Abstract: We revisit the distant future of the Sun and the solar system, based onstellar models computed with a thoroughly tested evolution code. For the solargiant stages, mass-loss by the cool (but not dust-driven) wind is considered indetail. Using the new and well-calibrated mass-loss formula of Schroder & Cuntz(2005, 2007), we find that the mass lost by the Sun as an RGB giant (0.332M_Sun, 7.59 Gy from now) potentially gives planet Earth a significant orbitalexpansion, inversely proportional to the remaining solar mass.
According to these solar evolution models, the closest encounter of planetEarth with the solar cool giant photosphere will occur during the tip-RGBphase. During this critical episode, for each time-step of the evolution model,we consider the loss of orbital angular momentum suffered by planet Earth fromtidal interaction with the giant Sun, as well as dynamical drag in the lowerchromosphere. We find that planet Earth will not be able to escape engulfment,despite the positive effect of solar mass-loss. In order to survive the solartip-RGB phase, any hypothetical planet would require a present-day minimumorbital radius of about 1.15 AU.
Furthermore, our solar evolution models with detailed mass-loss descriptionpredict that the resulting tip-AGB giant will not reach its tip-RGB size. Themain reason is the more significant amount of mass lost already in the RGBphase of the Sun. Hence, the tip-AGB luminosity will come short of driving afinal, dust-driven superwind, and there will be no regular solar planetarynebula (PN). But a last thermal pulse may produce a circumstellar (CS) shellsimilar to, but rather smaller than, that of the peculiar PN IC 2149 with anestimated total CS shell mass of just a few hundredths of a solar mass.
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