[ExI] Earth is doomed. Mars is OK, though.

[Amara Graps]

http://arxiv.org/abs/0801.4031

Distant future of the Sun and Earth revisited
Authors: Klaus-Peter Schroder, Robert C. Smith
(Submitted on 25 Jan 2008)

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 Schroder & Cuntz (2005, 2007), we
find that the mass lost by the Sun as an RGB giant (0.332 M_Sun, 7.59 Gy
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. 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.

Furthermore, our solar evolution models with detailed mass-loss
description predict that the resulting tip-AGB giant will not reach its
tip-RGB size. 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). But a last thermal pulse
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.

Comments:	MNRAS 2008, in print (accepted Jan. 23rd, 2008)
Subjects:	Astrophysics (astro-ph)
Cite as:	arXiv:0801.4031v1 [astro-ph]
Submission history
From: Klaus-Peter Schr\"oder [view email]
[v1] Fri, 25 Jan 2008 21:13:29 GMT (34kb)
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Amara Graps, PhD      www.amara.com
Research Scientist, Southwest Research Institute (SwRI), Boulder, Colorado