Monday, July 23, 2012

New planets keep coming in to replace the ones falling into the star



Does a flow of hot Jupiters explain how they actually are being found in the final fraction of their lives? 

I suggest that there is a flow of "new planets" that keep coming into the star, to replace the ones that have already fallen into the star. I am preparing evidence that an ongoing resupply of distant giant planets explains several mysteries of the distribution of exoplanets: why are some of these planets being found only a remarkably short time before they are destroyed by the star, why are so many giant planets inflated, and what causes the pile up of Jupiter sized planets. I extend the recent work of others (such as the2012 work by the group including Aristotle Socrates and Subo Dong) who are finding that there should be a “flow” or “current” of high eccentricity giant planets bringing outer planets into the inner solar system, where I propose they continue to migrate towards the star. I propose that such an ongoing movement of planets is sufficient to not have to invoke low tidal dissipation on the star as an explanation for why these planets could be found in such short period orbits. While others have tried to say that tidal friction is so low that these planets really can last for a long fraction of a star’s lifetime, I explain that these planets really are being found in the last fraction of their lives. It may be a special time in the lifetime of these individual planets, but I suggest that the flow of planets is large enough that at anytime observers would find some planets this close to their stars. This would also make it easier to explain the high number of inflated planets as being a result of heat recent migration, since I do not require that inflated planets either maintain or not lose their heat for the long periods required by the “slow migration” model. I support the suggestions of others that the pileup of planets results from the region between where high eccentricity orbits get damped out, and where tides from the star starts to cause these planets to migrate in again.



I have also found a pattern that suggests that the migration of planets to short periods is correlated with planets having already fallen into the star, based on a correlation of the fraction of iron (Fe) in the star with the eccentricity of planets, after some consideration of other parameters, especially the size of the planets. This suggests that the flow of planets is not restricted to giant planets, but perhaps only the giant planets predominately make the ordered transition from high eccentricity orbit to hot Jupiter. Perhaps smaller planets suffer more violent fates, with a large fraction having orbits badly disrupted such that many are sent into being consumed by the star, leaving what has been called the “pollution” of the higher level of Fe that has long been known to be correlated with finding giant exoplanets. What I find especially remarkable is that there is the appearance, albeit with small statistics, that planets more massive than twice that of Neptune that are further from the star than hot Jupiters that have very high eccentricity are correlated with a rising fraction of Fe. This suggests that the stars in systems with these eccentric planets might have been polluted more recently than the host stars of hot Jupiters, which have thus had more time to remix this pollution into the star.



What this suggests is that solar systems are far more chaotic than we ever thought. Though new papers are still being presented that seek to describe planet system architectures by what happens at planet formation, we may find that much of the planet system structure that we see is still being changed by ongoing dynamical processes.