An attempt to interpret the relative abundances of the elements and their isotopes

Chandrasekhar, S. ; Henrich, Louis R. (1942) An attempt to interpret the relative abundances of the elements and their isotopes Astrophysical Journal, 95 . pp. 288-298. ISSN 0004-637X

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In tbis paper an attempt is made to derive some information concerning the prestellar stage at wbich the elements are supposed to have been formed. By using first the relative abundances of the isotopes of a single element (e.g., 0, Ne, Mg, Si, and S), it is shown that a temperature of the order of a few billion degrees is indicated. The equilibrium between the fundamental nuclear particles (protons, neutrons, α-particles, electrons, and positrons) at temperatures ranging from 5 to 10 billion degrees is then studied to establish the relative concentrations of protons and neutrons as a function of the temperature. Tbis relation is then used to compute theoretical mass-abundance-curves under different physical conditions. From such calculations it is concluded that under the physical conditions specified by T=8×109 degrees and ρ= 107 gm/cm3 the theoretical mass-abundance-curve from oxygen to sulphur agrees fairly satisfactorily with the known abundance-curve according to V. M. Goldschmidt (Fig. 2). An important feature of the nuclear mixture considered is that hydrogen and helium are the two most abundant constituents, wbich is in agreement with known facts. However, the conditions indicated are seen to be quite insufficient to account for the existence of the heavy nuclei to any appreciable extent. It is, therefore, suggested that we should distinguish at least two epochs in the development of the prestellar stage. We imagine that at the earliest stages conditions of extreme temperatures and densities prevailed at wbich the heavier nuclei could have been formed. As the matter cooled to lower temperatures and densities, appreciable amounts (I part in 106) of the heavy elements must have been "frozen" into the mixture. At temperatures of the order of from 5×109 to 8×109 degrees and densities of the order of from 104 to 107 gm/cm3 the present known relative abundances of the elements from oxygen to sulphur may have been established.

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Source:Copyright of this article belongs to American Astronomical Society.
ID Code:70612
Deposited On:17 Nov 2011 14:20
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