webolife wrote:No, that is incorrect Daniel. If our sun without a change of mass were to expand to the size of the earth's orbit, for example, like a red giant it would cool down tremendously.
D_Archer wrote:webolife wrote:No, that is incorrect Daniel. If our sun without a change of mass were to expand to the size of the earth's orbit, for example, like a red giant it would cool down tremendously.
This is a substantion, no star was ever observed to balloon in size when it evolved into a red giant.
As per GTSM, more logical would be that if our Sun cools it would shrink in size...
Note that the evolution down the main sequence isn't a straight line — there are two humps, one at the transition from blue to yellow stars, and the other between yellow and red stars. Since the standard model doesn't address this, we should look to the CFDL model for an answer. Figure 3 shows the proposed layers within the Sun. As it continues to cool, the bulk ionization will relax, reducing the electric force between charged double-layers. This will allow the star to expand. The reduced density will relax the internal pressure, shifting the thresholds for charge separation by electron degeneracy pressure (EDP) downward. In other words, such thresholds occur at isobars, and if the pressure is relaxed, we have to go deeper to find the same isobars. The significance is that the near-surface conditions will change — the topmost positive layer will get deeper, because its bottom has shifted downward, and because its top isn't as firmly bound. The greater mean free path will yield redder photons. And note that this is a shift in frequency in addition to the shift from the reduced temperature. So a little bit of temperature difference results in a lot of reddening, and not a lot of decrease in luminosity (since that varies just with the temperature). Hence we get an explanation for the flatter stretch in the main sequence, before the yellow-to-red hump.
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