Abstract
Take another look at Fig. 3.1. Chap. 3 was largely concerned with the material body shown in the diagram, while this chapter is largely concerned with the flow of radiation, the second critical component in Eddington’s two-part star model. Recall that the material body is described according to the interactions between the protons, electrons and ions that make up the material mass of a star. In contrast, the radiative body is described according to the passage of radiation and energy through the material body. Neither component can exist for long without the other, and as we have seen, the material body of a star would collapse on a timescale of hours if its interior was not hot and supported by a pressure gradient. The radiative component would dissipate even more rapidly if it did not interact with a star’s material body. Traveling at the speed of light, a photon would take just 2 s to cross the Sun’s radius, and yet for all its haste, the passage of radiation through a star is a tortuous affair, and the escape time is stretched out to many hundreds of thousands of years. As Arthur Eddington descriptively put it in his 1920 address to the British Association, ‘The star is like a sieve, which can retain them [photons] only temporarily; they are turned aside, scattered, absorbed for a moment, and flung out again in a new direction. An element of energy may thread the maze for hundreds of years [this is an underestimate; see below] before it attains the freedom of outer space’.
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Notes
- 1.
Wien’s law [equation (1.12)] dictates that between the center and surface of the Sun, the wavelength λmax will increase from 2×10−10 m to 5×10−7 m—an increase by a factor of 2500.
- 2.
As always there are caveats. It transpires that multiple solutions to the equations of stellar structure can be engineered when special conditions are made to apply. Technically, this constitutes a numerical proof that the VR theorem is, in fact, not always true!
- 3.
See also the research paper, Very Massive Stars: evolution with mass loss by Jaime Klapp (Astrophysics and Space Science, 93, 313–345, 1983). In this paper, stars in the mass range from 500 to 10,000 M⊙ are studied. Such stellar models are of interest from a cosmological viewpoint, since the very first Population III stars are thought to form with such very high masses.
- 4.
Attention is also drawn to the first part of the research paper: On the Theory of Evolution of Completely Mixed Stars with Mass Loss, by Richard Stothers [Monthly Notices of the Royal Astronomical Society (1966), 131, 253–362].
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Beech, M. (2019). From the Inside Out. In: Introducing the Stars. Undergraduate Lecture Notes in Physics. Springer, Cham. https://doi.org/10.1007/978-3-030-11704-7_4
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