(Permalink) It is difficult for an amateur to write scientifically about topics such as astronomy and cosmology. Indeed these are domains where things move very fast, and what seems «scientific» or «reasonable» today may seem ridiculous in three years. For this reason, please consider the publishing date of this chapter (January 2016) for any judgement or analysis.
Moreover, cosmology is greedy of ad-hoc entities, such as the Big Bang, inflation or dark matter, or it goes far beyond the experimental range, with things like symmetry breaking (chapter IV-9) or black holes. In such conditions, the boundary between science and pseudoscience is not always clear, and it sometimes moves unexpectedly, leaving the good faith thinker stranded on the wrong side.
This explains why this chapter was published well after the others of this part on physics. I first wrote a detailed but «risky» version, but now I prefer to prepare a more synthetic version, topic per topic.
Finally, among the many open problems in astrophysics and cosmology, I simply treat those for whom I have original ideas, or for which the theory of logical self-generation sheds some light.
The chapter VIII-2 is specifically dedicated to the formation of the stars and planets.
I claim anteriority for all the ideas of this chapter, for January 2016, or for the indicated addition dates. Also check on the Wayback machine.
(Permalink) As part of the Big Bang theory, physicists are already struggling to explain the tremendous inflation of the universe, from microscopic dimensions to its today cosmic immensity. But the instant of origin is an even more thorny problem: To move from a single point to the universe of the first moments, however small it was, we need an infinite expansion rate.
This problem hides another even bigger: how space and time themselves could «appear»? The very idea that they can «appear» is extremely strange.
Physicists are getting along with evoking a time of Plank for the zero instant, and for the zero point a Plank size, both incredibly small, but not null, below which there is no defined dimensions. So as large the inflation was, it was still at a finite rate. And understandable.
The logical self-generation theory explained in this book allows for a more accurate description. Indeed, according to this theory, space and time do not exist in themselves. They do not «contain» the elements of the universe, but they are the structure, in the meaning of the Sets Theory, of the set of all these elements. Structure that we perceive as «space» and «time» (chapter III-5). So that there is no difficulty that they appear, expand, or have curvature and other relativistic geometries.
We saw in chapter III-4 that the first content of the universe would have been a simple loop of logical implications «demonstrating themselves each other». This is a single element, not defining any structure, hence not any space or time. Then a first logical implication gives a second element to the series. With two elements, this already defines a straight line, with a measurement scale. In addition, this line is instantly defined over its entire length, to infinity on both sides. Then, with further iterations in the series, other elements appear. Three define a plane, four define a volume, etc. which therefore appear as the way these elements position themselves relative to each other. After, the number of dimensions, the size and geometry of this set depends on its contents (relativistic particles), but this solves the big problem of the appearance of space. We also saw in chapter IV-3 that time is none other than the unfolding of the series, that we perceive as the time passing. So that it really starts with the series, and it is not defined before.
As to the passage of a zero size to a finite size, this problem simply does not arise any more: at the stage of the single element, there are no dimensions, nor null neither finite. But as soon as two elements exist, there is a finite dimension.
(Added August 18, 2020) In more this geometry can be any, spherical for the classical Big Bang, or Euclidean for a flat universe. So the Universe can be flat and infinite from the very first logical iteration, without needing an infinite growth rate at the instant zero.
(Added August 18, 2020) Yet this still leaves a difficulty: in this case, the Big Bang necessarily filled only a finite part of an Euclidean universe, and so there should be a border, beyond which there is only empty space, even still today. Yet there is another clean solution to this problem: if one of the starting elements does not define his place relative to the others, then its effect is the same everywhere. So it can fill instantly and entirely an infinite Euclidean universe, and it will do so in a totally homogeneous way. This nicely matches a recent hypothesis by physicists, of a constant scalar «field», equal everywhere and filling the whole nascent universe with matter particles, with a very constant density. It is finally interesting to see our «metaphysical» cogitations to connect so well with the most advanced modern physics.
(Permalink) The emergence of the concept of the Big Bang, immediately following the one of Relativity, led to the idea that space and time themselves were created at the moment of the Big Bang. Thus the Big Bang was not an explosion occurring at a given point of an existing empty Euclidean space, but the inflation of the universe itself.
For such a model to be coherent, it was needed that the universe has another geometry than Euclidean: since the 1930s, it is considered that our universe would be a hypersphere, that is the equivalent of the surface of a sphere, but in three dimensions instead of two (De Sitter space). Thus no place is privileged, and the inflation of the universe is reduced to an increase of the radius of the hypersphere.
This theory had a testable consequence: just as we can go around the Earth while moving in a straight line, the light could go around our universe and back from the other side, and even go several times around. So I remember that in the 1980s astronomers tried to find multiple images of the same quasar, looking in opposite directions. They found nothing of this kind, but today we know that quasars shine only a relatively short time, making this experiment more difficult than expected.
However in the 2000s the precise measurements by NASA of the curvature of the universe shown that it is very low, less than 10%. Thus the visible universe is nearby Euclidean!
To save the hypersphere, it then needs to have an incomprehensibly larger radius than the dimensions of the visible space, which are already fantastic.
So, we need to consider again that the Big Bang may have occurred in a point of an Euclidean universe. Yes, but then how this infinite universe was created? At this point the logical self-generation theory is useful. We saw in the previous subchapter how it predicts the appearance of space and time. According to this process, there is no problem for any geometry to appear, which can be a totally Euclidean universe, as well as the classical hypersphere. Also this Euclidean universe is instantly defined up to infinity, even very far from any content.
It nevertheless remains that an explosion in a Euclidean universe must be much larger than the visible universe, to produce a uniform density. The notion of an Euclidean space does not solve the problem of the incommensurable size of the universe.
But the explosion at a point of an Euclidean universe would bring back the antic concept of the universe having an edge. People who would live there would see one side of the Universe filled with galaxies, like on Earth. But on the other side, there would be only emptiness and absolute darkness. Not even the primordial background radiation at 3°K!
(Permalink) Inflation would be a fantastic increase in the volume of the universe, which happened immediately after the Big Bang, between a sub-microscopic state and the huge dimensions it has today. It is understood as the thermodynamic expansion of the universe as a result of its temperature and pressure, just as a gas in a piston. The explosion of the Big Bang, in short. The various changes in physics would be the cause of such a release of energy, the most recent being the primordial nucleosynthesis (helium formation) within three minutes after the Big Bang. But other more powerful transitions occurred before, the most famous being the Great (dis)Unification (appearance of the four known forces of physics, from a single force). Today inflation is well characterized by data from different satellites.
This does however not explain why the universe is so uniform today: this requiers that the different parts of the Universe were communicating with each other at some time, while moving away from each other at superluminal speeds. This is called the horizon problem. This is why physicists assume an additional inflation, of unknown cause, which so much expanded the universe than we would see only a tiny bit, homogenized by this monstrous expansion. The cause of this cosmological inflation remains subject of debate among several hypotheses, and is even not accepted by all. Personally I keep other assumptions open:
-The homogenising could have occurred earlier, at a time when the universe was relatively stable and its parts would have had time to communicate. For example, before the Great (dis)Unification, the universe would have remained a while in a metastable state, with little or no inflation. Perhaps even it pulsed, or other oddities. Then the Great (dis)Unification would have started in a random point. The (dis)Unifying flame would then had spread to the whole, in a fairly orderly manner, producing a new uniform thermodynamic inflation. Be said in passing, I find fascinating the idea of a fire burning the whole universe.
Added June 16, 2016: But there is even more extraordinary: for any witnesses who may have lived in our universe when it was still in the grand unified state, then the flame front of the (dis)unification, not only burns everything as our fire, but also the pressure of the shock wave would be such that it would distort space-time itself! As in a black hole, except that it dilates things instead of compressing them. Thus, great unified scientists, observing the flame front advancing toward them, would see the objects burning, but also these objects would expand monstrously, while their light would shift toward the red. Then they would disappear beyond the event horizon, this same horizon which still today tickles our molecular scientists (our form of life of today!!) because they do not yet understand how the universe can be uniform, if its different parts could not communicate with each other, separated by this horizon. This appalling vision of an explosion front dilating a quiet space gradually as it advances could be an answer.
-More original, the appearance of a new physics at the occasion of an event such as the Great (dis)Unification would have somehow redefined the dimensions of the universe. This would be the same process as seen above for the original singularity, but applied to new particles. It would occur without displacement of the constituents of the universe. But it may produce a fantastic increase of pressure.
That the Great (dis)Unification has started at a single point, would also explains why there is only one physics, and we do not see in our universe domains with different physics.
(Permalink) Until recently, astronomers believed that the expansion of the universe was slowing, from the gravitational pull of the different parts the ones on the others. However in 1998 precise measurements have shown a surprising phenomenon: since about five billion years, the expansion is accelerating again. Today no one yet knows why, and we see blooming expressions such as «dark energy», which are good at least at making understand... our ignorance.
I would very timidly venture into hypothesis.
When I wrote the first version of this chapter (unpublished) I supposed that the accumulation of high-energy cosmic rays would eventually build up a greater pressure than the force of gravity. However I since realized that it does not: indeed, if the universe doubles in size, the pressure is divided by approximately twelve (Mariotte law says eight, but the adiabatic law applies in this case) while gravity is divided by four... so that the pressure due to cosmic rays may prevent the universe from collapsing beyond a certain radius, but not accelerate its expansion. In more the production of cosmic rays is considerably reduced today, in comparison to what it was 5-10 billions years ago.
I also supposed that the «flat» areas (not bent by gravitation) between the galaxies would eventually put pressure on the curved areas, by some relativistic effect. This is in pure speculation, but some scientists developed a similar idea: dark matter and dark energy would be the same thing, but attractive in the presence of matter and repulsive in the intergalactic voids.
Added in December 20, 2016: In the previous sub-chapter, we envisioned the Dantesque view offered to scientists living into the grand-unified physics, seeing the appearance of our own physics. What we see today looks just like this, the appearance in progress of a new physics, still unknown and incomprehensible for us. Just that this new physics would operate at a much slower time scale than ours...
(Permalink) (Sub-chapter added January 31, 2019)
I would like to make a remark here: the curves showing the expansion are hardly distinguishable from non-accelerated expansion: both curves are within the measurement errors. I link to one curve of the University of Alberta site, (carefully selected, because other curves on the same page are in a logarithmic scale, which may induce non-math savvy people in thinking that there is a strong acceleration). In this image, stars in the blue zone show accelerating expansion, while stars in the red zone show decelerating expansion. Constant expansion is at the limit between the two zones. The measures show a slight preference for the blue side, but they straddle both sides.
So, it may happen that further more accurate measures show that there is no accelerated expansion after all, just that the expansion would now be proceeding at a constant speed. How this would be possible? To understand how, let us remind that the expansion rate is determined by two forces:
1) the expansion caused by the big Bang, and still happening today. It is equivalent to a positive (outward) pressure which increases the size of the Universe.
2) Gravitation, which makes a negative (inward) pressure, trying to collapse the Universe.
Until about 5 billions years ago, the second force was strong enough to slow down the expansion. However this slowing nearby stopped being effective today. I think there is a simple reason: in the meanwhile, galaxies gathered in clusters linked by gravitation, making the mean distances much longer, and thus weakening the gravitational inward pressure. In thermodynamic terms, the number of particles in the galaxies «gas» decreased, which always result in a decrease of the (negative) pressure. At a pinch, the gathering in clusters may have raised the «temperature» of the galaxy «gas», thus producing the small observed acceleration.
So that, instead of an acceleration, what we are seeing now is simply the large clusters being decoupled, no longer linked by gravitation. If so, the universe will continue to expand eternally, but at a constant rate. The clusters will continue to collapse in giant galaxies, separated by forever increasing expanses of empty space.
I like this simple explanation. Normally I should do a science paper with that, with the galaxies thermodynamics calculus and all. But there are not enough information available on the internet for this.
As I never heard anything of this kind mentioned before, I claim precedence for this idea on January 31, 2019. It occurred to me only some days before.
(Added on May 5, 2020)
(Permalink) The picture facing cosmologists today is becoming more complex. Indeed, we no longer have one, but several mysteries:
- The accelerated expansion... real or systematic error? See the article in Quanta Magazine.
- Two different groups of results for the Hubble constant
- Curvature of the Universe much smaller than expected, if any.
Among the different hypotheses, one is evoked: our universe would not be homogeneous, and its curvature would not be the same in all directions. Thus, the Hubble constant would not be the same according to the portion of the sky where such or such team would make their measurements. I would add that if we have a positive curvature in one direction and a negative curvature in another direction, that could also explain why the NASA found a zero average curvature.
Finding a non-homogenous universe would be an extremely interesting result, giving a glimpse of phenomena which may have happened during Inflation or even before.
(Permalink) Gradually, as astronomers discovered the architecture and properties of galaxies, they understood that much of their mass escapes any direct observation, and can only be detected by its gravitational effects. And not a little: up to eighty percent of the total mass of the universe! This invisible mass, called dark matter, is very unevenly distributed: rare or absent of small objects (globular clusters), it is detected in the halo of the galaxies, and especially the massive halo of galaxy clusters. Understanding also emerged that it played an important role in the formation of the first galaxies, too fast to happen with the visible matter alone.
So dark matter responds only to gravitation. It does not emit neither absorb any radiation, which makes it actually invisible (but not literally «black»).
Today this dark matter is sufficiently well known for eliminating trivial theories (light effects, distance...) and ad-hoc theories (modified gravitation, etc. which cannot hold in front of the precise maps of the repartition of dark matter into galaxy clusters). Astronomers also eliminated theories such as the MACHO (Massive Compact Halo Object, like black holes, mini stars, solitary planets... not found in sufficient quantity). So this leaves only the theories of the WIMP kind (Weakly Interacting Massive Particles), that is particles with a mass, but which do not interact with ordinary matter. But here the choice is still widely open: neutrinos or hypothetical variants (sterile neutrinos, axions), supersymmetric partners of known particles, and even new and unknown fields. We even not know the temperature of this dark matter, that says it all!
Can the logical self-generation theory predict hypothetical particles of dark matter? Not really, as long as it does not enter in the detailed description of the causes of the different fields. But if it does, then it is no longer distinguishable from classical physics. The only original thing I find to say is something like this:
In the early stages of the Big Bang would have existed unified particles interacting by a single force (probably gravitation). During the Great (dis)Unification, these particles have been transmuted into our existing today particles: quarks, photons, electrons, which would start to interact according to the four forces existing today (gravitational, electric, weak, strong). However, since this transmutation released a fantastic amount of heat, it would have produced a gigantic inflation of the universe.
(Reviewed and corrected in xxx 2017, see previous version on wayback machine, January 30, 2017)
Scientists generally admit that particles of dark matter are «ashes» of this fantastic conflagration. Such ashes would be incapable of interacting, as they would be at a minimum energy level (in addition of being sensitive only to gravitation). However, the few observations beginning to emerge today speak of excess gamma rays or positrons, in areas rich in dark matter, the most tempting being a line at 130Gev. Other experiments try to detect the rare impacts of particles of dark matter, with still doubtful results.
This enormous energy leads to another hypothesis (of which I claim the precedence from the January 30, 2017, see the wayback machine): the particles of dark matter would not be «ashes», but remaining «fuel», that is grand-unified particles which survived the Great (des)unification, because they had not enough time to react at this moment. Thus these original particles (the single-force particles of the Big Bang) would still be there today, but almost undetectable.
This model holds if it is assumed that the primordial particles need to encounter a quark or an electron to transform itself, by receiving information from it (according to the process seen in Chapter IV-9, where a particle needs to receive information from a domain to convert). They could still do so today, but the opportunities are extremely rare, due to the very low density of the current universe. Moreover, the reaction products would be indistinguishable from our ordinary matter. Only the release of energy would signal the reaction. This same energy which consumed the universe during the Great Unification.
(Added on January 25, 2016, revised and corrected in August 2017) This has an unexpected consequence: the (very theoretical) possibility of a «dark matter engine», where it is converted into energy by contact with ordinary matter. In doing so, it would release much more energy than antimatter! The energy of the inflation of the universe! Well, in practice, dark matter is far too dispersed, and only extreme gravitation can manipulate it. So no cars running on dark matter, not even spaceships. But it could be concentrated enough in an accretion disk near a black hole. This would explain the fantastic energy generated by some supernovas, gamma-ray bursts and quasars. If the conversion of dark matter actually releases 4860 times more energy than the fusion of hydrogen, it is understandable that even a small proportion is enough to explain the incredible violence of these objects.
(Added in August 23, 2018:) Why we do not find dark matter?
Scientists are increasingly annoyed: none of the experiments designed to detect dark matter has been able to find any. According to the theory explained above, there can be two reasons:
(Added in August 23, 2018:) It would be transmuted well before arriving on Earth.
Indeed, that dark matter does not show electromagnetic interaction does not mean that it has no interaction at all. It could even interact easily, transmuting itself by simple contact. Of course, in the immensities of the galactic halos or galaxy clusters, these interactions are rare, and dark matter is stable there. But in a galaxy like ours, we have dust clouds dense enough to block the light. They could also be enough to absorb dark matter too, explaining that it is not found in the disk of galaxies. Would it venture into our solar system, that it would meet the solar wind. In conclusion, the best place to detect these interactions would be the outer edge of dust disks, or in galaxies rich in dark matter.
(Added in August 23, 2018:) Its disintegrations would already be observed, but wrongly attributed.
The idea here is that the transmutation would take place on contact, just before an ordinary interaction. The latter would then appear as the impact by an ordinary cosmic ray! However a large-unified particle can not transmute at random: the result must have a zero electric charge, a zero colour charge, and be symmetric matter-antimatter (since the current asymmetry appeared after the grand-unified particles).
If the transmutation produces a pair of particles, then one of them is necessarily anti-matter. Furthermore, only one of the two may actually react, while the other escapes free. This would produce a detectable flow of antimatter. Precisely, while looking for data, I found that positrons were detected in cosmic rays, peaking at an energy of 275 Gev. Scientists indeed attribute these positrons to the disintegration of dark matter particles. There also are anti-protons, the only stable baryon which can result from this process.
If the transmutation produces a single particle, it cannot be a baryon, or any particle with an electric charge or colour. This leaves little choice: photons, Z bosons, or neutrinos (the latter appearing more and more like their own anti-particle). In the case of the neutrino, the impact would appear as the action of a high-energy neutrino, whether it interacts or it continues on its way. In the case of the photon, we would have the appearance of the absorption of a gamma ray (this would be the cosmic background, but it should then have a measurable energy peak, or even privileged directions). In the case of a Z, it would cause a transmutation of a quark within the impacted particle. In any case, only in-situ observation, in space, would allow to differentiate a transmutation from the impact of an ordinary cosmic ray.
(Added November 2019) An Arxiv paper tells a probable emission at 3.5keV, from a sterile neutrino decay. If so, the transmutation of dark matter would not yield such a huge ammount of energy. But this would also produce apparent non-detection, if the particle transmutates in ordinary matter before showing its true nature.
(Added in June 18, 2020, anteriority claimed for this date, see the Wayback Machine). I also realize one thing: since dark matter particles are orbiting the galaxy, they have stellar velocities, in the 250km/s range. This is very little for a particle: with such a low energy, they even cannot penetrate a detector!! Let alone reach ground-based devices. Thus these particles would exist only in the galactic halo, transmuting long before reaching the Earth. We still have a chance of catching them with a detector in space, for example behind the Moon. For detection, we can expect various effects: detection of phonons, dents on ultra-polished surfaces, double V traces in aerogels, perhaps traces in a bubble chamber if we find a liquid remaining stable in space. Since the particle would transmute into a normal particle and an anti-particle, a magnetic field would bend the two traces in opposite directions, while a gamma detector would indicate the decay of the anti-particle.
(Permalink) (Revised and corrected in August 2017)
This is possible. Indeed, our galactic neighbourhood contains a notable proportion of it. Moreover, we can reason with a particle of dark matter in terms of orbits and trajectories, as for a vulgar meteorite. That is, the individual trajectory of a dark matter particle can be deflected by a star. This is how dark matter spreads and forms its specific structures in the galaxies.
We can therefore assume the following scenario:
- Usually, in our galaxy, the particles of dark matter have a speed of the order of 250km/s, just as the stars. This does not normally allow capture by a solar system.
-However, all the possible orbits can be occupied, so that we can imagine a particle of dark matter in a galactic orbit very close to the one of the Sun.
-The relative speed then becomes very low, which allows a capture by interaction with a planet. This is how long-period comets are captured by Jupiter, and brought into short-lived orbits near the sun. A halo of dark matter can thus form around the sun.
However, the gravitational map of the solar system is well known, and nothing of this kind has been detected: the amount of dark matter in orbit around the sun is therefore very low. (Added August 23, 2018: this was well studied about the Pioneer anomaly, which suggested an unknown mass in the solar system. But finally nothing such was found)
Of course, dark matter can be attracted inside the sun. Does it accumulate there? In any case, even if it interacts little, it will be significantly slowed down by its gravitational influence, and it will eventually arrive in the dense heart, where the probability of reaction is stronger. Thus a star might have dark matter inside, but it would survive only for some time. But we can consider that dark matter can play a significant role in the functioning of very dense stars, exactly as neutrinos do.
(Added August 23, 2018:) The analyses added to the previous subchapter explain that there would be no dark matter in our solar system, or that any dark matter that would venture there would be quickly transmuted, well before arriving in the heart of the Sun
(Permalink) The equations of Relativity say that the heart of a black hole is a point. This does not satisfy scientists, because in a point all measurable dimensions become infinite. But this is not what causes me the more concern: if we accept that the object at the center has some size, so its surface is in the past, relative to its center. Which is probably pretty unhealthy. Of course we can imagine several solutions, or even that the problem would not arise in this way:
-The Heisenberg uncertainty would allow the mass to exist in a certain volume, or more precisely for some time.
-Even so, the situation is uncomfortable, because of the enormous pressure. Presumably, the object at the center does in the reverse way all the steps of the Big Bang, Big (re)Unification, etc. This implies that there are several types, according to their degree of regression. The logical self-generation theory also states that these transitions are not required to always give the same result: each black hole would be different.
-If the reversion is sufficient to allow for a point-like object, then we have a singularity. But nothing says that the gravitational field is defined at an infinitely close distance of this point. Physicists speak of the Plank distance, bellow which size is no more defined. Thus gravitation would be nowhere infinite, even with a true singularity.
Recently Hawking theorized that black holes would disintegrate slowly, emitting a black body radiation, quite simply. This arises a problem: Let us consider a black hole formed from a number of protons and neutrons. Suppose it loses mass. But the number of protons and neutrons (called baryonic number) is forced to remain constant: it is a conservation law, strong and inviolable. So, assuming we can get there, what is left when the protons lost 99.99999% of their mass? And that the black hole disbands, by lack of mass? In any case there is no evidence of such objects of very low mass, but with an immense baryonic number. No super-light protons either.
Added February 14, 2016: The recent first observation of a black hole merger event showed that about 5% of its mass was lost to gravitational waves. This is different of the Hawking process, but still it shows that a black hole can lose mass. But it does not tell at which point it can lose mass.
Added January 30, 2019: The above problem would not happen, because when the thermal radiation of the black hole is hot enough, it can radiate particles by the Hawking process, and thus lower its baryonic number. Yet, since it lost energy in collisions, it still does not contains enough energy to materialise all the particles its baryonic number allows. So most probably the Hawking process would work less and less in the final stage of the evaporation of a black hole, and finally stall. The emissivity of the black hole would come to zero, cancelling the Hawking process before total evaporation.
Added January 30, 2019, from a Quora question: A supplementary problem is that a black hole colder than the cosmological backgrouns (2.3°K) receives more energy than it would emit. The evaporation would simply not exist, for stellar sized black holes. And there is no known mechanisms forming smaller black holes.
Added January 30, 2019: Pity, because a black hole in this state could then be used as a «reactor» Star Wars style: its mass would remain about constant, and we just need to drop matter in when we need it produces energy.
Black holes are an excellent example of a topic which was until recently considered as pseudoscientific by the establishment. Scientists however theorized their existence (although reluctantly) since the 1930. And especially, everybody could see since 1918 the powerful jet emanating from the heart of the galaxy M87 (found by American astronomer Heber Curtis of the Lick Observatory, and precisely this galaxy is nicknamed «Virgo jet», although its galactic nature was recognized only in 1956). When I was a kid, I was dumbfounded by this thousands light years jet: there had to be something monstrously large and powerful, much larger than any possible star, to produce such a huge tongue of fire. But my demands for explanation received this only reply: the core of the galaxies contain «only» a dense cluster of stars (which by magic never bump in each other). And the jet was «a mystery». And in more I was a kid, so that I «could not understand»! It was in 1961, and, in France, country of the enlightenment, the public schools were still forbidding children to look at the eclipse...
This kind of things is probably why we have so many pseudoscientific theories today: their authors shoot at random, in hope to catch some theory which would be recognized later. Unfortunately for them, science's heart has only one love: truth. So that its recognition can be earned only with hard work and cleverness, and the long row of rejected pretenders have to come back home, their penis half mast...
(Permalink) This is a long sought after mystery. Scientists agree to say that comets would be residues of the formation of the solar system, of the outer rim of the accretion disk precisely. However there is a hitch: comets are not in orbit, but on free fall trajectories. Some has so few orbital energy that they even straightforwardly hit the Sun (actually most known comets have elliptical orbits. But this results of their capture by heavy planets like Jupiter. Comets which never interacted with any planet have free fall orbits. Let us call these ones virgin comets, by opposition with captured comets)
So scientists posit the existence of a huge reservoir of comets at a great distance of the Sun, which would rotate so slowly that some are only appearing today. I am sceptical, since, in 4.5 billions years, the farthest would still had hundreds of occasions to approach the sun, while only one encounter can capture or destroy them.
Anyway this does not explain why they are in free fall. This requires that they are not formed in orbit, but at a fixed place relative to the sun. and since their free fall time is very short compared to the life of the Solar System, this implies that this happened recently, perhaps still today.
I see one explanation: comets would form at the bow shock, the place where the solar wind encounters the galactic wind. Today we are in a relatively low density and hot gas region of the Galaxy, but some millions years ago the Sun passed through galactic arms, possibly through dense cold dust clouds. If so, the bow shock was much denser, closer and colder, so that matter was able to accrete in comets, using the electrically charged cold dust process that we shall see in chapter VIII-2.
At a pinch, the carbonaceous materials which are so common in meteorites, and are thought to be comet residues, may not be original matter from the Solar System, but matter captured later, when passing through a dense cloud in a galactic arm.
A last mystery may also have a much simple solution. Several recent comets, like Kohoutek or Ison, displayed an unusually high luminosity while they were still far from the Sun, leading astronomers to announce then as the «comet of the century», promising spectacular displays. But later, they were barely visible with the naked eye. So why such virgin comets would exhibit much more luminosity than the captured comets, while they are still in the outer parts of the solar system? There is a sinple reply: true virgin comets would have frost, which sublimates easily, making them more luminous while they are still far. But when they come closer to the Sun, this frost is gone, and so they are like any captured comet, outgasing mostly water vapour from inside. Such frost was observed by the Rosetta probe: it forms at night, and dissipates in a minute at sunrise.
Which matches well the above model, where these comets formed recently, approaching the Sun for the first time.
Added on April 26, 2020:
(Permalink) (antecedence on Wayback Machine) a plausible scenario on the origin of 'oumuamua has just been proposed by three scientists from the Astrophysics Laboratory of the University of Bordeaux: Sean Raymond, Yun Zhang and Doug Lin (article in futura science). Let us remind that 'oumuamua, the first interstellar asteroid detected, had several very curious characteristics: a very elongated cigar shape, no comet tail, but still a reaction to sunlight indicating a much lower density than rock. The hypotheses were going well, for example that it would be a «space dust bunny», or even an extraterrestrial spaceship. At least nothing known in our solar system. We shall probably never know what it was, because it is now moving very fast away from our probes. It would indeed need a very fast craft, but with enough fuel to brake on arrival.
However, this team has come up with a scenario: 'oumuamua would have been ejected from its original system, after passing too close to its sun, a red dwarf. Why a red dwarf? Because a red dwarf is denser and cooler than our Sun, allowing an asteroid to penetrate its Roche limit without being vaporized as with our Sun. However, there is still enough heat to melt rocky bodies (or in the case of a comet, to keep only the rocky fraction). Then 'oumuamua would thus have melted. But inside the Roche Limit, it would also have been spaghettified, deformed into a cigar by gravitational forces! So here is a plausible origin for the shape and trajectory of this body.
However this does not really explain the low density (nor how low it can go). Our authors assume a body formed of pebbles, but then I think it would have disintegrated.
This is where I can make a proposition: although the molten 'oumuamua lost almost all its gas, there would be still enough left to make bubbles, and give a bubbly slag. Molten rock has a noticeable surface tension, which the glass-blowers make use of. In its natural state, lava can form veils or threads. And slag, therefore. Already the first pictures of the Spirit rover on Mars showed lava slag with holes much larger than what we can see on Earth. And in the vacuum in near weightlessness, these bubbles can grow almost without limit.
How low can the density of 'oumuamua go? On Earth some pumice can float, which makes a density of less than 30% of that of the raw rock. So in the vacuum, where nothing constrains the swelling of the bubbles, the density could go much lower. 10%, or even less.
Another clue, the passage near a red dwarf only lasts some minutes, which is very insufficient to melt an entire body of one hundred metres. But a body of a few metres can melt entirely, and give a homogeneous liquid which can make beautiful bubbles.
Thus 'oumuamua would be an expanded rock, which explains well its low density, with the scenario proposed by the scientists of Bordeaux. Even its color fits: it is the color lava takes in the presence of oxygen.
Ah, if we had had the Vishvakunta project (chapter VIII-10), we could have tested 'oumuamua in a few dozen minutes, including measuring its mass and composition. But the funny thing is that if this object had touched Earth, it might have disintegrated in the air without reaching the ground.
(Permalink) Added in February 2017:
The recent study of Mars by landers like Opportunity and Curiosity brought contradictory results: there are very sure proofs of large water flows, yet there is not enough CO2 in the air to sustain a warm enough climate for liquid water. This lack of CO2 is inferred from lack of carbonate rocks. Orbital photographies also show a large number of puzzling land shapes which have mostly no equivalent on Earth: huge chaos, cataclysmic water flows, oversized water springs (dried up since), etc.
I give here a model explaining all these, of which I claim precedence for February 2017.
First we observe on Mars several «dust mountains», which would be remnants of former polar caps. On Mars the polar caps are cold traps attracting the few water in the air. In more, winds deposit here a mixture of dust, sulfate dust, and ice dust, which exact proportions may depend on epoch. Pressure then cement the ice, or the sulfate, making of it a solid material. Such things are visible for instance in Lucus Planum, part of a whole belt south west of Olympus Mons, and in many craters, like mount Sharp in Gale crater. Opportunity landed on such a deposit, mostly made of iron sulphate. These things today appear dry and dusty, because water ice sublimates quickly. But under this thin dry surface, the bulk composition can still be a mixture of dust and of firm water ice.
Although it is less obvious, places like Margaritifer Terra could also be such deposits. This place, and many others, shows large polygonal cracks and chaos, looking as if a rigid surface layer had broken and was transported above a muddy underground layer. This can be explained in the following way: when frozen mud layers are thick enough, geothermal heat can melt the bottom. Or simply the layer is salty, explaining that it remains soft in the Martian cold! What happens then depends on the composition, thickness, slope, etc.
In a first scenario, the fluid remains muddy, but moves as a landslide, resulting in:
-Upstream, cracks and chaos in the superficial layer, when mud is flowing under, or whole valleys like Valles Marineris and its dependencies.
-Glacier-like mud flows in valley bottom, braided mud flows
-Downstream, alluvial fans, mud plains, etc.
-Lobed crater ejecta would also result of an impact into mud, or into powdery sediments (dried mud).
One of the best example showing all these features is Dao Vallis, which most likely developed in a double layer of mud separated with a basalt flow.
A second scenario happens if the mixture allows for the separation of the silt part and of the liquid water. Large cavities of liquid water may then develop. But they are unstable, due to the Archimedes force, and thus they can erupt suddenly when they find a way to the surface. This may happen suddenly, as the surface layer is hard, and when a crack starts, it freezes at once, making it waterproof. Mars continental mud plains shows a large quantity of holes being the spring of large flow patterns, especially around Cerberus Fossae. But when the flow stops, the remaining water freezes, and then sublimates, leaving an «unexplainable» empty hole at the origin of the flow pattern.
The behaviour of Mars frozen mud may be very similar of what is found in the Yamal peninsula. However the conditions being different, the landforms in Yamal, like the famous Bovanenkovo crater, are different. We can also look in Iceland on what happens when volcanoes erupt under glaciers.
In this way most parts of Mars surface may have been reshaped several times by successive mud flows. The largest ones may be the consequence of slow geological subsidence or bulging of the surface, from transformations deep within Mars. This is how was formed Tharsis dome, the Hellas basin and the North plains basin. But today the trends seem to have changed, resulting in the recent and active Cerberus Fossae fault line, which is also the source of numerous very recent flows, and may is probably still active.
Eruptions of liquid mud result in an etched surface style unique to Mars, which can be seen in many recent flows: a layer of pure ice would form on the surface of the moving flow, while cracking from its movement, like oceanic ice pack on Earth. Mut partly fills the cracks. When the flow settles, it freezes in mass. But then the pure ice sublimates entirely, while the mud remains in place, sheltered from sublimation, and frozen. This results in large ice pack-like patterns, in negative, showing the ice cracks as ridges, as can be seen in many places in Athabasca Vallis and Marte Vallis. A spectacular case can be seen at 4° 2'60"N, 149°39'60"E.
This explains a lot of the bizarre Mars features, but not the largest water flows. This is where we come to my original contribution. On, Mars volcanic eruptions are rare, but they may be very voluminous, and thus short, emitting large amounts of steam and CO2 in some hours. Such watery volcanic surges are known on Earth, where they can result in rain. This steam could then form a temporary atmosphere, with its own greenhouse, probably appearing as a large snow-white cloud spreading around the volcano or along the slopes. It may even totally shroud the planet. So there is a moment where liquid water can exist under the steam. However such a temporary atmosphere is not stable, and it will quickly convert in liquid water, in a matter of hours. These events would then result in episodes of dilluvium-sized rainfalls, covering a whole region, able of gouging the numerous large water channels on Mars. Indeed these channels look like formed by catastrophic surges, to the contrary of our Earth valleys formed by small but constant water streams. Such torrential surges are known on Earth too, and they are not water, but mud, able of transporting blocks of hard rock, and much more efficient than water at eroding the terrain. An excellent example of this is Maadim Vallis. Precisely the Spirit rover landed on the alluvial fan of Maadim Vallis, which partly filled the Gussev crater. This terrain appeared as a mixture of dirt and basaltic stones, typical of the torrential surges which happen in heavy rainfalls. As an evidence, this terrain shows a meniscus at the contact of older landforms, matching the behaviour of thick mud. Curiosity landed on the same type of terrain, but it quickly found sandstone deposits corresponding to gentler events. Nevertheless, most probably none of these events lasted more than some hours, at best some days, until the water froze and whatever remained exposed sublimated.
Some types of lava also break into dust when they contain water, like in the Pinatubo eruption. These eruptions can form mud, or soft deposits, including on the cones themselves. This would explain a lot of volcanic features on Mars too, like in Arsia Mons. Even Ulysses Patera and Tharsis Tholus shows lobed ejecta, as if the whole volcanoes were made of mud, or at least powdery pyroclastic deposits.
But by far the largest flows on Mars emerged from the large canyon system Mariner Vallis, which joins west side the faults systems around the Tharsis dome, and extend north-east side as far as Lani chaos. It seems that what happened is that faults opened in the hard bedrock, under a several kilometres thick layer of frozen mud, probably uplifted there by the bulging of the Tharsis dome. Then geothermal heat emerged along the faults, directly or from underground lava flows. This resulted in widespread melting of the lower mud layers. Depending on local conditions, the upper layers remained in place, or caved in to form the canyons, or even they were dragged, to form the chaos. In any case these events resulted in colossal surges of water toward the north basin.
Added June 16, 2016:
(Permalink) I do not know if Greenpeace would love the idea of a nuclear life :-). I saw this idea mentioned in a scientific review (I do not remember by who, sorry): if our molecular life is based on the interactions between molecules, nuclear life would be based on the interactions between nuclear particles. It is unclear whether such a thing is possible, but in any case this hypothesis leads with a mathematical rigour to consequences much further the most hair raising speculation of the wildest science fiction.
First, the necessary physical conditions are fantastic pressure and temperature, such as our ordinary atomic nuclei are broken, or extraordinary nuclei become stable, leading to a new state of matter, fully nuclear. These conditions are realized on many levels, in a neutron star. Near the surface at the transition between atomic and nuclear matter, and deeper, near the centre, where hyperons might exist (nuclear particles containing unusual heavy quarks, such as the strange quark, stabilized by the pressure). Thus a neutron star could have several «ecospheres» nested within each other.
One of the most extraordinary consequences of this assumption is that, for living beings formed from nuclear matter, their subjective time would be billions of times faster than ours: the time of a wink on Earth, thousands of generations would have succeeded in one neutron star inhabited with such beings. Moreover, for them, their world would appear to them as our spherical Earth, but thousands of times larger: a world with 100,000 continents and as many billion people, civilizations, races, religions, etc. If such things exist, then there could be infinitely many more people in neutron stars than in planets.
Such beings may however not be able to travel in space: their bodies would disintegrate in a flash of radioactivity. Could they communicate with Earth? If they try, their signals are to be found in the gamma spectrum. But it might be difficult for them to even think that molecular beings like us can exist. Anyway their time scale communication would make things difficult: the light already takes several generations to just go around their world. No internet, therefore, not even Marco Polo: their continents would be as isolated and separated as the stars are in our molecular world.
What the article did not say is that our universe itself may have allowed this, during some microseconds after the Big Bang, when it was still filled with a soup of nuclear particles. Earlier in its history, the quark-gluon plasma could also allow it (its complexity is worth the one of the primordial soup of the Stanley Miller experiment). Even earlier, before the great (dis)unification, other conditions may have existed at different times. Of course, the further we go back, the more it is speculative, but the idea above of scientists observing the great (dis)unification is not entirely impossible.
this first version was based on a false assertion regularly published
in the media, as what
the (linear) velocity of stars around a
galaxy would be independent of the radius of their orbit.
Which, with the help of a few simple calculations, would lead to a
density law in 1/R2 for
all the galaxies. I therefore drew conclusions from this
law, on the structure and evolution of galaxies. However, more
professional publications indicate a totally different exponential
law. This law in 1/R2 is thus false, as well as most of
the conclusions and mechanisms that I derived of it. This kind of
mistake is not the first time: this is what happens regularly when we
try to make science on the basis of «simplified»
information published in the media, including «scientific»
However, I refuse to bear the responsibility for this error, because it is not my fault, and it came from expectedly reliable sources.
What remains is less original, but there are still some elements of which I claim the precedence, see the wayback machine of xxx.
(Permalink) Several versions of the law of distribution of the density of an elliptical galaxy have been published. The content of the wikipedia page on this subject has been modified several times. Astronomers seem to only recently converge on a model called PoLLS (Power Law Logarithmic Slope). In any case, the only Google result is a paper published by Cornell University, signed Cardone, Piedipalumbo, Tortora, on which I base my reasoning. Equation 10 on page 3 tells that the density decreases exponentially with the radius, to a reason which is itself a power of the radius. The density of a galaxy therefore decreases exponentially, with a different reason depending on whether we are near the centre or at the periphery.
we follow a radius toward infinity, the mass increases only by a
finite quantity. Older models had the mass increasing at infinity
along the radius, which required a truncation at a certain distance,
in order to keep a physical sense (and to be able to calculate
integrals, such as the mass as a function of the radius). (My
model in 1/R2 also had this problem, requiring a
truncation, so I am «comforted» from thinking that
professional astronomers also had to face this difficulty.)
This PoLLS model does not lead either to an infinite density in the centre, which eliminates other difficulties.
However, there is a free parameter γ, which defines different density profiles for the same mean radius. After this parameter, a galaxy of a given average radius can be more or less fuzzy.
In a galaxy, stars are so numerous that they can be treated as a «gas», just like our ordinary gases which are formed of molecules. Their large number allows to define thermodynamic quantities which are statistical averages, homologous to the familiar pressure, density, and temperature.
My contribution was then (and I still claim precedence January 30, 2017, as I never saw it published) that the distribution of matter in a galaxy results from a thermodynamic equilibrium between the pressure of the stars gas and its own gravitational field. It is this equilibrium which would lead to the exponential distribution PoLLs seen above. We can even assume that the parameter γ above would reflect the effect of the «temperature» of the star «gas». Indeed, it is easy to imagine that, with equal mass and equal number of stars, a galaxy with more agitated stars will spread more.
This reasoning would also apply to globular clusters. However, the latter often have different distributions, for two reasons:
-They would oscillate, alternating compressed and dilated states
-The encounters between stars produce fusions, or separations of binary systems, which complicate things. Thermodynamically, these encounters would be equivalent to «chemical reactions», changing the statistical properties of the «gas» of stars, and thus the distribution at equilibrium.
My only regret in the suppressed version was that I was not able to demonstrate my distribution law, starting from the state equation of the star «gas» (which is also valid for dark matter). But professional astronomers did not succeeded either: the paper above proposes a «fit», that is to say an equation which best fits the observations, not a demonstration as in classical thermodynamics. Maybe the problem is more complicated with stars than with molecules.
(Permalink) My false model in 1/R2 had a seducing feature: the density increased to infinity in the centre, which naturally explained the formation of a black hole at this place. Moreover, this black hole had a size representing a constant proportion of the galaxy, since if it exceeds a certain mass, then the thermodynamic equilibrium seen above would prevent more stars from approaching it. Precisely astronomers seem to have noticed such a law.
However the PoLLs law indicates that the centre has a rather flat profile, which does not automatically give a black hole, let alone a constant proportion. We are therefore obliged to admit that this black hole appears by hierarchical mergers between stars, and that the law of proportion is only a statistic. Looking for more information on this law (August 2017), I finally found that it had been established only on 75 galaxies... and that we already know a dozen exceptions. It is therefore a statistical average, rather than a determinism.
Just that, the bigger the galaxy is, the faster these encounters happen: big galaxies always have a black hole, but globular clusters rarely, if any. Indeed, for an encounter to occur, a massive object must brake, with disrupting the fields of stars it crosses. The larger the object, the more efficient the braking, leading to chain mergers, accelerating exponentially. And the faster as the galaxy is big. It is, however, difficult to fix the exact limit at which a central black hole appears, as it is a random process. Thus some globular clusters could have one, while a central black hole has not yet been found in the larger Magellanic Cloud, yet much larger. What is probably happening is that in these places there is a concentration of massive objects, which not yet had time to assemble into a single one.
That there are large black holes of «abnormal» mass suggests a totally different origin in this case: gatherings of dark matter, which would have occurred before the formation of galaxies and stars. But there are other more classical explanations: during a galaxy coalescence, certain geometries would be much more conducive to the fall of large quantities of matter in a single centre. Imagine, for example, two identical galaxies, rotating in the opposite direction, and meeting flat like cymbals. In theory all the gas has its rotation cancelled, and it falls quickly in the centre, leading to an extra-large black hole. Real situations could be almost as effective: coalescing galaxies often leave elliptical galaxies empty of gas, indicating that it has been entirely absorbed, probably during a merger event, forming a large black hole.
One wonders why the central black hole does not swallow its whole galaxy. The reason is simple: for an orbiting star to approach, it must dissipate its kinetic energy. A process which could take thousands of billions of years for a galaxy like ours.
(Added October 7, 2020)
A recent explanation has been proposed by scientists (source lost, sorry): during the formation of a black hole, or during coalescence, they would receive a rather strong impulse, ejecting them at high speed. Once this is done, they end up in the galactic confines, or even in intergalactic space, where their chances of collision are extremely low.
(this has been proposed as an explanation for dark matter, but attempts to search for them did not found then in sufficient quantity).
My contribution is that, when a galaxy has more than some mass, its gravitational attraction becomes strong enough to cancel their speed. Wandering black holes would then fall straight back towards the core, where their chances of collision are significant. They would also be slowed down there by interacting with many stars in the dense areas of the Galaxy. They could therefore gather in the centre, forming a super-massive black hole.
This process is well visible in galaxy collision simulations: when the two nucleus merge, they settle very quickly in one. That is, each individual star of a given nucleus is very efficiently braked when going through the other nucleus.
This well explains why these super-massive black holes only appear in galaxies of sufficient size.
(Permalink) Spiral galaxies function differently from ellipticals. We saw that in an elliptic, the density as a function of the radius results from a thermodynamic statistic. This statistic takes place between very particular objects, stars, which do not meet (or seldom) and do not interact with each other (no electric fields or other). They interact only by their gravitational field. Dark matter has the same properties, which explains why it cannot be differentiated from the stars, other than of course by its lack of luminosity. The two act together to give a single PoLLS type distribution, even if the proportion of dark matter is higher in the halo.
In a spiral, exactly the same processes are taking place. However, there is an an additional phenomenon: fresh intergalactic matter falls on the galaxy. This matter is so diluted that the atoms do not meet, and it simply follows the gravitational field, behaving like dark matter. It was even hypothesized that dark matter would be that, but this explanation was not retained.
However, as it approaches the centre of the galaxy, this matter compresses. Then, at a moment, the density becomes sufficient to allow for its atoms to meet, which leads to a different thermodynamic statistic, the one of the gases (the ordinary gases as we know them). And this statistic leads the gases to collect in a very different geometry from the PoLLS distribution: an accretion disk. This is the origin of the disk of the spiral galaxies.
This disc is enriched with all the fresh gas which falls on it. But after a certain density, the matter it contains turns into stars, according to the well-known process. (Strictly speaking this process also forms dust, but the latter also ends up gathering into the stars).
These stars, once formed, no longer interact with the gas of the disk. They thus escape the thermodynamics of gases, to join again the one of the stars and of dark matter, which gather in the PoLLS distribution.
Thus, the gases act as a pump, which attracts mass at the level of the disk, disrupting the PoLLS distribution. This may result in a bump, an excess over the ideal PoLLS curve (density versus radius), at this place, in the spiral absorbing intergalactic matter (prediction made on August 15, 2017). So I would not be surprised if the observed density curves finally show such a bump. It would be all the more pronounced as the rate of absorption is high. Unfortunately, the rare curves published in magazines accessible to the public show everything: a flat, a simple change of slope, or even a hollow. In the defence of these reviews, it will be pointed out that these curves are difficult to establish, and that this has been attempted only in a small number of galaxies. In addition, it is often the speed curve which is published. A bump on the density curve then translates into a steeper part on the speed curve. And this is what some published curves seem to show. It will be known when these curves will be established with sufficient precision (and that magazines intended for the general public will publish this exact result. A text in incomprehensible jargon which costs $30 to read is NOT a publication. A text which does not contain more information than the title is NO MORE a publication).
What my previous theory predicted, is that thermodynamic equilibrium would always bring the density curve of a galaxy to an equilibrium. This reasoning is of course also valid for a PoLLS law. This leads to a result which is well verified: the need to keep the thermodynamic equilibrium (to keep the PoLLS curve) makes that the supply of fresh matter at the level of the disk pushes the older matter either towards the nucleus or toward the halo. From there come the well separated bulb and halo of the spiral galaxies, both formed of ancient stars. (precedence claimed for the www, see wayback machine on January 30, 2017). It is only when the supply of fresh matter ceases that the thermodynamic equilibrium clears the bump and fuses these two structures into one, to form a normal elliptical galaxy, at equilibrium.
In practice, we indeed observe all the intermediate states: a wide disc, a narrow disc, a simple dust band, and no disc at all.
(Permalink) It can never interact according to the thermodynamics of gases. It therefore never forms an accretion disk. This prevents it from braking itself when approaching a galaxy. This would be why the particles of dark matter remain in the periphery, in the halo of the galaxies, or even in the immense halos of the clusters. On the other hand, they always do so according to the PoLLS distribution.
If a spiral galaxy contained dark matter at the origin, then it would have been pushed towards the centre, or towards the halo. However, dark matter is not observed in the centre of galaxies, which gives an indication of their formation: dark matter, supposed to have accelerated the formation of galaxies, would in fact only have prepared the ground, forming the halos of galaxies. Only the ordinary matter could have braked and approached closer to the centre, thanks to its different thermodynamic properties. Hence the impossibility of dark galaxies (which we do not actually observe, even if we finds some abnormally rich galaxies) (precedence requested for August 17, 2017).
(Permalink) We therefore have a simple model, based on known facts and safe assumptions, which predicts all the traits, size ratios and and behaviours of galaxies, and even a lot of details. The only unproven hypothesis is that dark matter is really matter, and not a field or a relativistic effect. But since it behaves like matter, we do not take much risk.
At this point, we can deduce the equation of state of dark matter. This was even done, and I was told by a scientist of the «Science Center» in Second Life, and it actually matches the one of particles interacting only by gravitation. Strictly speaking, I could have done it myself, but I had not enough reliable data.
Finally, I allow myself here with a little curious prediction (January 3, 2016): some galaxies contain large clouds of dark dust. An example is M104, well known as the Sombrero Galaxy, surrounded by a vast belt of opaque dust, where apparently stars do not form. Why should they not form, in an environment which has all the features to form them? The catch is that, if stars form here, then they are mainly formed of dust, so that they can not start nuclear reactions (or very little). We would then have a new class of objects, the brown giants, rocky object like the Earth, but as massive as stars. Probably their surface remains incandescent, and other amazing properties. They would likely have a thick atmosphere, which would give them the appearance of red dwarfs, but much smaller at equal mass (and therefore much more difficult to detect). I do not know if such stars really exist, and if so, shall we find them some day?
(Added in August 17, 2017) considering the enormous pressures inside such objects, they would probably be reduced to the size of a white dwarf. And, like a white dwarf, they would emit a very blue light. The spectrum would not necessarily be different, since they could have an atmosphere, for example hydrogen. But their mass-to-radius ratio would be different. Their average mass would probably be inferior to the usual masses of stars, by their formation from a very dusty matter.
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