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Summary
We have learned a star to be a radiating gaseous sphere, made predominantly of hydrogen and helium. Radiation may be regarded as a photon gas, each ‘particle’ carrying a quantum of energy hν, proportional to the frequency ν of the associated electromagnetic wave, and a momentum hν/c, where h is Planck's constant and c is the speed of light. This mixture of gases that makes up a star is governed by frequent collisions between its particles, ions, electrons and photons alike. This is how Sir Arthur Eddington describes The Inside of a Star:
… Try to picture the tumult! Dishevelled atoms tear along at 50 miles a second with only a few tatters left of their elaborate cloaks of electrons torn from them in the scrimmage. The lost electrons are speeding a hundred times faster to find new resting-places. Look out! there is nearly a collision as an electron approaches an atomic nucleus; but putting on speed it sweeps round it in a sharp curve. A thousand narrow shaves happen to the electron in 10−10 of a second; sometimes there is a slide-slip at the curve, but the electron still goes on with increased or decreased energy. Then comes a worse slip than usual; the electron is fairly caught and attached to an atom, and its career of freedom is at an end. But only for an instant. […]
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- Publisher: Cambridge University PressPrint publication year: 2009