Variation of the Gravitational Constant and the Evolution of the Sun.
Abstract
Evolutionary model sequences have been computed for the Sun under various assumptions for the variation of the gravitational constant G. For these computations G was taken to vary to the reciprocal of the power n of the time. For the age of the Universe, T, values ranging from 15 billion years were used. It was assumed that 4.5 billion years ago the Sun was in its initial mainuence state. It was found that a mild variation of G, corresponding to n = 0.2, produces no difficulty the representation of the observed Sun as the end product of an evolution starting with the initial in-sequence state and lasting for 4.5 billion years. In contrast, a strong variation of G, corresponding =1.0, permits a satisfactory representation of the present Sun only if the age of the Universe is ut 15 billion years or more. This limitation arises from the circumstance that with a shorter age of Universe the initial main-sequence state of the sun falls relatively earlier in the history of the Universe a G, under the present assumptions, was still rather high; this causes so large an initial luminosity .he Sun as to lead to an exhaustion of the hydrogen in the solar core and an evolution off the main uence before 4.5 billion years would have elapsed.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1964
- DOI:
- 10.1086/147787
- Bibcode:
- 1964ApJ...139..587P