A Planet Destroyer

Probably everyone now knows that there are planets around other stars, and planet formation may very well be normal around developing stars. This, at least, takes such alien planets out of science fiction and into reality. In the standard theory of planetary formation, the assumption is that dust from the accretion disk somehow turns into planetesimals, which are objects of about asteroid size and then mutual gravity brings these together to form planets. A small industry has sprung up in the scientific community to do computerised simulations of this sort of thing, with the output of a very large number of scientific papers, which results in a number of grants to keep the industry going, lots of conferences to attend, and a strong “academic reputation”. The mere fact that nobody knows how to get to their initial position appears to be irrelevant and this is one of the things I believe is wrong with modern science. Because those who award prizes, grants, promotions, etc have no idea whether the work is right or wrong, they look for productivity. Lots of garbage usually easily defeats something novel that the establishment does not easily understand, or is prepared to give the time to try.

Initially, these simulations predicted solar systems similar to ours in that there were planets in circular orbits around their stars, although most simulations actually showed a different number of planets, usually more in the rocky planet zone. The outer zone has been strangely ignored, in part because simulations indicate that because of the greater separation of planetesimals, everything is extremely slow. The Grand Tack simulations indicate that planets cannot form further than about 10 A.U. from the star. That is actually demonstrably wrong, because giants larger than Jupiter and very much further out are observed. What some simulations have argued for is that there is planetary formation activity limited to around the ice point, where the disk was cold enough for water to form ice, and this led to Jupiter and Saturn. The idea behind the NICE model, or Grand Tack model (which is very close to being the same thing) is that Uranus and Neptune formed in this zone and moved out by throwing planetesimals inwards through gravity. However, all the models ended up with planets being in near circular motion around the star because whatever happened was more or less happening equally at all angles to some fixed background. The gas was spiralling into the star so there were models where the planets moved slightly inwards, and sometimes outwards, but with one exception there was never a directional preference. That one exception was when a star came by too close – a rather uncommon occurrence. 

Then, we started to see exoplanets, and there were three immediate problems. The first was the presence of “star-burners”; planets incredibly close to their star; so close they could not have formed there. Further, many of them were giants, and bigger than Jupiter. Models soon came out to accommodate this through density waves in the gas. On a personal level, I always found these difficult to swallow because the very earliest such models calculated the effects as minor and there were two such waves that tended to cancel out each other’s effects. That calculation was made to show why Jupiter did not move, which, for me, raises the problem, if it did not, why did others?

The next major problem was that giants started to appear in the middle of where you might expect the rocky planets to be. The obvious answer to that was, they moved in and stopped, but that begs the question, why did they stop? If we go back to the Grand Tack model, Jupiter was argued to migrate in towards Mars, and while doing so, throw a whole lot of planetesimals out, then Saturn did much the same, then for some reason Saturn turned around and began throwing planetesimals inwards, which Jupiter continued the act and moved out. One answer to our question might be that Jupiter ran out of planetesimals to throw out and stopped, although it is hard to see why. The reason Saturn began throwing planetesimals in was that Uranus and Neptune started life just beyond Saturn and moved out to where they are now by throwing planetesimals in, which fed Saturn’s and Jupiter’s outwards movement. Note that this does depend on a particular starting point, and it is not clear to me  that since planetesimals are supposed to collide and form planets, if there was an equivalent to the masses of Jupiter and Saturn, why did they not form a planet?

The final major problem was that we discovered that the great bulk of exoplanets, apart from those very close to the star, had quite significant elliptical orbits. If you draw a line through the major axis, on one side of the star the planet moves faster and closer to it than the other side. There is a directional preference. How did that come about? The answer appears to be simple. The circular orbit arises from a large number of small interactions that have no particular directional preference. Thus the planet might form from collecting a huge number of planetesimals, or a large amount of gas, and these occur more or less continuously as the planet orbits the star. The elliptical orbit occurs if there is on very big impact or interaction. What is believed to happen is when planets grow, if they get big enough their gravity alters their orbits and if they come quite close to another planet, they exchange energy and one goes outwards, usually leaving the system altogether, and the other moves towards the star, or even into the star. If it comes close enough to the star, the star’s tidal forces circularise the orbit and the planet remains close to the star, and if it is moving prograde, like our moon the tidal forces will push the planet out. Equally, if the orbit is highly elliptical, the planet might “flip”, and become circularised with a retrograde orbit. If so, eventually it is doomed because the tidal forces cause it to fall into the star.

All of which may seem somewhat speculative, but the more interesting point is we have now found evidence this happens, namely evidence that the star M67 Y2235 has ingested a “superearth”. The technique goes by the name “differential stellar spectroscopy”, and what happens is that provided you can realistically estimate what the composition should be, which can be done with reasonable confidence if stars have been formed in a cluster and can reasonably be assigned as having started from the same gas. M67 is a cluster with over 1200 known members and it is close enough that reasonable details can be obtained. Further, the stars have a metallicity (the amount of heavy elements) similar to the sun. A careful study has shown that when the stars are separated into subgroups, they all behave according to expectations, except for Y2235, which has far too high a metallicity. This enhancement corresponds to an amount of rocky planet 5.2 times the mass of the earth in the outer convective envelope. If a star swallows a planet, the impact will usually be tangential because the ingestion is a consequence of an elliptical orbit decaying through tidal interactions with the star such that the planet grazes the external region of the star a few times before its orbital energy is reduced enough for ingestion. If so, the planet should dissolve in the stellar medium and increase the metallicity of the outer envelope of the star. So, to the extent that these observations are correctly interpreted, we have the evidence that stars do ingest planets, at least sometimes.

For those who wish to go deeper, being biased I recommend my ebook “Planetary Formation and Biogenesis.” Besides showing what I think happened, it analyses over 600 scientific papers, most of which are about different aspects.

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Space News

There were two pieces of news relating to space recently. Thirty years ago we knew there were stars. Now we know there are exoplanets and over 4,000 of them have been found. Many of these are much larger than Jupiter, but that may be because the bigger they are, the easier it is to find them. There are a number of planets very close to small stars for the same reason. Around one giant planet there are claims for an exomoon, that is a satellite of a giant planet, and since the moon is about the size of Neptune, i.e.the Moon is a small giant in its own right, it too might have its satellite: an exomoonmoon. However, one piece of news is going to the other extreme: we are to be visited by an exocomet. Comet Borisov will pass by within 2 A.U. of Earth in December. It is travelling well over the escape velocity of the sun, so if you miss it in December, you miss it. This is of some interest to me because in my ebook “Planetary Formation and Biogenesis” I outlined the major means I believe were involved in the formation of our solar system, but also listed some that did not leave clear evidence in our system. One was exo-seeding, where something come in from space. As this comet will be the second “visitor” we have recorded recently, perhaps they are more common than I suspected.

What will we see? So far it is not clear because it is still too far away but it appears to be developing a coma. 2 A.U. is still not particularly close (twice the distance from the sun), so it may be difficult to see anyway, at least without a telescope. Since it is its first visit, we have no real idea how active it will be. It may be that comets become better for viewing after they have had a couple of closer encounters because from our space probes to comets in recent times it appears that most of the gas and dust that forms the tail comes from below the surface, through the equivalent of fumaroles. This comet may not have had time to form these. On the other hand, there may be a lot of relatively active material quite loosely bound to the surface. We shall have to wait and see.

The second piece of news was the discovery of water vapour in the atmosphere of K2-18b, a super-Earth that is orbiting an M3 class red dwarf that is a little under half the size of our sun. The planet is about eight times the mass of earth, and has about 2.7 times the radius. There is much speculation about whether this could mean life. If it has, with the additional gravity, it is unlikely that, if it did develop technology, it would be that interested in space exploration. So far, we know there is probably another planet in the system, but that is a star-burner. K2-18b orbits its star in 33 days, so birthdays would come round frequently, and it would receive about five per cent more solar radiation than Earth does, although coming from a red dwarf, there will be a higher fraction of infra-red light and less visible.

The determination of the water could be made because first, the star is reasonably bright so good signals can be received, second, the planet transits across the star, and third, the planet is not shrouded with clouds. What has to happen is that as the planet transits, electromagnetic radiation from the star is absorbed by any molecule at the frequency determined by the bond stretching or bending energies. The size of the planet compared with its mass is suggestive of a large atmosphere, i.e.it has probably retained some of the hydrogen and helium of the accretion disk. This conclusion does have risks because if it were primarily a water or ice world (water under sufficient pressure forms ice stable at quite high temperatures) then it would be expected to have an even greater size for the mass.

The signal was not strong, in part, from what I can make out, it was recorded in the overtone region of the water stretching frequency, which is of low intensity. Accordingly, it was not possible to look for other gases, but the hope is, when the James Webb telescope becomes available and we can look for signals in the primary thermal infrared spectrum, this planet will be a good candidate.So, what does this mean for the possibilities of life? At this stage, it is too early to tell. The mechanism for forming life as outlined in my ebook, “Planetary Formation and Biogenesis” suggests that the chances of forming life do not depend on planetary size, as long as there is sufficient size to maintain conditions suitable for life, such as an adequate atmospheric pressure, liquid water, and the right components, and it is expected that there will be an upper size, but we do not know what that will be, except again, water must be liquid at temperatures similar to ours. That would eliminate giants. However, more precise limits are more a matter of guess-work. The composition of the planet may be more important. It must be able to support fumaroles and I suspect it should have pre-separated felsic material so that it can rapidly form continents, with silica-rich water emitted, i.e.the type of water that forms silica terraces. That is because the silica acts as a template to make ribose. Ribose is important for biogenesis because something has to link the nucleobases to the phosphate chain. The nucleobases are required because they alone are the materials that form with the chemicals likely to be around, and they alone form multiple hydrogen bonds that can form selectively and add as a template for copying, which is necessary for retaining useful information. Phosphate is important because it alone has three functional sites – two to form a polymer, and one to convey solubility. Only the furanose form of the sugar seems to manage the linkage, at least under conditions likely to have been around at the time and ribose is the only sugar with significant amounts of the furanose form. I believe the absence of ribose means the absence of reproduction, which means the absence of life. But whether these necessary components are there is more difficult to answer.

Gravitational Waves, or Not??

On February 11, 2016 LIGO reported that on September 14, 2015, they had verified the existence of gravitational waves, the “ripples in spacetime” predicted by General Relativity. In 2017, LIGO/Virgo laboratories announced the detection of a gravitational wave signal from merging neutron stars, which was verified by optical telescopes, and which led to the award of the Nobel Prize to three physicists. This was science in action and while I suspect most people had no real idea what this means, the items were big news. The detectors were then shut down for an upgrade to make them more sensitive and when they started up again it was apparently predicted that dozens of events would be observed by 2020, and with automated detection, information could be immediately relayed to optical telescopes. Lots of scientific papers were expected. So, with the program having been running for three months, or essentially half the time of the prediction, what have we found?

Er, despite a number of alerts, nothing has been confirmed by optical telescopes. This has led to some questions as to whether any gravitational waves have actually been detected and led to a group at the Neils Bohr Institute at Copenhagen to review the data so far. The detectors at LIGO correspond to two “arms” at right angles to each other running four kilometers from a central building. Lasers are beamed down each arm and reflected from a mirror and the use of wave interference effects lets the laboratory measure these distances to within (according to the LIGO website) 1/10,000 the width of a proton! Gravitational waves will change these lengths on this scale. So, of course, will local vibrations, so there are two laboratories 3,002 km apart, such that if both detect the same event, it should not be local. The first sign that something might be wrong was that besides the desired signals, a lot of additional vibrations are present, which we shall call noise. That is expected, but what was suspicious was that there seemed to be inexplicable correlations in the noise signals. Two labs that far apart should not have the “same” noise.

Then came a bit of embarrassment: it turned out that the figure published in Physical Review Letters that claimed the detection (and led to Nobel prize awards) was not actually the original data, but rather the figure was prepared for “illustrative purposes”, details added “by eye”.  Another piece of “trickery” claimed by that institute is that the data are analysed by comparison with a large database of theoretically expected signals, called templates. If so, for me there is a problem. If there is a large number of such templates, then the chances of fitting any data to one of them is starting to get uncomfortably large. I recall the comment attributed to the mathematician John von Neumann: “Give me four constants and I shall map your data to an elephant. Give me five and I shall make it wave its trunk.” When they start adjusting their best fitting template to fit the data better, I have real problems.

So apparently those at the Neils Bohr Institute made a statistical analysis of data allegedly seen by the two laboratories, and found no signal was verified by both, except the first. However, even the LIGO researchers were reported to be unhappy about that one. The problem: their signal was too perfect. In this context, when the system was set up, there was a procedure to deliver artificially produced dummy signals, just to check that the procedure following signal detection at both sites was working properly. In principle, this perfect signal could have been the accidental delivery of such an artifical signal, or even the deliberate insertion by someone. Now I am not saying that did happen, but it is uncomfortable that we have only one signal, and it is in “perfect” agreement with theory.

A further problem lies in the fact that the collision of two neutron stars as required by that one discovery and as a source of the gamma ray signals detected along with the gravitational waves is apparently unlikely in an old galaxy where star formation has long since ceased. One group of researchers claim the gamma ray signal is more consistent with the merging of white dwarfs and these should not produce gravitational waves of the right strength.

Suppose by the end of the year, no further gravitational waves are observed. Now what? There are three possibilities: there are no gravitational waves; there are such waves, but the detectors cannot detect them for some reason; there are such waves, but they are much less common than models predict. Apparently there have been attempts to find gravitational waves for the last sixty years, and with every failure it has been argued that they are weaker than predicted. The question then is, when do we stop spending increasingly large amounts of money on seeking something that may not be there? One issue that must be addressed, not only in this matter but in any scientific exercise, is how to get rid of the confirmation bias, that is, when looking for something we shall call A, and a signal is received that more or less fits the target, it is only so easy to say you have found it. In this case, when a very weak signal is received amidst a lot of noise and there is a very large number of templates to fit the data to, it is only too easy to assume that what is actually just unusually reinforced noise is the signal you seek. Modern science seems to have descended into a situation where exceptional evidence is required to persuade anyone that a standard theory might be wrong, but only quite a low standard of evidence to support an existing theory.

Brexit Strikes Again

Last week, I reblogged a post that I found to be quite interesting. It appears that currently there is chaos in Britain regarding Brexit, and it is worth looking at how we got here. As Philip Henley pointed out, the vote to leave the EU in accord with the results of a referendum was passed by Parliament by 498 votes to 114 votes. That became law and is the default position should a deal not be made. The May government then set about negotiating a deal with the EU, and the EU became very hard-nosed: its attitude was that it would make the situation as tough for the UK as it could reasonably do to discourage others from leaving, but also leave an easy route to remain. One of the provisions of this deal was the so-called Irish Backstop, nominally a transition period to ensure the Irish border could be kept open, but with the proviso that it would remain in force until the EU decided that it was no longer needed. The net result of this is the possibility that it could refuse indefinitely, in which case Northern Ireland would effectively become part of Eire. This deal was rejected by Parliament three times.

As her tenure as PM came to an end, Parliament came together and the ordinary MPs rebelled and took over the House, claiming they were trying to reach an agreement. At first they came up with eight possible options, but when put to the vote, all eight were rejected. Obviously, they were a negative bunch. After a panicking weekend, they reduced the number of options, but again nothing got a positive vote. Missing from the choice was “no deal”; the reason being that the Speaker stated that was the default option. That meant that everybody who wanted the “no deal” exit voted no to everything and those who wanted various deals cancelled each other out. Of course, there was no alternative deal that was realistic; both sides have to agree for there to be a deal and the EU stated there were no alternatives. Accordingly, the “no” vote won. What we learn from that is that in such a situation, the order you do things is important.

Part of the problem appears to be there are a number of hidden agendas. Nicola Sturgeon wants another referendum, as do the “Remainers”. Sturgeon simply wants a precedent for another referendum for Scotland leaving the UK, and presumably taking the North Sea Oil revenues with it. The “Remainers” simply won’t accept they lost the Parliamentary vote. Corbyn merely wants to be Prime Minister. I have heard no clue what he really wants to do about Brexit, other than annoy the government.

How could this have been different? First, decisions should be final, and the first decision was whether to leave or not leave. An overwhelming majority took the leave option. MPs then had the obligation to make that decision work. That vote was the time to argue whether the first referendum was fair, binding, or what. They declined because they did not want to come out and tell their own constituents they don’t care what they think.

The next step is to negotiate a deal. The mathematics of decision-making is called Game Theory. In terms of mathematics, there are clear requirements to get the best from a negotiation, one of which is that if the bottom line is not met, you will walk. For that to mean anything, it has to be credible. If the UK politicians want anything better than the May deal, then “No Deal” must be on the table, and it must be credible that will apply. Johnson is as near to credible as possible. If he is undermined, the UK is highly likely to lose.

At this point, the behaviour of some MPs is unconscionable. They have no proposal of their own, they have heard Johnson say he will try for a deal, and Johnson has laid down just one condition – the Irish backstop must be replaced. He should be supported in his efforts unless they have a better idea. There is talk of Johnson being undemocratic for suspending Parliament for 23 days. As Philip Henley has pointed out in the previous post, 23 days is far from being unprecedented. Johnson has the job of negotiating some sort of deal with the EU with a pack of yapping dysfunctional MPs offering a major distraction. The fact is, none of them have come up with something workable.

Now Parliament has voted to block a “no-deal” exit. Does that mean there must be a deal? No, of course not. First, the bill must be passed by the Lords. Since they are largely “Remainers”, they probably will pass it, although when is another matter. However, for that to be effective, there actually has t be a deal on offer. The only one that is the one they have voted out three times. The EU says they will not offer another one, although what would happen if Johnson offered a workable option to the Irish border is uncertain. The Commons also voted that the UK request another extension. Whether the EU would be interested in that is less certain; they must be on the verge of saying they want rid of this ridiculous situation. Note if only one EU member votes against it, it fails. Then after demanding an election for the last few months, Corbyn has vetoed one before Brexit date, deciding instead he wants another referendum. (His problem is that many of the Labour seats come from regions that voted strongly for leaving.) Just what that would solve with this dysfunctional lot of MPs eludes me. However, the so-called blocking vote has arisen because a number of Conservative MPs have defected. They were always “Remainers”, but their defection means Johnson at best runs a minority government that will not accept anything, or everybody else votes in Corbyn as Prime Minister. That is unlikely, so it will be Johnson who goes to Brussels to ask for a deal or an extension. The question then is, how intense will his asking be?