Is science sometimes in danger of getting tunnel vision? Recently published ebook author, Ian Miller, looks at other possible theories arising from data that we think we understand. Can looking problems in a different light give scientists a different perspective?

November-December Planetary Update

My alternative explanations for planetary formation survived a further two months. The reason for not giving a November update was not that I was hiding something, but there was word that a "huge announcement" would be made from the Curiosity team on December 5 so I waited. Could this fulfill one of my predictions? Er, no! The announcement was a bit of a squib: the last bit of equipment was working. Yes, this is a minor miracle, but it says nothing about planetary formation.
Obviously, a good number of papers were published, but very few had anything relevant to say about this theory. One of the more interesting came from Tobin et al., (Nature 492: 83-85). The protostar L1527 IRS has about 0.2 solar masses, while it is surrounded by a rotationally supported disk containing at least seven Jupiter masses, and further surrounded by an envelope containing about 1 solar mass. This is obviously a star in the early stages of formation, and as far as can be seen, it follows standard theory quite nicely. If we wait for about 3 million years we might see newly formed planets!
A paper by Crida and Charnoz (Science 338: 1196 – 1199) proposes that satellites form from massive rings around planets. A case is made that such rings form, then spread out beyond the Roche limit, accrete into larger bodies, and are moved out by tidal forces. It is not entirely clear, at least to me, how this works with gas accreting inwards, as gas drag should drag bodies inwards. The model is claimed to give good agreement with Neptune's inner minor satellites, the Uranian system, and Saturn's inner system. The Jovian system does not fit, and Titan is not really a good fit. One problem is that such rings must be extremely massive. The proposal differs from what I proposed, although my compositional proposal might still explain the rings, if they existed.
For those wondering how my theory differs from standard theory, the latter is essentially purely physical, with accretion being due to gravity and driven by gas flows, turbulence, etc that lead to collisions. I agree that these are important, and the main drivers once a certain size is reached, however standard theory cannot explain how the starting position, a distribution of planetesimals, form, because bodies up to tens of kilometers in size have negligible gravity, and collisions do not lead to binding strength. My major difference is that the initial stages are driven by chemistry, and our system is typical of such a system where the star blows out the disk within 1 My after forming. If this does not happen, planets keep accreting, and now become gravitationally unstable, which leads to a variety of different, smaller system types. By being driven by chemistry, the governing variable during the initial accretion stages is temperature.
Just before posting this, a new system was claimed: Tau ceti is claimed to have planets with semimajor axes at 0.1, 0.195, 0.37, 0.55 and 1.35 A.U.  I made approximate predictions for the outer part of this system, and the outcome is mixed. In my theory, the rocky planets are governed by two temperature profiles, the initial accretion, and that prior to the final removal of disk material, while the outer planets are primarily determined by the primary temperature distribution. If we interpret the planet at 1.35 A.U. as the accretor due to water ice (i.e. the Jupiter equivalent, irrespective of size), then the outer planets are about twice as close to the star as I suggested, which could arise if Tau Ceti accreted more slowly than our star, or because Tau Ceti has a lower metallicity, the accretion disk may have radiated heat better, by being somewhat more transparent. If so, and if these distances are real (see caveat below) there will be three further planets at about 2.1 A.U, 4.7 A.U., and 7.8 A.U. The one at 4.7 A.U. would be the smallest, while the one at 2.1 A.U would have formed an atmosphere similar to that of Titan. (I had predicted the second outermost one would have an atmosphere of nitrogen, if it were big enough to have an atmosphere, but because the planet is twice as close to the star, it too might have volatile methane.) The inner planets are further from the star than simple proportion, as would be expected because the second temperature profile is significantly due to stellar radiation. So is that confirmation or falsification? It may be neither, because a caveat must be noted: These planets are small; the so-called Jupiter equivalent is only 2% that of our Jupiter (although I predicted they would be small, due to the lower metallicity) and were detected at the very limit of stellar wobble. They may not be real, or may not be quite as reported.
Finally, I wish you all to enjoy the festive season. This will be my last blog until next year, when I shall return with some postscripts to my PhD project.
Posted by Ian Miller on Dec 21, 2012 10:13 PM Europe/London

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