Is There a Planet 9?

Before I start, I should remind everyone of the solar system yardstick: the unit of measurement called the Astronomical Unit, or AU, which is the distance from Earth to the Sun. I am also going to define a mass unit, the emu, which is the mass of the Earth, or Earth mass unit.

As you know, there are eight planets, with the furthest out being Neptune, which is 30 AU from the Sun. Now the odd thing is, Neptune is a giant of 17 emu, Uranus is only about 14.5 emu, so there is more to Neptune than Uranus, even though it is about 12 AU further out. So, the obvious question is, why do the planets stop at Neptune, and that question can be coupled with, “Do they?” The first person to be convinced there had to be at least one more was Percival Lowell, he of Martian canal fame, and he built himself a telescope and searched but failed to find it. The justification was that Neptune’s orbit appeared to be perturbed by something. That was quite reasonable as Neptune had been found by perturbations in Uranus’ orbit that were explained by Neptune. So the search was on. Lowell calculated the approximate position of the ninth planet, and using Lowell’s telescope, Clyde Tombaugh discovered what he thought was planet 9.  Oddly, this was announced on the anniversary of Lowell’s birthday, Lowell now being dead. As it happened, this was an accidental coincidence. Pluto is far too small to affect Neptune, and it turns out Neptune’s orbit did not have the errors everyone thought it did – another mistake. Further, Neptune, as with the other planets has an almost circular obit but Pluto’s is highly elliptical, spending some time inside Neptune’s orbit and sometimes as far away as 49 AU from the Sun. Pluto is not the only modest object out there: besides a lot of smaller objects there is Quaoar (about half Pluto’s size) and Eris (about Pluto’s size). There is also Sedna, (about 40% Pluto’s size) that has an elliptical orbit that varies the distance to the sun from 76 AU to 900 AU.

This raises a number of questions. Why did planets stop at 30 AU here? Why is there no planet between Uranus and Neptune? We know HR 8977 has four giants like ours, and the Neptune equivalent is about 68 AU from the star, and that Neptune-equivalent is about 6 times the mass of Jupiter. The “Grand Tack” mechanism explains our system by arguing that cores can only grow by major bodies accreting what are called planetesimals, which are bodies about the size of asteroids, and cores cannot grow further out than Saturn. In this mechanism, Neptune and Uranus formed near Saturn and were thrown outwards and lifted by throwing a mass of planetesimals inwards, the “throwing”: being due to gravitational interactions. To do this there had to be a sufficient mass of planetesimals, which gets back to the question, why did they stop at 30 AU?

One of the advocates for Planet 9 argued that Planet 9, which was supposed to have a highly elliptical orbit itself, caused the elliptical orbits of Sedna and some other objects. However, this has also been argued to be due to an accidental selection of a small number of objects, and there are others that don’t fit. One possible cause of an elliptical orbit could be a close encounter with another star. This does happen. In 1.4 million years Gliese 710, which is about half the mass of the Sun, will be about 10,000 AU from the Sun, and being that close, it could well perturb orbits of bodies like Sedna.

Is there any reason to believe a planet 9 could be there? As it happens, the exoplanets encylopaedia lists several at distances greater that 100 AU, and in some case several thousand AU. That we see them is because they are much larger than Jupiter, and they have either been in a good configuration for gravitational lensing or they are very young. If they are very young, the release of gravitational energy raises them to temperatures where they emit yellow-white light. When they get older, they will fade away and if there were such a planet in our system, by now it would have to be seen by reflected light. Since objects at such great distances move relatively slowly they might be seen but not recognized as planets, and, of course, studies that are looking for something else usually encompass a wide sky, which is not suitable for planet searching.For me, there is another reason why there might be such a planet. In my ebook, “Planetary Formation and Biogenesis” I outline a mechanism by which the giants form, which is similar to that of forming a snowball: if you press ices/snow together and it is suitably close to its melting point, it melt-fuses, so I predict the cores will form from ices known to be in space: Jupiter – water; Saturn – methanol/ammonia/water; Uranus – methane/argon; Neptune – carbon monoxide/nitrogen. If you assume Jupiter formed at the water ice temperature, the other giants are in the correct place to within an AU or so. However, there is one further ice not mentioned: neon. If it accreted a core then it would be somewhere greater than 100 AU.  I cannot be specific because the melting point of neon is so low that a number of other minor and ignorable effects are now significant, and cannot be ignored. So I am hoping there is such a planet there.

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That Was 2017, That Was

With 2017 coming to a close, I can’t resist the urge to look back and see what happened from my point of view. I had plenty of time to contemplate because the first seven months were largely spent getting over various surgery. I had thought the recovery periods would be good for creativity. With nothing else to do, I could write and advance some of my theoretical work, but it did not work but like that. What I found was that painkillers also seemed to kill originality. However, I did manage one e-novel through the year (The Manganese Dilemma), which is about hacking, Russians and espionage. That was obviously initially inspired by the claims of Russian hacking in the Trump election, but I left that alone. It was clearly better to invent my own scenario than to go down that turgid path. Even though that is designed essentially as just a thriller, I did manage to insert a little scientific thinking into the background, and hopefully the interested potential reader will guess that from the “manganese” in the title.

On the space front, I am sort of pleased to report that there was nothing that contradicted my theory of planetary formation found in the literature, but of course that may be because there is a certain plasticity in it. The information on Pluto, apart from the images and the signs of geological action, were well in accord with what I had written, but that is not exactly a triumph because apart from those images, there was surprisingly little new information. Some of which might have previously been considered “probable” was confirmed, and details added, but that was all. The number of planets around TRAPPIST 1 was a little surprising, and there is limited evidence that some of them are indeed rocky. The theory I expounded would not predict that many, however the theory depended on temperatures, and for simplicity and generality, it considered the star as a point. That will work for system like ours, where the gravitational heating is the major source of heat during primary stellar accretion, and radiation for the star is most likely to be scattered by the intervening gas. Thus closer to our star than Mercury, much of the material, and even silicates, had reached temperatures where it formed a gas. That would not happen around a red dwarf because the gravitational heating necessary to do that is very near the surface of the star (because there is so much less falling more slowly into a far smaller gravitational field) so now the heat from the star becomes more relevant. My guess is the outer rocky planets here are made the same way our asteroids were, but with lower orbital velocities and slower infall, there was more time for them to grow, which is why they are bigger. The inner ones may even have formed closer to the star, and then moved out due to tidal interactions.

The more interesting question for me is, do any of these rocky planets in the habitable zone have an atmosphere? If so, what are the gases? I am reasonably certain I am not the only one waiting to get clues on this.

On another personal level, as some might know, I have published an ebook (Guidance Waves) that offers an alternative interpretation of quantum mechanics that, like de Broglie and Bohm, assumes there is a wave, but there are two major differences, one of which is that the wave transmits energy (which is what all other waves do). The wave still reflects probability, because energy density is proportional to mass density, but it is not the cause. The advantage of this is that for the stationary state, such as in molecules, that the wave transmits energy means the bond properties of molecules should be able to be represented as stationary waves, and this greatly simplifies the calculations. The good news is, I have made what I consider good progress on expanding the concept to more complicated molecules than outlined in Guidance Waves and I expect to archive this sometime next year.

Apart from that, my view of the world scene has not got more optimistic. The US seems determined to try to tear itself apart, at least politically. ISIS has had severe defeats, which is good, but the political futures of the mid-east still remains unclear, and there is still plenty of room for that part of the world to fracture itself again. As far as global warming goes, the politicians have set ambitious goals for 2050, but have done nothing significant up to the end of 2017. A thirty-year target is silly, because it leaves the politicians with twenty years to do nothing, and then it would be too late anyway.

So this will be my last post for 2017, and because this is approaching the holiday season in New Zealand, I shall have a small holiday, and resume half-way through January. In the meantime, I wish all my readers a very Merry Christmas, and a prosperous and healthy 2018.

What have we learned about Pluto so far?

New Horizons has caught our attention, or at least it should have. Pluto is about 5,874,000,000 km from the sun, or 39.26 times as far from the sun as Earth is. The reason I say “about” is that the orbit is eccentric, and sometimes is closer to the sun than Neptune is, but it is an orbital resonance with Neptune, so it will never collide with it (unless something else disturbs the resonance). The space craft flew by Pluto at about 50,000 km, so think of the triumph of getting that accuracy. The cameras can see objects down to about a kilometer in size.

Pluto is actually smaller than our moon, and has only 18% of our moon’s mass, but because it is about 1/3 ice, it has more water than Earth. When Pluto gets closer to the sun, it has a weak atmosphere of nitrogen, and probably some carbon monoxide and maybe methane and argon. As it gets further from the sun, these gases snow out. The surface temperature varies, but is in the order of minus 230 degrees Centigrade. That much we knew.

Pluto has an interesting history, in that it was predicted by Percival Lowell in 1915 based on deviations found in the orbits of Neptune and Uranus. Neptune itself was discovered because the orbit of Uranus did not follow Newton’s laws exactly, but it would if there were another giant planet pulling on it. Accordingly, astronomers could predict where Neptune would be, they looked, and there it was. A triumph for physics. However, Neptune’s orbit was still not right, so Lowell predicted a further planet, calculated where it should be, and Clyde Tombaugh found it in 1930. Another triumph! Nevertheless, this shows an important fact, namely just because you can predict something that turns up, that does not mean the basis of the prediction was correct, as Pluto is far too small to account for what Lowell calculated. The discovery was a happy accident.

So, what have we discovered about Pluto? In my opinion, so far, not a lot, but that is mainly because most of the data will not come in for months. We have corrected Pluto’s size, but that is not a huge achievement. However, the images have given us a lot to think about. The one thing that has surprised us is that Pluto is geologically active, and far more so than anyone might have expected. I have seen statements that it must have been essentially resurfaced about a hundred million years ago. I am not too sure about that, as it is based on crater count, and I doubt anyone has any good data on collisions that far out. Furthermore, if the bodies out there are largely icy, and Pluto’s surface is mainly ice, then because collision velocities will be a lot slower out there, it is possible that collisions will not excavate a crater, but rather the energy will melt the ice, it will flow, then re-freeze, thus not forming a crater. Nevertheless, the mountains, canyons, and the flat areas are indicative that there has been significant internal heat. That could come from a number of sources, such as radioactive decay, collisions, one of which may have formed the moon system, and possibly even a little chemistry.

The heat may not have to be intense if it is uneven, because it would volatalise gases such as nitrogen, and that would create a lot of internal stress. Another form of internal stress may come from freezing water. If the outer layers are largely free of rock, that having sunk to the core, then because water expands a little on freezing, that “little” will be magnified into quite a change of length over the circumference even of a dwarf planet, and with nowhere to go, there could be considerable additional warpage. That is unlikely to account for all the mountains, etc, but it may add to the cause and magnify it.

What do we think we know about Pluto? Try this link: http://www.forbes.com/sites/fayeflam/2015/07/21/the-weirdest-reason-pluto-didnt-become-a-real-planet/
Here, they argue Pluto grew in the region of Jupiter/Saturn, and with Uranus and Neptune, were thrown out into the outer solar system, where there is not enough material to grow. I don’t believe that, because I don’t believe the standard theory of planetary formation, which starts off by assuming that the dust accretes into planetesimals by some unknown mechanism, and these collide to form larger objects, and finally, planets. The reason the outer giants had to start in the Jupiter/Saturn region is that collisional probabilities are too low to get giants much further out under this mechanism. In my “Planetary Formation and Biogenesis”, I argue the first step is actually based on physical chemistry, essentially the same mechanism as forming a snowball, and the planets form at temperatiures where the various ices assist. Ion this theory, Pluto, and the other Kuiper Belt objects formed by the same mechanism that Neptune formed, but because the temperatures were starting to get too low, accretion was slow, but because they were far enough away, they did not get “collected” by Neptune.

So, will we find out more? Basically, we now have to wait for more data, but in the meantime we should congratulate NASA on a truly great achievement. They still have “the right stuff”.