Assessing the massive young Sun hypothesis to solve the warm young Earth puzzle

Yet more from this morning's astro-ph:

astro-ph/0612321
Title: Assessing the massive young Sun hypothesis to solve the
warm young Earth puzzle
Authors: David A. Minton, Renu Malhotra
Comments: 19 pages, 4 figures, 1 table; submitted to ApJ on
Dec. 8, 2006

A moderately massive early Sun has been proposed to resolve the
so-called faint early Sun paradox. We calculate the time-evolution of
the solar mass that would be required by this hypothesis, using a
simple parametrized energy-balance model for Earth's climate. Our
calculations show that the solar mass loss rate would need to have
been 2-3 orders of magnitude higher than present for a time on the
order of ~2 Gy. Such a mass loss history is significantly at variance
(both in timescale and in the magnitude of the mass loss rates) with
that inferred from astronomical observations of mass loss in younger
solar analogues. While suggestive, the astronomical data cannot
completely rule out the possibility that the Sun had the required mass
loss history; therefore, we also examine the effects of the
hypothetical historical solar mass loss on orbital dynamics in the
solar system, with a view to identifying additional tests of the
hypothesis. We find that ratios of planetary orbital spacings remain
unchanged, relative locations of planetary mean motion and secular
resonances remain unchanged, but resonance widths and the sizes of the
Hill spheres of all planets increase as the Sun loses mass. The
populations and dynamics of objects near resonances with the planets
as well as those of distant irregular satellites of the giant planets
may contain the signature of a more massive early Sun. Planetary and
satellite orbits provide a few test, but these are weak or non-unique.

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