
may have been
converted to….
Visible light….
Longer wavelength,
lower frequency
WHY SO LONG?
The sun’s great
mass/gravity squeeze
the gas below the
surface so the particles
are very close together.
According to Gay-Lussac’sLaw
TEMEPERATURE AND
PRESSURE ARE
DIRECTLY RELATED
SO….
Gay-Lussac’s Law
More squeezing, the gas gets hotter
The hotter the gas
gets, the more it
wants to spread out
If it can’t spread out
The pressure increases.
More pressure, more higher
temperature--
The sun’s core has a
high temperature—15
million Kelvins
The higher the temperature
The greater the gas
pressure pushing
OUT from the core.
It is this pressure
THAT BALANCES THE
GRAVITY OF THE
SUN
THE BALANCE BETWEEN GAS
PRESSURE AND GRAVITY IS CALLED
HYDROSTATIC
EQUILIBRIUM