Distant future of the Sun and Earth revisited

Schroeder, K.-P. and Smith, Robert Connon (2008) Distant future of the Sun and Earth revisited. Monthly Notices of the Royal Astronomical Society, 386 (1). pp. 155-163. ISSN 0035-8711

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Abstract

We revisit the distant future of the Sun and the Solar system, based on stellar models computed with a thoroughly tested evolution code. For the solar giant stages, mass loss by the cool (but not dust-driven) wind is considered in detail. Using the new and well-calibrated mass-loss formula of Schroeder & Cuntz, we find that the mass lost by the Sun as a red giant branch (RGB) giant (0.332 Msun, 7.59 Gyr from now) potentially gives planet Earth a significant orbital expansion, inversely proportional to the remaining solar mass. According to these solar evolution models, the closest encounter of planet Earth with the solar cool giant photosphere will occur during the tip-RGB phase. During this critical episode, for each time-step of the evolution model, we consider the loss of orbital angular momentum suffered by planet Earth from tidal interaction with the giant Sun, as well as dynamical drag in the lower chromosphere. As a result of this, 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 solar tip-RGB phase, any hypothetical planet would require a present-day minimum orbital radius of about 1.15 au. The latter result may help to estimate the chances of finding planets around white dwarfs. Furthermore, our solar evolution models with detailed mass-loss description predict that the resulting tip-AGB (asymptotic giant branch) giant will not reach its tip-RGB size. Compared to other solar evolution models, the main reason is the more significant amount of mass lost already in the RGB phase of the Sun. Hence, the tip-AGB luminosity will come short of driving a final, dust-driven superwind, and there will be no regular solar planetary nebula (PN). The tip-AGB is marked by a last thermal pulse, and the final mass loss of the giant may produce a circumstellar (CS) shell similar to, but rather smaller than, that of the peculiar PN IC 2149 with an estimated total CS shell mass of just a few hundredths of a solar mass.

Item Type: Article
Additional Information: The uploaded file is the accepted version before proof corrections, and can also be found on the astro-ph archive at http://arxiv.org/abs/0801.4031v1
Keywords: Key words: Sun: evolution – solar–terrestrial relations – stars: evolution – stars: mass-loss – supergiants – white dwarfs.
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy
Depositing User: Robert Smith
Date Deposited: 18 Jul 2008
Last Modified: 06 Mar 2017 02:24
URI: http://sro.sussex.ac.uk/id/eprint/1800

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