P1: The Cosmic Smog model for solar system formation,
and the nature of 'Dark Matter'
[The Four Pillars of GAU, Part 1]
Ben Franklin Centre for Theoretical Research
PO Box 27, Subiaco, WA 6008, Australia.
A fundamentally new model of how solar systems form (and evolve)
This article describes what is believed to be a fundamentally new model of how solar systems are formed, and how their components evolve with time. Among the possibly novel concepts put forward are the following:
1. Independent formation, no protoplanetary disc. In the model, all the components of a solar system form independently. How the system looks after a given time depends on the extents to which gravitational interactions have proceeded.
2. Incipient solar systems ordered over time. In the model, an incipient or newly-forming solar system contains an essentially random distribution of solid bodies. These may be ordered under the influence of gravitational forces, over sufficiently long times, into a planar distribution of planets and asteroids around the equatorial axis of a central star.
3. The nature of 'Dark Matter'. Incidentally to the main model, it appears that the 'Dark Matter' sought for many years by astrophysicists and cosmologists is merely undetected ordinary matter beyond solar systems.
The story so far
Knowledge of our Solar System (the suite of planets and other celestial objects, including comets) extends right back into remote human history -- 30,000-year-old cave paintings in France are claimed to include such knowledge.
By the 1930s, the picture had been well established that the known planets orbited about the Sun in a disc-like plane, which roughly coincided with the plane of the Sun's equator. Pluto, at that time treated as the ninth planet, was discovered in 1930.
Figure CSM1. Our Solar System. From .
Back then, no other solar systems were known to science, it was not even known whether other such systems existed. With no other examples to compare with, it was more or less assumed that if there were other solar systems, they would probably be similar to ours, seen as quite well-regulated and ordered.
Even the distances of the planets out from the Sun fairly closely followed a pattern described by Bode's Law . This was an empirical law, a rule-of-thumb, without any established theoretical basis.
The plane in which the Sun's planets orbited was not a perfectly flat one, nor did it exactly match the equatorial plane of the Sun. The following table gives some relevant data.
Figure CSM2. Inclinations of planetary orbits. From .
The table shows the names of the planets, followed by the angles between their planes of rotation and the ecliptic (the plane of rotation of Earth). Then there are the angles between the planetary planes and the the Sun's equatorial plane. The last column shows the angles between the planetary planes and the invariable plane (the weighted average of all planetary orbital and rotational planes).
It can be seen that the various planes differ by up to 7 degrees or so, not huge, but still significant. We'll see later what these differences imply.
Back in the 1930s, our knowledge of the Solar System was pretty well limited to the nine planets (then including Pluto), the asteroids (smaller bodies, mostly found in the Asteroid Belt between Mars and Jupiter), some comets, and a number of known moons of the planets. Mercury and Venus have no moons, the Earth has one, Mars two, and Jupiter, Saturn, Uranus, and Neptune were known to have a few each. That was the full extent of our knowledge.
Better telescopes, and rocket-powered space vehicles, have changed all that.
Our Solar System -- where we are today?
With increasing improvements in telescopes and in experimental techniques, we have come to know more about our own solar system, reaching out well beyond the orbits of Neptune and Pluto. Space probes sent to the Moon and out to the other planets yielded huge amounts of new, often surprising, information. More and more moons were found circling the outer planets, and more and more became known about the regions beyond Neptune.
Figure CSM3. Tilting of planetary orbits. From .
The graphic shows the orbits of the planets, out to Neptune, lying in an approximate plane. Beyond Neptune, the orbits of dwarf planets such as Pluto and Eris are strongly tilted. The dwarf planets mostly lie in what's called the Kuiper Belt, a region beyond Neptune only investigated in recent decades.
The Kuiper Belt is usually represented as another disc containing relatively small planetary bodies, of the size of Pluto or less, orbiting the Sun beyond Neptune. Neptune orbits at 30 AU (Astronomical Units, the distance of Earth from the Sun), and the Kuiper Belt lies at 30-100 AU from the Sun [9, 11].
The Kuiper Belt  is known to contain over 1000 identified objects, including at least three dwarf planets (Pluto, Haumea, and Makemake), More than 100,000 KBOs over 100 km in diameter are believed to exist. Originally considered a planet, Pluto's status as part of the Kuiper Belt caused it to be reclassified as a "dwarf planet" in 2006.
In more recent times, the outermost part of the Kuiper Belt, from 50 AU to 100 AU from the Sun, is often treated as a distinct entity, the Scattered Disc. Within the Scattered Disc lies the dwarf planet Eris, believed to be larger in diameter, and probably mass, than Pluto . This makes it the ninth-largest Sun-orbiting body in the Solar System.
The trend in objects orbiting the Sun will be apparent. The orbits of the eight planets lie approximately on a plane (up to 7 degrees variation). In the inner Kuiper belt, deviations from this plane are much larger -- Pluto's orbit has an inclination of over 17 degrees to the ecliptic , and is also highly elliptical (non-circular). The dwarf planet Makemake has an orbit inclined at 29 degrees.
Fig. CSM4. Orbit of Pluto -- ecliptic view. This "side view" of Pluto's orbit (in red)
shows its large inclination to Earth's ecliptic orbital plane. From .
It's of interest that Pluto's orbit can take it closer to the Sun than Neptune. This was the case in the 20-year stretch from 1979 to 1999. However, because Pluto's orbit is both tilted and strongly elliptical, the two bodies cannot ever collide, their orbits are always some distant apart.
When it comes to Eris, in the outer Outer Kuiper Belt or Scattered Disc, its orbit's inclination is higher still, 44 degrees (see Fig. CSM3). So, the further out from the Sun, the more inclined the orbits.
According to , "Eris (minor-planet designation 136199 Eris) is the most massive known dwarf planet in the Solar System and the ninth-most-massive body known to directly orbit the Sun. It is estimated to be 2,326 km in diameter,and 27% more massive than Pluto, or about 0.27% of the Earth's mass.
Eris was discovered in January 2005 by a Palomar Observatory-based team led by Mike Brown, and its identity was verified later that year. It is a trans-Neptunian object (TNO) and a member of a high-eccentricity population known as the scattered disc. It has one known moon, Dysnomia. As of 2014, its distance from the Sun is 96.4 AU, roughly three times that of Pluto. With the exception of some comets, Eris and Dysnomia are currently the most distant known natural objects in the Solar System."
Beyond the Kuiper Belt
The region beyond the Kuiper Belt is called the Oort Cloud. In contrast to the Kuiper Belt, the Oort Cloud has no pretense of being based on a disc. Instead, it is spherical, like the very thick skin of a pomelo. It is also enormously more extensive than the regions looked at so far -- while the Kuiper Belt extends out to 100 AU, the Oort Cloud goes out to 100,000 AU .
This distance is almost 2 light-years, which is about half the distance to the nearest star. In a sense, the Oort Cloud is only a theoretical concept, a way to refer to distant bodies in space which are still within the Sun's gravitational influence. But the Sun's gravitational pull at these distances is weak indeed, and if this pull is the principal force acting on a body, its 'orbit' about the Sun may be highly elliptical and take thousands of years to complete one cycle.
Figure CSM5. The Kuiper Belt and the Oort Cloud in the outer Solar System. From .
The Oort Cloud has most relevance to us as being the place where most comets appear to 'originate', that is, these 'long-period' comets may swoop in to the inner Solar System and be recorded there, before retreating back to where they came from. Because their times to complete one orbit are so long, maybe many thousands of years, we don't have any historical records of earlier appearances.
According to , "Objects in the Oort cloud are largely composed of ices, such as water, ammonia, and methane. Astronomers argue that the matter composing the Oort cloud formed closer to the Sun and was scattered far out into space by the gravitational effects of the giant planets early in the Solar System's evolution."
One reason why the Oort Cloud is treated as a sphere, rather than a disc, is because comets can appear from any direction, such as at 90 degrees to the plane of the ecliptic. Again, the further out from the Sun, the more inclined the orbits may be.
Here is how Nick Stroebel describes the situation .
"The Oort Cloud is a large spherical cloud with a radius from 50,000 to 100,000 AU surrounding the Sun, filled with billions to trillions of comets. It has not been directly observed. Its existence has been inferred from observations of long period comets. Long period comets have very elliptical orbits and come into the inner solar system from all different random angles (not just along ecliptic). Kepler's third law says that they have orbital periods of hundreds of thousands to millions of years.
However, their orbits are so elliptical that they spend only 2 to 4 years in the inner part of the solar system where the planets are, and most of their time at 50,000 to 100,000 AU. With such long orbital periods their presence in the inner solar system is, for all practical purposes, a one-time event. Yet we discover several long period comets every year. This implies the existence of a large reservoir of comets".
We do have historical records of some short-period comets, such as Halley's Comet. This is the best-known of the short-period comets, and is visible from Earth every 75 to 76 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth. Halley, like many comets, follows a retrograde orbit, that is, it orbits the Sun in the opposite direction to the planets.
Figure CSM6. The Oort Cloud, warehouse for billions of long-period comets. From .
We can record the orbit of a long-period comet quite accurately, and so could calculate when it should next appear. But even then, because comets are typically of low mass, they are easily affected by the gravity of other Solar-System bodies, which could well throw out their orbits.
Bigger bodies within the Oort Cloud
Existing telescopes and techniques can only detect Oort-Cloud objects having orbits or paths which bring them fairly close to the inner solar system.
There was much excitement in 2003 when Sedna, a dwarf planet with an unusual orbit, was detected at 90 AU, three times as far from the Sun as Neptune. Sedna never comes much closer to us -- it has a highly elliptical orbit, taking about 11,400 years per cycle, from a maximum of 937 AU to a minimum of 76 AU .
Figure CSM7. The orbit of Sedna, an Oort Cloud object. From .
Spectroscopy has revealed that Sedna's surface composition is similar to that of some other trans-Neptunian objects, being largely a mixture of water, methane and nitrogen ices with tholins. Its surface is one of the reddest in the Solar System. Sedna's exceptionally long and elongated orbit, taking approximately 11,400 years to complete, and distant point of closest approach to the Sun, at 76 AU, have led to much speculation about its origin.
Mike Browne, one of the discoverers of Sedna, realized that Sedna was something new for astronomical theory. He wrote "Seven years ago, I knew with certainty that the discovery of Sedna in a strange orbit that never brought it close to any planet was telling us something profound about our solar system. I also knew that Sedna would never divulge her secrets alone. To learn more, we'd have to find more things like Sedna.".
Sedna was the first dwarf planet detected which can be classed as a member of the Oort cloud. It has been estimated that another 40 to 120 Sedna-sized objects exist within this region . As of end 2013, four currently known objects (90377 Sedna, 2000 CR105, 2006 SQ372, and 2008 KV42) are considered members of the inner Oort cloud .
The most-recently discovered of these, 2008 KV42, nicknamed Drac (short for Dracula), is a trans-Neptunian object orbiting the Sun in retrograde motion (backwards) and almost perpendicular to the ecliptic: it has a 104-degree inclination .
In  it also says "The orbits of trans-Neptunian objects provide important clues as to how the outer Solar System took form and evolved. Discoveries of new classes of objects have led to fresh insights into the early history of the Solar System, challenging accepted theories. The discovery of 2008 KV42, the first-ever object in this region to be detected with a retrograde orbit, promises to do just that."
Dr JJ Kavelaars of the National Research Council of Canada has noted  that "Although we've been specifically looking for highly-tilted trans-Neptunians for some time now, we didn't expect to find a retrograde one. A number of theories on the formation of the outer Solar System have suggested that such things might be out there, but observational searches for them are very difficult."
What's the makeup of the Oort Cloud?
There is an important thought to be drawn from the orbit of Sedna (Fig. CSM7). Firstly, this dwarf planet never comes very close to the Inner Solar System (where the planets dwell). Secondly, its orbit is highly elliptical.
The thing is, Sedna would never have been detected with current techniques, unless it was on an elliptical orbit which happens to have brought it comparatively close to us in recent years. So, only Oort-Cloud objects with very elliptical orbits are detectable for us.
What about other Oort-Cloud objects with more circular orbits? They are likely to be undetectable at present. So there could well be a huge reservoir of such objects which we do not know about.
Moreover, further out in the hypothetical Oort Cloud, near the gravity watershed between our Sun's gravitational influence and that of the next star, the forces of gravity acting there are very weak. Objects sitting there are probably not in anything we would describe as an orbit, but are just free-floating.
Let's try for another conclusion, from a plot of comet orbit inclinations.
Figure CSM8. Inclinations of long-period comets. From .
The plot shows Inclination (tilt of the comet's orbit compared to the plane on which the planets lie) plotted against semi-major axis (distance from the Sun to the furthest point on the comet's orbit).
From the plot it is obvious that comets which orbit closer to the Sun (up to about 10 AU) have low inclinations, mostly under 30 degrees. Beyond about 100 AU (the end of the Kuiper Belt and the start of the Oort Cloud), inclinations are essentially random -- comets come from any given direction.
On this plot, an inclination over 90 degrees means one tilted beyond the vertical. This is another way of saying that the comet is retrograde, orbiting in the opposite direction to the planets. So an orbit inclination of, say, 105 degrees is the same as an inclination of 75 degrees, except that the comet runs along its orbit in the reverse direction (called retrograde).
The conclusion is that Oort Cloud has no particular structure, but is approximately the same everywhere.
There is another general inference to be drawn from the comet plan. That is, the gravitational influence of our Sun has not had any significant effect, over the last 4 billion years or so, beyond about 100 AU. Beyond that limit, the Cosmic Smog is either unchanged since its initial state, or has parts which have evolved independently of our Solar system.
Let's start to list some basic features of the Cosmic Smog model.
Initial structure of the Galaxy
Solar systems, stars, and galaxies evolve and age under the influence of gravitational forces. Our own Solar System is, from quite good evidence, believed to be about 4.6 billion (4600 million) years old. This is assumed to be the time that has elapsed since it started to settle out from an initial cloud of gas and dust.
We can present this concept as our first Proposition.
This proposition is unlikely to evoke much argument, it is the starting point for most ideas on how a galaxy or a solar system develop.
Implicit in this proposition is the assumption that a given volume of the smog in one place will have a similar mass to the same volume of smog elsewhere in the cloud. However, the "lumpiness" of the two volumes may differ.
The next Proposition, while seeming reasonable, is possibly a new element in solar system formation models.
What this Proposition means is that in a given volume of smog, as time passes, its contained mass may undergo an aggregation, or increase in lumpiness. That is, larger-mass bodies may form by the combination of many smaller bodies.
We'll come later to an explanation of how gravity acts to bring about this clumping or aggregation.
What's the total mass of the Oort Cloud?
Estimates have been made in the past of the total mass of Oort Cloud bodies. Here are a couple of estimates.
"If Halley's Comet's mass is typical for comets, then the Oort Cloud could have a total mass between 4 and 80 Earth masses" .
"Past estimates of the total mass of this Oort Cloud have ranged from about 40 times that of Earth to greater than that of Jupiter" (about 317 Earth masses) .
These estimates are largely based on the masses of comets and dwarf planets which have been detected because, during parts of their orbits, they have reached the Inner Solar System, or at least the Kuiper Belt. All these bodies have had highly elliptical orbits, if they hadn't they would never have come within range.
So such estimates do not take account of whatever bodies exist within the Cloud which do not have elliptical orbits, and so do not come into range. Taking these bodies into account might hugely increase the estimated total mass of the Cloud.
In fact, if Propositions CSMP1 and CSMP2 above are valid, it follows that the mass contained within the Oort Cloud could be many orders of magnitude greater than that of the whole Solar System.
The logic of this is quite clear. If our Solar System was formed by aggregation of Cosmic Smog matter within a sphere of radius 100 AU, itself within a much larger Oort Cloud sphere of radius 100,000 AU, the volume of the larger sphere would be one billion (one thousand cubed) times that of the smaller. If the original Cosmic Smog was reasonably uniform, the Oort Cloud could have had anything up to a billion times the mass of the Solar System.
However, in P4, the fourth article in the quartet, we will see how the mass of the Solar System may have been enhanced by billions of years of scavenging in its passage through the Oort Cloud. This would have greatly raised its average density compared to the average for the Oort Cloud.
From this perhaps surprising result, it appears that the nature of the so-called "Dark Matter" long sought by astrophysicists and cosmologists may at last have been revealed. It is merely undetected ordinary matter beyond solar systems.
It will be recalled that the 'Oort Cloud' concept is only a convenient way of referring to the volume outside the Solar System and the Kuiper Belt, up to where the influence of nearby stars takes over. It is not a sphere as such. Nevertheless, this does not affect the above reasoning.
Current theories of how the Solar System formed
Back in the 1950s, one popular theory on how our Solar System formed was that a passing star drew out a long filament of matter from the Sun. As it departed, this matter condensed into the planets, leaving them orbiting the Sun.
At the time, it was not known whether other solar systems existed. If the passing star theory was accepted, it meant that solar systems might be very rare occurrences, depending on special movements of stars.
However, the most commonly-favoured theory at present is that the planets and other Solar-System bodies outside the Sun formed from a "protoplanetary disc" of gases and dust lying around the Sun. Here is part of the writeup from Wikipedia .
"The formation of the Solar System is estimated to have begun 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the centre, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed".
"This widely accepted model, known as the nebular hypothesis, was first developed in the 18th century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace. Its subsequent development has interwoven a variety of scientific disciplines including astronomy, physics, geology, and planetary science. Since the dawn of the space age in the 1950s and the discovery of extrasolar planets in the 1990s, the model has been both challenged and refined to account for new observations".
"The Solar System has evolved considerably since its initial formation. Many moons have formed from circling discs of gas and dust around their parent planets, while other moons are thought to have formed independently and later been captured by their planets. The positions of the planets often shifted, and planets have switched places".
Figure CSM9. Artist's conception of a protoplanetary disk. From .
At first sight, the Protoplanetary Disc theory might not seem very different to the Cosmic Smog model presented here. But, it has some notable defects, and fundamental differences.
The first defect is, no grounds have ever been put forward, why matter surrounding the Sun should form into a disc. Why should a mass of random gas and dust particles start orbiting the Sun, all in a plane? This is not in accord with standard physics.
Second, if there really was some mechanism why a protoplanetary disc could be formed, why are the Inner Planets not on a precise plane, rather than varying by some 7 degrees from each other and from the Sun's equatorial plane? (see the table in Figure CSM2 above).
Thirdly, if all Solar-System bodies except the Sun formed from a protoplanetary disc, why are their orbits more inclined, the further they are from the Sun?
Fourthly, if the known Kuiper-Belt and Oort-Cloud bodies originated from the Sun's family, how did they get thrown out into the far recesses? Researchers in this area have themselves pointed out the lack of a likely mechanism.
Fifthly, if a disc was formed from gas and dust around the Sun, why should it form in the plane of the Sun's equator? There is no physical reason for this, as a random event the disc might be expected to have a random inclination to the Sun's equator.
There are more difficulties to be explained when it comes to the moons of the planets, and to instances where planets themselves spin at highly-inclined angles to the ecliptic. Let's go on to look at this.
Moons in the Solar System
Back in 1950, the planets were known to possess 28 moons or natural satellites, including our own Moon. Since then, space probes and improved telescopes have allowed the number known to hugely increase. At end 2013, the total was 173. Detailed data on these moons is given in .
As well as those circling the planets, many more moons have been found orbiting asteroids and the dwarf planets which lie beyond Neptune. As of October 2009, 190 asteroid moons and 63 trans-Neptunian moons had been discovered .
The Wikipedia summary above suggests that "Many moons have formed from circling discs of gas and dust around their parent planets", that is, these planets are assumed to have their own tiny equivalents to the protoplanetary disc. Such an assumption is liable to the same defects noted above for the Sun's postulated protoplanetary disc.
Of the planet moons, 18 or 19 are quite large, some comparable in size to the planet Mercury. These moons are large enough to have formed into spherical shapes; smaller moons are usually irregular, like potatoes.
Figure CSM10. Moons of the Solar System. From .
Let's look at each of the planets and their moons, starting nearest to the Sun. Mercury, the innermost planet, and Venus, the next one out, have no moons.
After Venus is us, the Earth. Immediately we find a problem with the protoplanetary disc concept. Our Moon is quite massive compared to the mass of the planet around which it orbits. Theorists agree that it could not have formed from a disc of material orbiting the Earth, the physics of the situation rule this out. This is especially true in the earlier days, when the Moon is accepted as orbiting much closer to the Earth than now.
And so, the Earth-Moon system is, according to the accepted lore, an exception to the disc-material matter aggregation theory. Instead, some claim that the Moon originated from a collision of a Mars-sized body with the early Earth, when some of the debris from this collision circled the Earth and then aggregated into the current Moon.
There is actually very little evidence to support this exception to the theory, but it cannot be completely ruled out, either.
Next out from the Sun is Mars, a smaller planet. Mars possesses two tiny moons, orbiting very close in to the planet -- one circles Mars more quickly than the planet rotates, so it rises in the west rather than the east.
These tiny moons are usually assumed to have been picked up by Mars from small asteroids which happened to pass close, and that is probably the case. But it is another exception to the standard theory.
There is a fascinating puzzle associated with these moons of Mars. Due to their small size, they were not detected telescopically till 1877. Somehow, though, these unusual objects were described (as recorded by the astronomers of Laputa) in Jonathan Swift's 1726 book "Gulliver's Travels", written in 1726.
The next planet out, after the four inner 'rocky planets', is Jupiter, a 'gas giant'. Jupiter is very massive, with more mass than all the other planets put together, and so it dominates the gravitational interactions of the system.
As of end 2013, Jupiter is known to have 67 moons, including those first discovered by Galileo -- Io, Europa, Ganymede and Callisto. All are quite massive, not fitting comfortably into disc-aggregation scenario. Most of the others are quite small, and 52 of them are retrograde, circling Jupiter in the opposite direction to Jupiter's own rotation and the direction of the Galilean moons.
It's obvious that these 52 retrograde moons cannot have condensed out of a disc of matter orbiting Jupiter, and they are usually classed as 'captured' by chance from passing asteroids.
After Jupiter comes Saturn, another 'gas giant'. Saturn is known to have 62 moons, including Titan, more massive than the planet Mercury. Of these 62 moons, 29 have retrograde orbits.
Then comes Uranus. Uranus contains a lot more water ice than the planets closer in, and is classified as an 'ice planet'. Uranus has 27 moons, of which 8 are retrograde.
But the really novel feature of Uranus is that it rotates "tipped on its side", at close to a right angle with the ecliptic plane. In recent years it has been discovered that all four outer planets have rings, though only Saturn has such prominent ones.
Figure CSM11. Uranus rotates on its side. From .
In fact, the tipping is over 90 degrees, so the rotation of Uranus is also officially retrograde, in the opposite direction to the other planets. It's most unlikely that such a situation could have evolved out of the conventional protoplanetary disc.
Last of the true planets is Neptune, with 14 moons, of which 4 are retrograde. One of the 4 is Triton, Neptune's largest moon by far. The likelihood of such a moon coming from a matter cloud rotating in the opposite direction is extremely remote.
While Pluto, Eris, Haumea, Orcus and Quaoar are considered dwarf planets, they nevertheless have moons. Pluto has 5 known moons, in an unusual arrangement.
Figure CSM12. Pluto and its moons. From .
Pluto and its relatively large and close moon Charon revolve about their shared centre of gravity, as normal. In addition, there are four more small moons which orbit well outside the Pluto-Charon setup. Here's some of what Wikipedia says .
"The Pluto-Charon system is noteworthy for being one of the Solar System's few binary systems, defined as those whose barycentre (centre of gravity) lies above the primary's surface. This and the large size of Charon relative to Pluto has led some astronomers to call it a dwarf double planet.
The system is also unusual among planetary systems in that each is tidally locked to the other: Charon always presents the same face to Pluto, and Pluto always presents the same face to Charon. Because of this, the rotation period of each is equal to the time it takes the entire system to rotate around its common centre of gravity. Just as Pluto revolves on its side relative to the orbital plane, so the Pluto-Charon system does also."
It will be apparent that hardly anything that is currently known about the planets and their moons is a good fit with the protoplanetary disc theory. Let's go on now to see what the Cosmic Smog model says.
Let's use the term 'planetesimals' for all the solid bodies assumed to exist at the time of solar-system formation and up to the present. This will include asteroids, comets, dwarf planets, and planets and stars themselves.
It has been noted earlier that many of these planetesimals contain a lot of water in the form of ice. This is as might be expected, water is made of hydrogen and oxygen, the most common and third most common elements in the universe.
Uranus and Neptune were noted as 'ice planets'. All comets contain some ice -- their characteristic 'tails' are mostly made up of water molecules, evaporated from their ice stores, and pushed away from their path by the pressure of sunlight (their tails always point away from the Sun, not along their path of passage). Distant Sedna was noted as having a composition "largely a mixture of water, methane and nitrogen ices".
So the quotation likening the planetesimals to snowballs is not so far off. Bodies closer to the Sun than Jupiter, however, are typically mostly rock. We'll see later why this might be.
We've already seen that the area containing the greater Solar System, which is referred to as the Oort Cloud, very probably contains a huge mass of planetesimals. These likely consist of a wide range of aggregations, from dust up to giant planets in size.
So what marks out our Solar System from the rest of the Oort Cloud, why do we know it is different? It may be different only in that one of these aggregations happens to have achieved star mass, and in so doing has been able to start the thermonuclear process which generates the light of the Sun and most other stars.
If this aspect of the Cosmic Smog model is correct, it has a number of implications. It means that our Oort Cloud may contain many other planet-sized objects, right up to the size of Black Dwarfs.
Black Dwarfs are normally thought of as the final stage in evolution of a small star, of perhaps 70% or less the mass of the Sun. Here is some of what Wikipedia says .
"A black dwarf is a white dwarf that has sufficiently cooled that it no longer emits significant heat or light. Because the time required for a white dwarf to reach this state is calculated to be longer than the current age of the universe (13.8 billion years), no black dwarfs are expected to exist in the universe yet.
A white dwarf is what remains of a main-sequence star of low or medium mass (below approximately 9 to 10 solar masses), after it has either expelled or fused all the elements for which it has sufficient temperature to fuse. What is left is then a dense ball of electron-degenerate matter that cools slowly by thermal radiation, eventually becoming a black dwarf.
If black dwarfs were to exist, they would be extremely difficult to detect, because, by definition, they would emit very little radiation. They would, however, be detectable through their gravitational influence."
In the Cosmic Smog model, black dwarfs may also be formed by aggregation of planetesimals, up to a mass too low to invoke any thermonuclear reaction which would generate enough light for them to be detected.
There are a number of points of interest in the Wikipedia writeup quoted above. In the first paragraph, the view is expressed that no black dwarfs would be expected to exist in the universe, conventionally supposed to have an age of 13.8 billion years.
In a stablemate article, The Placid Universe Model -- Why the Universe is NOT Expanding , I give evidence that the Universe is infinite in space and time, so that the 13.8 billion-year age does not apply. In fact, bodies with above definition of black dwarf are known to exist in profusion, under the name of rogue planets, which we'll look at below.
In the second paragraph it notes "What is left is then a dense ball of electron-degenerate matter". In another stablemate article, Inside The Earth -- The Heartfire Model, I suggest that the fate of cosmic bodies, from planetesimals up to stars, depends on the mass they have accumulated in formation -- not a novel idea in itself.
In particular, for bodies of the mass of Mars and above, during the aggregation process their centres become compressed enough to form neutron-rich cores -- some stars, called neutron stars, consist almost entirely of neutrons, while in larger planetary bodies, like Jupiter, decay of these neutrons provides the internal heating observed. Neutron-rich is equivalent to 'electron-degenerate matter' here.
In the third paragraph it notes that because they do not give out light, "they would, however, be detectable through their gravitational influence." If Proposition CSMP2 above is valid, with solar systems produced by the clumping of matter already in their sphere of influence, this ability to detect with gravity would not necessarily apply. This is because any given volume of the Oort Cloud would have a similar mass to any other volume. Only the degree of clumping would differ.
In our model we are starting to look at a quite different picture of the Oort Cloud, one which contains a profusion of planetesimals of masses right up that of a star.
What would happen if, elsewhere in the Oort Cloud, one of these planetesimals built up to the mass of a star? Our Solar System would then become a binary star system, which, as we will see later, is a common occurrence in the menagerie of star systems.
Let's go on now to look at rogue planets, exoplanets, and black dwarfs.
Fifty years ago, we knew a fair amount about our own solar system, but nothing about other solar systems. Extrasolar planets (planets around other stars) were only a matter of speculation.
It was not until the 1990s that the first of these exoplanets was identified. By the end of 2013, more than 1000 had been found, with the Kepler Space Telescope throwing up more than 3000 more candidates . It is claimed that, on average, every star has at least one planet, which means our Galaxy must have trillions. The Milky Way also contains possibly trillions of rogue planets , which are not bound to any star.
In the stellar range, black dwarfs are of lower mass than the next-heaviest category, brown dwarfs (which emit only feebly in the visible or infrared wavelengths), and higher mass than a conventional planet, such as Jupiter.
We'll see later that modern telescopes have revealed a vast array of planets around other stars, distant from our Sun. None of these 'exoplanets' were seen directly, instead they have been deduced from their effects on the stars which they circle.
The techniques used rely on the planet having mass enough to produce a detectable effect on the movement or perceived light radiation of the parent star. For this reason, most of the exoplanets known have been quite massive, much above that of Jupiter. However, with improving techniques, smaller planets have been found.
Even the best of modern telescopes does not have the resolving power to image the disc of anything outside the Solar System. There is a theoretical construction, an array of band-arc telescopes in space , which should be capable of any desired resolution, but that has not been progressed beyond the concept stage.
Many of the exoplanets found qualify as black dwarfs (of mass between brown dwarfs and Jupiter-plus-size planets). The techniques used favour large planets, as these have the greatest effect on their parent star.
Some of these planets orbit extremely close to their parent stars, and are called 'Hot Jupiters' . They are of interest here, because they do not fit into the protoplanetary disc theory. In  it says "They are all thought to have migrated to their present positions because there would not have been enough material so close to the star for a planet of that mass to have formed in situ. It has been found that several hot Jupiters have retrograde orbits and this calls into question the theories about the formation of planetary systems".
About Rogue Planets
Rogue planets are planet-sized bodies which are not associated with particular stars, but instead float free in the galaxy. It was noted above that "The Milky Way also contains possibly trillions of rogue planets". .
In  it says "A rogue planet, also known as an interstellar planet, nomad planet, free-floating planet or orphan planet, is a planetary-mass object that orbits the galaxy directly. They have either been ejected from the planetary system in which they formed or were never gravitationally bound to any star or brown dwarf. Astronomers agree that either way, the definition of planet should depend on its current observable state and not its origin."
It will be apparent that the Cosmic Smog model explains the existence of rogue planets very naturally, while the protoplanetary disc theory cannot. Moreover, there may be huge numbers of such rogue planets -- estimations suggest there may be up to 100,000 free-floating planets for every star in our Milky Way . If this is the case, our Oort Cloud may hold as many as 100,000 planet-sized objects.
The incipient Sun
If the Cosmic Smog model is valid, then in the early days at the beginning of formation of the proto-solar-system, this was just an area of the Oort Cloud where some planetesimals were starting to aggregate towards the mass of a sun.
Before the development of a significant single mass, all the constituent planetesimals would have been close to free-floating. Gravitational interactions would be occurring, but movements would have been essentially random. There would be no longer-range 'orbits' formed, instead there would be masses of smaller bodies in something like Brownian Motion.
Without a central, energy-radiating star yet in operation, the planetesimals would still be in their original state, consisting mostly of ice. At first the incipient star would be a star-mass object, not yet radiating, but possibly beginning to convert its initial water ice to hydrogen and oxygen. These atoms would be held to the new star by its high gravity.
Once the incipient star had gone through the ignition phase, and had started to radiate energy, this radiation would begin to 'dry out' the ice from closer planetesimals. This is presumably why asteroids and other bodies which are now in the inner part of the Solar System consist mostly of rocky material. In losing their ice, their masses would have been reduced.
Even before ignition and the start of radiation, once a solar-mass body had formed, it would begin to influence its closer planetesimals, which would either take up orbital paths, or fall into the incipient sun, or combine with other planetesimals.
A mass of randomly-moving planetesimals, beginning to orbit the incipient sun at all angles to the sun's equatorial plane, would be starting a process of converting chaos to some sort of order. Collisions, amalgamations, splitting, and changes in orbits would reign for quite a time.
There is some support for this picture by looking at the times when different parts of the new solar system were active. We know already that the Earth is approaching 4.6 billion years old. On the other hand, the Sun is about 4.5 billion years old (p35 in  ). While results are not absolutely cut and dried, it appears that some meteorites are older than the Earth. Here is what  says about the Allende meteorite.
"Allende contains chondrules and CAIs that are estimated to be 4.567 billion years old, the oldest known matter. This material is 30 million years older than the Earth and 287 million years older than the oldest rock known on Earth, Thus, the Allende meteorite has revealed information about conditions prevailing during the early formation of our solar system."
All this fits in well with the Cosmic Smog model, with its initial aggregations of smaller planetesimals, followed by aggregation of planet-size and greater bodies. Eventually, a little later, one of these bodies gained enough mass to allow fusion of hydrogen to take place, with the production of light.
Another important event in the early history of the Solar System was the Late Heavy Bombardment. Here is how  characterizes it.
"The Late Heavy Bombardment is a hypothetical event thought to have occurred approximately 4.1 to 3.8 billion years ago. During this interval, a disproportionately large number of asteroids apparently collided with the early terrestrial planets in the inner solar system, including Mercury, Venus, Earth and Mars. The LHB happened "late" in the Solar System's accretion period when the Earth and other rocky planets formed and accreted most of their mass; it is a period still early in the history of the solar system as a whole."
Why do the Solar-System planets lie in a plane?
We've already seen that in the early days of the Solar System, the mass of planets and other planetesimals within the gravitational influence of the Sun may have followed every sort of orbit or movement possible, and may have undergone collisions or aggregations, or added their mass to that of the Sun.
To achieve the current disc-like distribution of the planets, there must have been forces which altered or amalgamated all these random orbits into the nice flat disc we see today. It appears that this was due to gravitational forces from the Sun, very slowly altering these orbits to conform with the equatorial plane of rotation of the Sun.
This idea ties in well with the Late Heavy Bombardment event of 3.8-4.1 billion years ago. If true, it means that the "straightening-out" or regularization of the orbits of the planets mostly happened around 500 million years after the Solar System first formed.
Figure CSM13. Flattening of orbits into a plane. From .
The concept also ties in well with the increasing inclinations of orbits of comets and dwarf planets -- the further they are from the Sun, the weaker its gravitational influence.
One of the modern requirements for a Sun-orbiting body to be classed as a planet is that it has cleared the area around its orbit of other significant bodies. In the same way, it might be said that for a part of space to be classed as a solar system, the central sun or suns must have cleared their section of the local Oort Cloud.
It will be remembered that our solar-system planets do not move exactly in a plane, but vary in their inclination to the Sun's equator by up to 7 degrees or so. This deviation can be ascribed to the slow pace of orbit flattening, taking up to billions of years, and its weakening with distance from the Sun. Also it is likely that Jupiter, easily the most massive of the planets, might be the most resistant. All 5 planets from Mars outward have inclinations only half a degree or so different to Jupiter's.
This concept of flattening of planetary orbits is not the current conventional view, and so few mathematical analyses of the gravitational interactions involved have been done. Let us move on now to an analogous situation which is much better researched.
The Rings of Saturn
The Rings surrounding the planet Saturn are one of the most beautiful and interesting sights in the Solar System. They are also one of the earliest discoveries, first noted by Galileo in 1610.
Figure CSM14. Saturn. From .
Here is a summary from Wikipedia .
"The rings of Saturn are the most extensive planetary ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometres to metres, that orbit about Saturn. The ring particles are made almost entirely of water ice, with a trace component of rocky material. There is still no consensus as to their mechanism of formation".
The dense main rings extend from 7,000 km to 80,000 km above Saturn's equator (Saturn's equatorial radius is 60,300 km). With an estimated local thickness of as little as 10 metres they are composed of 99.9 percent pure water ice with a smattering of impurities. The main rings are primarily composed of particles ranging in size from 1 centimetre to 10 metres."
The rings are not continuous, instead they have gaps and thin sections, which create divisions. The rings were named in order of discovery, using capital letters of the alphabet, starting with 'A'.
Figure CSM15. Divisions in the rings of Saturn. From .
The rings are therefore the flattest known objects in the Solar System. With a width up to 80,000 km and a thickness of 10 metres, they are 8 million times wider than thick.
There is a vital fact here, where the Cosmic Smog model is concerned. Saturn's Rings orbit exactly above Saturn's equator , the inclination of the ring particles' orbits to the equator is zero degrees.
The other three outer planets, Jupiter, Uranus, and Neptune, also have small ring systems, and these rotate above their planet's equators also.
A lot of mathematical analysis has gone into working out how the rings operate. They are actually quite complex, some rings having 'shepherd moons' moving within them, other rings affected by a phenomenon called 'resonance' with Saturn's major moons. But clearly the forces involved create a very stable overall situation.
Whatever the underlying mechanism, these examples prove without any doubt that orbit-flattening forces have been active to produce and maintain these amazing structures. The exceptional flatness of the ring structures, taking orbit-flattening to the max, may be due to the small masses of the component particles compared to the masses of their planets.
Beyond the Solar System
Ring-like systems have been detected around stars, apparently showing masses of small planetesimals in a flat plane around a star. An example is the star Beta Pictoris, studied with the Hubble Space Telescope .
Figure CSM16. Beta Pictoris from the Hubble Space Telescope. From .
Here is some of what  says about Beta Pictoris.
"We need to study such things because we're seeing the building blocks of planet formation and their dynamics on display. A 'congealing' planet ought to knock surrounding materials around, leaving visual clues that make the disk seem somewhat inflated.
Rochester's Alice Quillen is an expert on such interactions, which are only subject to scrutiny when the stellar disks appear edge-on as seen from Earth. The relevant stars also need to be near enough for useful Hubble imagery and young enough to be in the process of forming what can be termed embryonic planets.
Pulling all this material together for the three stars studied, Quillen and team think they're looking at the effects of Pluto-sized objects ('embryos'), about 1000 kilometers in size. But note: We haven't detected Pluto-sized objects. What we've done is to establish that such objects make sense as a plausible explanation for the action we observe in three planetary disks. Are there other explanations? Possibly so, and they may well emerge."
Formation of the Milky Way
If the Cosmic Smog model works for the Solar System, a version of it might also work for the whole of our Milky Way galaxy. This, also, might have originated as a formless Oort-Cloud type volume, and become turned into a flatter disc by gravitational forces.
But there have been no suggestions, as far as I know, that all the stars of our galaxy were once part of a 'protogalactic disc', the analogue of the 'protoplanetary disc' postulated for our solar system.
The Solar System planets have been found to rotate in directions unconnected with the plane of the Sun's equator, this being part of the evidence against them having formed from a postulated protoplanetary disc.
In the same way, the idea of a 'protogalactic disc' is negated by the fact that individual solar systems do not conform with the galactic plane -- our own Solar System's plane is inclined at an angle of 62.6 degrees from the galactic plane  (where the galactic plane is defined as the plane perpendicular to the galactic axis of rotation which has half the mass of the galaxy above the plane and half below).
If the Cosmic Smog model could be modified to describe the whole Galaxy, there should be an orbit-flattening force able to flatten the components of an initial vaguely spherical volume. In the case of our Galaxy, this gravitational force might have come from its central supermassive black hole, believed to contain a mass equal to 3.3 million suns .
Figure CSM17. Our Milky Way galaxy seen from the side. From .
There is something of a resemblance between this Milky way picture and that of Beta Pictoris. This might be a coincidence.
Wrapping up the topic -- Occam's Razor
Faced with the mass of evidence and assertions presented here, how might an intelligent person without the full array of specialist knowledge judge the validity of the Model?
There is a way. In the early 1300s, in England, a Franciscan friar and scholastic philosopher and theologian called William of Ockham developed just such a principle , now usually called Occam's Razor.
Figure CSM18. William of Ockham. From .
The essence of the principle is that, if you are presented with a number of possible explanations of a matter, you should always choose the simplest one.
I believe that the Cosmic Smog model presented here is notably simpler in its explanations than many current models, particularly where Dark Matter is concerned.
In the mystery novels of Agatha Christie, the final denouement always managed to sort out a complex situation in a credible manner. Here is Agatha's take on the situation.
* * * * * * * * * * * * * * * * * * * * *
References and Links
1. Protoplanetary Disk. http://upload.wikimedia.org/wikipedia/commons/7/71/Protoplanetary-disk.jpg .
2. Exoplanet. http://en.wikipedia.org/wiki/Exoplanet .
3. Solar System Exploration. http://solarsystem.nasa.gov/planets/ .
4. Titius-Bode law. http://en.wikipedia.org/wiki/Bode%27s_law .
5. Invariable plane. http://en.wikipedia.org/wiki/Invariable_plane .
6. Orbital Inclination. http://en.wikipedia.org/wiki/Orbital_inclination .
7. Cosmology. http://journalofcosmology.com/Cosmology8.html .
8. Outer Solar System. http://deepspaceexplorers.org/ .
9. Kuiper belt. http://en.wikipedia.org/wiki/Kuiper_belt .
10. Eris (dwarf planet). http://en.wikipedia.org/wiki/Eris_(dwarf_planet) .
11. Oort cloud. http://en.wikipedia.org/wiki/Oort_cloud .
12. Comets -- Target Earth. Video. http://www.youtube.com/watch?v=4i4pYPI8OQs .
13. Pluto. http://en.wikipedia.org/wiki/Pluto .
14. Mike Brown. There's something out there.
15. 2008 KV42. http://en.wikipedia.org/wiki/2008_KV42 .
16. The Oort Cloud. http://upload.wikimedia.org/wikipedia/commons/0/03/Kuiper_oort.jpg .
17. Orbit of Sedna. http://upload.wikimedia.org/wikipedia/commons/d/d9/Sedna-PIA05569-crop.jpg .
18. Nick Stroebel. Comet Orbits---Oort Cloud and Kuiper Belt. http://www.astronomynotes.com/solfluf/s8.htm .
19. Oort Cloud & Sol b? http://www.solstation.com/stars/oort.htm
20. Long-period comets. http://www.boulder.swri.edu/~hal/talks/oort/CIW/oort020.html
21. 90377 Sedna. http://en.wikipedia.org/wiki/90377_Sedna .
22. Formation and evolution of the Solar System. http://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System
23. The Dragon's Tales. http://thedragonstales.blogspot.com.au/2013/07/moons-of-solar-system.html .
24. List of natural satellites. http://en.wikipedia.org/wiki/List_of_natural_satellites .
25. Planets for kids. http://www.planetsforkids.org/planet-uranus.html .
26. James Kasting. How To Find A Habitable Planet. Pinceton University Press, 2012.
27. Pluto. http://en.wikipedia.org/wiki/Pluto .
28. Black dwarf http://en.wikipedia.org/wiki/Black_dwarf .
29. Rogue planet. http://en.wikipedia.org/wiki/Rogue_planet .
30. David Noel. Inside The Earth -- The Heartfire Model. http://www.aoi.com.au/bcw/Heartfire/index.htm .
31. David Noel. The Placid Universe Model -- Why the Universe is NOT Expanding, or, The real origin of CMBR, Cosmic Microwave Background Radiation. http://www.aoi.com.au/bcw/Placid/index.htm .
32. Wanted, an optical analysis for the secondary mirror of a band-arc telescopes. http://zombal.com/zomb/scientific-calculation/wanted-an-optical-analysis-for-the-secondary-mirror-of-a-band-arc-telescopes .
33. Terrestrial Planet Forming? http://www.centauri-dreams.org/?p=1495
34. Brian Dodson. What is the angle between the planes of the solar system and of the Galaxy? http://zombal.com/zomb/scientific-question/what-is-the-angle-between-the-planes-of-the-solar-system-and-of-the-galaxy .
35. Hot Jupiter. http://en.wikipedia.org/wiki/Hot_Jupiter .
36. Allende meteorite. http://en.wikipedia.org/wiki/Allende_meteorite .
37. Late Heavy Bombardment. http://en.wikipedia.org/wiki/Late_Heavy_Bombardment .
38. A Background in Asteroids, Comets and NEOs. https://lcogt.net/education/article/background-asteroids-comets-and-neos .
39. Saturn. http://www.solstation.com/stars/saturn0.jpg
40. Astro 1: `Slides' for Class 39 - The Jovian Planets and Pluto. Astro 1: `Slides' for Class 39 - The Jovian Planets and Pluto.
41. Rings of Saturn. http://en.wikipedia.org/wiki/Rings_of_Saturn .
42. What is the angle between the plane of Saturn's rings and its equatorial plane? http://zombal.com/zomb/scientific-question/what-is-the-angle-between-the-plane-of-saturns-rings-and-its-equatorial-plane .
43. The dark heart of the Milky Way. http://www.einstein-online.info/spotlights/milkyway_bh .
44. http://en.wikipedia.org/wiki/William_of_Ockham .
P0: -- The Overview article for the four COSMOLOGY PLUS articles:
P0: The Four Pillars of GAU: The Solar System and the Greater Averaged Universe.
P1 -- About the nature of matter between the stars:
The Cosmic Smog model for solar system formation, and the nature of 'Dark Matter'.
P2 -- About the origin of CMBR, Cosmic Microwave Background Radiation:
The Oort Soup as the real origin of Cosmic Microwave Background Radiation .
P3 -- How the microwave radiation from the Oort Soup opens up a new branch of Mid-IR astronomy:
Living In The Universe: (What CMBR tells us about Dark Matter, and much more).
P4: -- More about the Oort Soup, and how the Solar System fed from this in its billion-year history:
The Greater Averaged Universe (GAU) -- How the Solar System cannibalizes the Oort Cloud.
Inside The Earth -- The Heartfire Model. At: http://www.aoi.com.au/bcw/Heartfire/index.htm .
The Placid Universe Model -- Why the Universe is NOT Expanding, or, The real origin of CMBR, Cosmic Microwave Background Radiation. At: http://www.aoi.com.au/bcw/Placid/index.htm .
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