Assessing the Massive Young Sun Hypothesis to Solve the Warm Young Earth Puzzle

A moderately massive early Sun has been proposed to resolve the so-calledfaint early Sun paradox. We calculate the time-evolution of the solar mass thatwould be required by this hypothesis, using a simple parametrizedenergy-balance model for Earth's climate. Our calculations show that the solarmass loss rate would need to have been 2-3 orders of magnitude higher thanpresent for a time on the order of ~2 Gy. Such a mass loss history issignificantly at variance (both in timescale and in the magnitude of the massloss rates) with that inferred from astronomical observations of mass loss inyounger solar analogues. While suggestive, the astronomical data cannotcompletely rule out the possibility that the Sun had the required mass losshistory; therefore, we also examine the effects of the hypothetical historicalsolar mass loss on orbital dynamics in the solar system, with a view toidentifying additional tests of the hypothesis. Planetary and satellite orbitsprovide a few tests, but these are weak or non-unique.Comment: 19 pages, 4 figures, 1 table; submitted to ApJ on Dec. 8, 200