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?

Planetary Formation Update – February - March

Only two papers qualified for inclusion in two months, so perhaps I should remind readers that the criterion for qualification is that the paper was relevant to my theory of planetary formation, which differs from the standard one in that the reason matter accretes is because of some chemical feature, including physical chemistry, whereas standard theory just assumes planetesimals accrete by some unknown mechanism. The consequences of my approach is that because what happens with chemistry is highly temperature dependent, the various bodies of the solar system should fall into different groups (centred around a planet) with properties of the group if they are small enough. (Gas giants simply collect everything, but their moons qualify.)
So with that in mind, there were two announcements that I found surprisingly satisfying. The first was the announcement of the discovery of a "clump" of carbon monoxide gas of about 0.09% the mass of the moon in the debris disk of Beta Pictoris. (Dent et al, Science 343: 1490 – 1492) This gas clump was argued to be a region of enhanced collisions of many objects, the collisions there being a result of mean motion resonance with an unseen giant planet that is greater than 10 earth masses, or from the remnants of a collision of Mars-mass planets. There is tentative evidence to favour the first interpretation. The authors suggested a giant planet at 60 A.U would provide a 2:1 resonance.
Why do I find that of interest? Well, based on dust distributions and my theory, I considered the planets to be as follows: Uranus equivalent at 68 A.U., Neptune equivalent at 114 A.U., with resonances at 82 A.U. 3:4 with the Uranus equivalent and 3:2 resonance with the Neptune equivalent. The bodies causing the collisions should have originated from around Neptune or from the equivalent of a Kuiper Belt, assuming similar dynamics to our system. Now, the reason I find this important is because only objects from this distance are cold enough to accrete carbon monoxide in the ices that make up the core. (Jupiter has carbon monoxide, but Jupiter accreted most of its gas gravitationally from the disk, and thus accreted all available gas.) My argument is that it is the presence of the carbon monoxide (and nitrogen) that enabled objects that would cause Neptune and Kuiper belt objects to accrete. As an aside, this explains why Neptune is bigger and denser than Uranus: carbon monoxide and nitrogen were far more prevalent than methane and argon, the gases that started Uranian accretion. Accordingly Neptune will accrete more solids, although once it gets big enough, Uranus will accrete gases faster because of the higher gas density. However, back to the issue. The gravitational field of the Neptune equivalent will stir up objects reasonably close to Neptune, and lead to such collisions. There should be other planets there (and one is known somewhat closer to the star) but there is no corresponding "clump" of carbon monoxide. That does not prove anything, but at least it is in accord with what my theory would predict.
The second announcement was that a second Sedna-like object, 2012VP113 with a perihelion distance of 80 A.U. has been found (Trujillo and Sheppard, Nature 507: 471 – 474). Such objects are sufficiently far away that they do not interact gravitationally with any other known planet. One interesting feature of these is that each has a relatively high eccentricity (VP  0.7, Sedna 0.86), and such eccentricities would usually be interpreted as arising from an acute gravitational interaction with something else, There appear to be no objects between 50 and 75 A.U., at least of any size, which raises the question, how do such bodies form. One possibility raised was gravitational interactions with a super earth, possibly as far away as 250 A.U.
How does that affect my theory of giant planet formation? That is difficult to say. The theory assumes that the ice planet cores accrete by ices sticking together when they strike each other due to an icy constituent melting and refreezing. (Vapour pressure is not relevant because the gases are occluded in water ice channels. Such ices have been made and are stable at very low pressures.) If so, my theory allows for another ice planet, or at least icy bodies, provided neon is the brazing component. The problem then is, where would the planet be? The variables are, the temperature below the melting point where collisions are effective, the heating function of the accretion disk, the orbital velocities, and the initial temperature. By simple extrapolation of the temperature relationship used for the other giant planets, the answer is 95 A.U., but the problem then is that this assumes that the initial gas temperature was zero. If something is proportional to A – B , if B is only at worst a few per cent of A, then given all the other uncertainties, errors in B can be ignored, but if B is approaching A, it is really serious. When we get down to neon, such failures in the approximations will make a big difference. There is a test: the bodies such as Sedna should contain neon below the surface, if I am correct, but how to find out?
Posted by Ian Miller on Apr 13, 2014 11:36 PM Europe/London

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