PX282 - A7 - inside a star
- photons are released from nuclear-energy production, which do not get out easily
- these photons are absorbed by material progressively further from the core in a random 'walk'
- energy is transferred by photons, convection, atom collisions, magnetic field
- the photons seen arise from near the 'surface', from material in thermal equilibrium
- emission from a gas in thermal equilibrium can be approximated by black body radiation, which follows planck's law:

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key observations:
- hotter objects have a higher peak, ie. they give off more energy
- total energy under the curve is:
where,
is the stefan-botzmann constant - at peak
, ie: at , the wien's displacement law:
- as
,
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consider the units of