Giant molecular clouds
A look at uniformitarian assumptions in star formation
Published: 15 March 2016 (GMT+10)
In almost any standard university astrophysics text you will find a chapter on star formation. Stars are alleged to have formed, and still do form, from giant clouds of molecular hydrogen gas. That is the standard party line. Thus it follows from standard big bang thinking that they were not created by the Creator on the fourth day of Creation week as outlined in Genesis 1, but naturally condensed out of gas (and dust) under the force of gravity only.
Nowadays you can read about dark matter as the seeds of the formation of galaxies and hence stars.1 But dark matter is still just a hypothetical substance. So how does star formation stack up without invoking such stuff? What physics can explain the alleged collapse of giant molecular clouds (GMC) to form stars? What were/are the typical explanations for star formation when dark matter was/is not assumed? And what unprovable uniformitarian assumptions are required?
To discover the answer to these questions I went to (and hence I quote extensively from) a standard 1996 first year university astrophysics text “An Introduction to Modern Astrophysics” (1st Edition) by Carroll & Ostlie,2 hereafter referred to as Carroll & Ostlie. I also looked at what the authors might have added in terms of overcoming some of the problems for star formation, a decade later, in their 2nd Edition, and found no substantive improvements.3,4
Carroll & Ostlie write:
“In some sense the evolution of a star is cyclic. It is born out of gas and dust that exists between the stars, known as the interstellar medium (ISM).”2 (emphasis in original)
This statement appears in one of the first paragraphs in Carroll & Ostlie (1st Ed.) chapter 12 titled “The Process of Star Formation”.5 But it is quite obvious that it could not possibly be true for the first stars, which allegedly formed in the early universe before there were any supernova explosions and therefore before any dust (and gases with atomic numbers greater than lithium) could be made and scattered into the interstellar medium. In such a case, the evolution (development) of the first stars could not be cyclic. After all it has a first-cause problem. And if, in any star-formation theory, you invoke supernovae to overcome the problem of collapsing the GMCs—from which it is alleged stars form—past the instability limit set by the Jeans criterion (see below), how do you propose those first stars overcame such a fundamental limitation?
When a neutral hydrogen atom performs a spin flip in its single proton nucleus it will emit very characteristic radiation at a wavelength of 21 cm or 1420 MHz.6 This microwave transition is seen in the cosmos both as emission and absorption lines. Astronomers use this signal to map the distribution and density of H I.7 Also from its absorption line spectra it may be used to estimate radial velocities of the H I clouds, and their temperatures (30 – 80 K); and their magnetic fields from the Zeeman effect.2
“Optically thick dust clouds shield hydrogen from sources of ultraviolet light radiation. One consequence of this shielding is that molecular hydrogen can exist without the threat of undergoing dissociation by UV photon absorption.”2
Therefore it is alleged that from this type of hydrogen—H2 molecules in enormously massive clouds—that we can expect to find the natural formation of new stars. But because of the nature of H2 molecules they do not emit any 21-cm radiation. They are very difficult to ‘see’,8 therefore other molecules are used as tracers. Because of the relative abundance (0.01%) of the carbon monoxide molecule (CO) it is commonly used as a tracer for the presence of molecular hydrogen.2 Here the assumption is made that molecular hydrogen is present and the CO tracer molecule is in collision with it, thus it may be used to derive the density and temperature of molecular hydrogen in the alleged clouds. See Fig. 1 for an example of a cloud from which no emissions are seen.
Thousands of giant molecular clouds (GMCs) are apparently known to exist in the spiral arms of our galaxy. No doubt this has been determined by the use of tracer gases. From those it has been determined that these enormous clouds of dust and gas typically have temperatures of about 20 K, masses up to 1 million solar masses and sizes on the order of 50 pc (or 160 light-years).
On the other hand there are small, dense, almost spherical clouds of molecular hydrogen known as Bok globules, with high opacity, low temperatures near 10 K, and relatively high densities. See Fig. 1. Their masses are in the range 1-1000 solar masses, and their sizes are around 1 pc (or 3.3 light-years).
“Infrared surveys of Bok globules have revealed that many, perhaps most, of these objects harbor young stars in their centers. Apparently Bok globules are active sites of star formation. Furthermore, the physical association between GMCs and very young O and B main-sequence stars suggests that star formation occurs in these regions as well.”2 (emphases added)
The use of the word ‘apparently’ here sets the stage for the arguments used in this chapter on star formation. The first sentence there states a fact except for the use of the word ‘young.’ The latter is a conclusion based on uniformitarian thinking that the story of cosmic evolution of stars is true. This is reinforced by the use of the word ‘apparently’ in the second sentence. There is no actual evidence of real-time observation of stars forming from the collapse of a GMC, but hey, if the ‘young’ hot stars are observed, as they are believed to evolve in a certain fashion along the so-called main-sequence, then why not? It is all good storytelling.
But in their sub-section titled “The Formation of Protostars” we should expect a clear statement of how a GMC collapses passed the Jeans instability limit. Now, protostars are alleged collapsed concentrations of hydrogen gas at a stage before nuclear fuel burning commences. Of this Carroll & Ostlie comment,
“One area where the picture is far from complete is in the earliest stage of evolution, the formation of pre-nuclear-burning objects known as protostars from interstellar molecular clouds.”2 (emphasis in original)
The question is asked,
“If molecular clouds are the sites for star formation, what conditions must exist for collapse to occur?”2 (emphasis added)
This is an essential question, one which needs answering for the materialist who rejects the Creator God.
“Sir James Jeans (1877–1946) first investigated this problem in 1902 by considering the effects of small deviations from hydrostatic equilibrium.”2
It was Jeans who developed the concepts that physicists are faced with when they assume a giant cloud of gas collapses to form a star. From energy conservation considerations, we can determine that as a cloud of gas is compressed it also heats up. The heating effect in turn increases the pressure within the cloud and it comes into hydrostatic equilibrium where the gravitational inward force is balanced by the outward pressure. No further collapse can occur and the cloud will be stable. Jeans however determined the minimum mass of a cloud with a certain density and temperature necessary to result in it spontaneously collapsing passed this Jeans stability limitation. This mass is known as the Jeans mass (MJ),
where K1 (and K2) is a constant, T is the temperature (in kelvins) and ρ the density of the cloud. This can be also expressed in the minimum radius necessary to collapse a cloud of a certain density ρ. The latter is called the Jeans length (RJ),
From Eq. (1) it is obvious that as the density of the cloud is increased with collapse the temperature of the cloud is increased (without some rapid cooling method; i.e. radiated away) and the required Jeans mass increases, as does the required Jeans length [Eq. (2)]. This runs counter to a collapse through the Jeans limit.
But Carroll & Ostlie, not wanting to be limited by details, use a simplified analysis, stating:
“Although several simplifying assumptions are made in the analysis, such as neglecting effects due to rotation and the galactic magnetic fields, it provides important insights into the development of protostars.”2 (emphasis added)
Without explaining how a giant molecular cloud gets to a certain size, temperature and density, they give an example of the core of an observed GMC that has a mass greater than the minimum Jeans mass. Then they state,
“Apparently the cores of GMC are unstable to gravitational collapse, consistent with their being sites of star formation.”2
Nowhere in this chapter on star formation do they explain how such a core of a GMC got that way, i.e. how it exceeded the Jeans mass. Then they state,
“In the case that the Jeans criterion for the gravitational collapse has been satisfied, the collapsing molecular cloud is essentially in free-fall during the first part of its evolution.”2,9(emphases added)
So from that point forward the cloud is already assumed to be collapsing, without any indication how it got that way. And it is assumed that the cloud is isothermal.
“This is true as long as the cloud remains optically thin and the gravitational potential energy released during the collapse can be efficiently radiated away.”2
It must be optically thin; meaning transparent to all radiation thus no heat is absorbed by the cloud. Thus the cloud remains at constant temperature during the collapse. More assumptions and more storytelling.
Later they discuss the case when the cloud reaches a point where all heat is retained by the cloud—the adiabatic stage—but this is considered well on the way to the nuclear burning stage.
From the assumption of an isothermal collapse of the cloud, it follows from Eq. (1) that the Jeans mass must decrease with an increase in density. Carroll & Ostlie then state:
“Given any initial inhomogeneities in density, after collapse has begun, sections of the cloud will independently satisfy the Jeans mass limit and begin to collapse locally, producing smaller features within the cloud.”2 (emphasis added)
Thus fragmentation of the cloud is alleged to occur. They ask: “But what stops the fragmentation process?”2 And remember previously the collapse was assumed to be isothermal to overcome heating of the cloud preventing further collapse. Now the opposite is assumed.
“Since we observe a galaxy filled with stars that have masses on the order of the mass of the Sun, the cascading fragmentation of the cloud cannot proceed without interruption. The answer to the question lies in our implicit assumption that the collapse is isothermal. …”2 (emphasis added)
The claim then it is that at some point in the collapse of the cloud it becomes optically thick and the temperature of the cloud rises preventing further collapse. In this case the Jeans mass increases thus preventing the collapse of any fragments smaller in mass to that value.
How do they determine the balance between the initial-stage isothermal collapse and the final-stage adiabatic collapse? Introduce an efficiency factor2 for the radiation of heat out of the cloud. It can accommodate whatever is needed.
This is just another tuning parameter, which is then determined to be true by the observational fact of the existence of sun-sized stars, in addition to the unstated assumption that stars do form naturally (somehow). It is just storytelling because the real problem of overcoming the Jeans mass and length limitation has not been discussed.
Rotation and magnetic fields
“Perhaps just as important to the questions of stability and the rate of collapse are the possible effects of rotation (angular momentum), the deviation from spherical symmetry, or the presence of magnetic fields. … Also, the interaction between the magnetic fields and charged particles could significantly influence the evolution of the cloud.”2 (emphasis added)
Angular momentum and magnetic fields are very significant problems to collapse of the initial GMC. Charged particles tend to fix magnetic field lines preventing collapse and though angular momentum effects are felt more in the equatorial plane, all evidence of our own solar system says that the angular momentum is mostly in the disk of planets, but physics says it should be in the central star as it collapses and spins up.
The authors admit their model is crude and that they have omitted some important aspects, like those listed above. Now, you might think that with computer modelling and solving the full complement of all equations that describe all the physics, an explanation of how the Jeans criterion is satisfied for the free-fall collapse of the cloud starting in the GMC. But we read next,10
“Consider a spherical cloud of approximately 1 M☉ and solar composition that exceeds the Jeans criterion.”11 (emphasis added)
So special pleading is used. The problem is ignored and the story states as the cloud collapses it becomes optically thick thus the cloud is adiabatically heated. This comes about through the presence of dust in the collapsing cloud forming a protostar at its core as the cloud comes into near hydrostatic equilibrium. The protostar should now be deep with a molecular cloud, but shielded from direct view by a cocoon of dust.2
This theoretical story then leads to observational verification. But are stars being observed collapsing? No, the astronomers look for as many stars as they can find in the above described situation. It is expected that that the new stars will be hard to find because of the relatively short timescale for their evolution from the GMC to a star (~10 million years for a 1 M☉star) with the structure expected by its main-sequence description.12
From this point on the description is largely limited by the examples that can be astronomically observed. By that I mean it is a form of ‘stamp-collecting’. You look for what you think are typical examples of objects in different stages of evolution. How is that any different from biological evolution and the interpretation of the fossil record as a multi-billion year history of their evolution from the simple to the complex? Yet at no time does any observer see any actual change, where a significant addition has been added to one animal to change it into another—in real time, I mean.
In light of this ‘stamp-collecting’, in discussion of T Tauri stage of star formation where there is a circumstellar accretion disk (Fig. 2), Carroll & Ostlie write:
“These accretion disks13 seem to be responsible for many of the characteristics associated with the protostellar objects, including emission line, mass loss, jets and perhaps even some of the luminosity variations. Unfortunately, details concerning the physical processes involved are not yet well understood.”2 (emphasis added)
Further ‘stamp-collecting’ this time using the Hubble Space Telescope has led to the conclusion that,
“The circumstellar disks, termed proplyds, appear to be protoplanetary disks associated with young stars that are less than 1 million years old.”2 (emphasis in original)
These disks, excluding the central star, have masses several times that of the earth. But how do they know those type of stars are less than a million years old? It is only by theoretical arguments that are far from being based on a rigorous model. As I have shown, in reality to achieve the latter, dark matter must be included in advanced computer simulations.1 This effectively amounts to fudging the physics. Lastly, Carroll & Ostlie write:
“A problem immediately arises when the effect of angular momentum is included in the collapse. Conservation of angular momentum arguments lead us to expect that all main-sequence stars ought to be rotating very rapidly, at rates close to breakup. However, observations show that this is not generally the case. Apparently the angular momentum is transferred away from the collapsing star.”2 (emphases added)
To solve this problem, magnetic fields are invoked in the disks of the young stars. They are anchored to convection zones and are theoretically used to couple out angular momentum from the central star. This has the effect of the slowing the star’s rotation by applying a torque to it. But it is special pleading. Exclude magnetic fields from the discussion of the initial collapse of the giant molecular cloud to form the star when they are a problem, but include them when you want to solve a different problem.
Carroll & Ostlie admit “… much work remains to be done.”2 And no doubt some advances have been made since the text was written, which I have addressed previously. Theorists tend to use dark matter to solve the most vexing problems. But that is like admitting that the problem is insoluble. Dark matter has been sought in all sorts of lab experiments now for the past 50 years and it has not been detected. But even if some form is, it still may not solve the problems of star formation because so much is needed, such that 85% of all matter in the solar system needs to be dark matter if the solar system and all other stars formed naturally and were not directly created by the Creator. But where is the stuff? Yet, without dark matter—the new god-of-the-gaps in astrophysics and cosmology—star formation was problematic and remains so. Far better is the explanation given in the Scriptures: “And God … made the stars also.” (Genesis 1:16)
References and notes
- Hartnett, J.G., Stars just don’t form naturally—‘dark matter’ the ‘god of the gaps’ is needed, September 2015; creation.com/stars-dont-form-naturally. Return to text
- Carroll, B.W. and Ostlie, D.A., An Introduction to Modern Astrophysics, Addison-Wesley Publishing Company, 1st Edition, 1996. Return to text
- A comparison with the following updated edition of this text indicates practically no differences in any substantive content in how the process of star formation is described. Carroll, B.W., and Ostlie, D.A., 2nd Ed. Return to text
- Carroll, B.W. and Ostlie, D.A., An Introduction to Modern Astrophysics, Pearson, Addison-Wesley, 2nd Edition, 2007. Return to text
- In Carroll & Ostlie 2nd Edition the same statement appears in chapter 12, “The Interstellar Medium and Star Formation”. All quotes from the 1st Edition are essentially repeated in the 2nd Edition except where indicated. Return to text
- And drop into a lower energy state. It will emit radiation in that case, but if in the lower energy state 21 cm radiation is absorbed the proton will be excited, and flip its spin, into the higher energy state. Emission and absorption lines are observed in the spectra of astronomical sources, as a result. This is illustrated in Fig. 2. Return to text
- H I is the name assigned to dissociated hydrogen atoms. Return to text
- H2 has no emission or absorption lines in the visible or radio part of the electromagnetic spectrum. The 21-cm line is in the radio part of the spectrum. Return to text
- This statement does not appear in Carroll & Ostlie, 2nd Ed., but instead a discussion is included on pp. 413–414, which introduces an external pressure on the cloud from the ISM. This is then given by the Bonner-Ebert mass, but it still involves an isothermal collapse and still requires the mass to have passed a critical condition. Return to text
- This statement does not appear in Carroll & Ostlie, 2nd Ed., but a discussion is included on pp. 420–421 on the effects of magnetic fields stating “…another possibility for triggering the collapse of a dense core. If a core that was originally subcritical were to become supercritical, collapse could ensue.”(p.421). This is in reference to an assumption on the magnetic fields permeating the cloud, that they are very small, which was left out of the 1st Edition text. But how does the cloud become magnetically supercritical? They don’t say. They simply write (p.421) “… but if the mass of the cloud exceeds MB[the Jeans mass when it includes the presence of a magnetic field]the cloud is magnetically supercritical and the force due to gravity will overwhelm the ability of the magnetic field to resist collapse.” So this is the same approach, but in this case now they assume the cloud mass is large enough to overcome both the outward pressure of the gas due to its temperature and also due to the magnetic field, which causes it to resist collapse. Return to text
- Ref. 2, p. 456.; 1 M☉ = 1 solar mass. Return to text
- Main sequence means the expected evolution trend in size, temperature and luminosity as a function of age, based on the assemblage and classification of thousands of stars. Return to text
- Disk of matter bound in orbit around the protostar onto which matter is accreted from the surrounding space. See also Hartnett, J.G., A ‘protoplanetary system’ in formation?, September 2015, biblescienceforum.com. Return to text