Natural star formation

[wattsr1]

Hi All,


This was going to be an essay on natural star formation. However, I became overwhelmed with information and so decided to put up a few pointers in a new thread and simply see what happens.

Maybe nothing will and the thread will fall away. Or perhaps someone will offer comment and the thread will take on a life of its own.

Jorge’s essay at http://www.theologyweb.com/campus/sh...d.php?t=136255 inspired this.

The post will be in note form. Hopefully it will therefore be easier to read.


THE QUESTION - “HOW DOES A STAR FORM?” IS NO DIFFERENT TO ...

... “how does a cloud form? How does a rain drop form?”

They can be looked philosophically, theologically, and/or a scientifically.

The Bible says as much about one as it does about the other.

Science says as much about the one as about the other.

Both have metaphysical underpinnings.

Science treats both as natural phenomena.

The Bible treats both as supernatural phenomena.

You are free to choose to reject the naturalistic scientific explanations for both phenomena.



A FEW REASONS FOR KNOWING THAT STARS MUST BE FORMING NOW

one

Some 60 years ago, that stars were still forming, was a non question. Hardly anyone considered it.

With the development of the theory that stars are natural fusion reactors, the idea that stars are forming now became an issue.

This is because some stars are massive. As such, they burn their fuel tens, to hundreds, to thousands to millions of times faster than our sun.

Because of this, they cannot have all been formed at the same time. Truly massive stars must have formed very recently compared to low mass stars such as our sun.


two

If stars are forming now, about the only places they can conceivably come from are from gas and dust clouds that are observed in space.

Low mass stars that are in theory young, are generally found in association with high mass stars as well as gas and dust clouds e.g. T-Tauri stars http://en.wikipedia.org/wiki/T_Tauri_star

T-Tauri stars are found in the region of the H-R diagram (see ref 3 - a star luminosity v star mass diagram, which reflects a star’s life from birth to death) where normal stars are not found. Models of stellar evolution show this region to be a region where stars should still be accreting mass, prior to becoming normal stars.

FU Orionis type stars are another example of stars which repeatedly flare up due to core collapse still occurring or due to accretion from a disk of material surrounding the star. (refs 1, 2). A Wiki link to these stars is http://en.wikipedia.org/wiki/FU_Orionis_star


A BASIC SCIENTIFIC EXPLANATION

Dense, cold, globular gas clouds exist. That is an observation. See http://en.wikipedia.org/wiki/Bok_globule and ref 4.

The scientific theory of cloud collapse, at its very basic level, relies on high school physics. (See ref 5)

It relies on a theorem called the “Virial Theorem” - http://en.wikipedia.org/wiki/Virial_theorem

Expressed in simple terms (more so that at the above link), we have, for a stable, gravitationally bound cloud:-

2K + U = 0

where:-

K is the total internal kinetic energy (energy of motion) of the cloud, dispersing the cloud,
U is the gravitational potential energy pulling the cloud in.

Thus, if 2K > |U| then the cloud will expand and dissipate because the internal motion of atoms will overcome the total pull of gravity keeping the cloud together. If |U| > 2K then the cloud will collapse because the pull of gravity will overcome any dispersion caused by random movements of the atoms making up the cloud. (There is a much bigger volume outside of the cloud than inside the cloud and so random movements have more likelihood of moving into the larger external volume than the smaller internal volume of the cloud).

It’s virtually impossible for a cloud to remain static in space. If the internal motions tending to push the cloud apart were exactly balanced by gravity tending to cause the cloud to collapse, all this would be destabilized by magnetic fields that twist their way through space, by the gravitational pull of a passing star, by the stellar winds which waft by, some of which can be quite violent.

So the cloud will either expand or collapse.

If the cloud begins to collapse, then it can continue to do so as long as it can radiate away the heat that builds up as it collapses. This kind of collapse is called isothermal collapse - the cloud temperature remains the same, more or less.

At the other extreme of isothermal collapse is adiabatic collapse at which the temperature of the cloud rises as it collapses, because it cannot radiate away the heat that builds up. If this situation remains, then the heat build up can prevent further collapse. (There are mechanisms for radiating away heat under adiabatic collapse, e.g. the presence of certain molecules and dust.)

Heat will prevent further collapse in the adiabatic situation until a point is reached at which there is enough energy to split the hydrogen molecules which make up most of the mass of the cloud. This process uses up heat energy and so the cloud will cool and begin to collapse again.

Eventually enough heat is generated through collapse that fusion of the hydrogen ions inside the core of the cloud switches on. This fusion counter-balances any further collapse and the object begins to settle down towards becoming a normal star.

Equations dealing with gas behavior and gravity which are reasonably well known to high school physics students can be substituted for K and U in the above mentioned virial equation, and various mathematical operations done to establish such things as a minimum mass to initiate collapse, a cloud radius for a given density at which collapse will begin, and a collapse time. The first two quantities were established by a British astronomer early last century, Sir James Jeans.


The above is the basic concept.

Naturally things in the real world are never as simple as a basic concept. For instance, as already mentioned, as a cloud collapses, so its temperature rises, and this works against further collapse. As a cloud collapses, it can become turbulent and this may or may not work against further collapse. (It may bring about the fragmentation of a cloud, leading to many individual collapses, and ultimately multiple star systems). Clouds are permeated by magnetic fields which become compressed during collapse, potentially bringing collapse to an end.

So in reality a lot more has to be considered than just high school maths and physics. Nevertheless, the above gives a conceptual idea of the main forces at play to get things started, one way (dissipation) or the other (collapse).

Given the real life complexities, very technical mathematical models are written, which are then solved by running them on computers.

The results are then used to match with observations. If the model does not match the observation then the question arises - exactly what physics has been left out - if any? The observation will often provide the clue. Sometimes, there may be nothing wrong with the model, it’s just that the observation target turns out to be inappropriate, and this is often determined at a later date. If physics has been left out and exactly what can be established, then the model is adjusted and further tests undertaken.

New instruments - telescopes, spectrographs and computers, allow the models to be refined and developed further.


THE ORIGIN OF LOW MASS STARS

This is reasonably well understood. There are lots of observations, feeding a reasonable number of models. Core collapse mentioned above, including turbulence and magnetic fields appear to explain the origin of low mass stars.

There are no real show stoppers.

Theory and observations are progressing at a reasonable rate. There are plenty of models and observations allowing astronomers to tease out the finer details of the process. New instruments - telescopes operating in the X-ray, infra red, visible, and radio parts of the spectrum are assisting, as are developments in computing. Although the theory mentioned above is relatively simple, in application, the equations are complex. When turbulence and magnetic fields are included, then the only possible way to solve the equations is via computers.


THE ORIGIN OF HIGH MASS STARS

”Massive stars are low in number but make a large contribution to the properties of galaxies. They are fundamental to the production of the heavy elements and to the energy balance of the interstellar medium. They attempt to regulate the rate of star formation on large scales through feedback via intense winds, radiation, and finally, through supernova explosions.

Most stars are born in the neighbourhood of a massive star. Therefore as viewed by the low-mass stars, massive stars are the influential, or interfering relatives. The life history of a star is thus not only determined by the conditions at birth (‘nature’) but also by the interaction with the environment in the formative years (‘nurture’). Massive stars can lead to the ejection from the cluster through their gravity or to a stunted growth through their feedback.

Their own origin remains a mystery. Moreover, massive stars should not even exist according to basic theory. This is because stars above 8 [times the mass of the sun] should ‘switch on’ their nuclear hydrogen burning during the accretion phase. Thus, their radiation pressure halts or even reverses the infall. This leads back to the paradox that the hot O and B stars should not exist.

Studies of how massive stars form are afflicted by confusion. ... ” (ref 6)



Regards, Roland



REFERENCES

1) G.H. Herbig, P.P. Petrov, and R. Duemmler, “High-Resolution Spectroscopy of FU Orionis Stars”, The Astrophysical Journal, 595:384-411, 2003 September 20

http://www.iop.org/EJ/article/0004-6...7842.text.html

2) C. Clarke, G. Lodato, S. Y. Melnikov and M. A. Ibrahimov, “The photometric evolution of FU Orionis objects: disc instability and wind–envelope interaction”, [u]Mon. Not. R. Astron. Soc.[/i] 361, 942–954 (2005)

3) http://en.wikipedia.org/wiki/Hertzsp...ussell_diagram

4) Bart J. Bok, “Globules and Star Formation”, The Moon and Planets, 19 (1978) 153-155

5) Bradley W. Carroll and Dale A. Ostlie, “An Introduction To Modern Astrophysics”, Adison-Wesley Publishing Company, 1996

6) Michael D. Smith, “The Origin of Stars”, Imperial College Press, London, 2004. Chapter 11.

[wattsr1]

Hi All,


This was going to be an essay on natural star formation. However, I became overwhelmed with information and so decided to put up a few pointers in a new thread and simply see what happens.

Maybe nothing will and the thread will fall away. Or perhaps someone will offer comment and the thread will take on a life of its own.

Jorge’s essay at http://www.theologyweb.com/campus/sh...d.php?t=136255 inspired this.

The post will be in note form. Hopefully it will therefore be easier to read.


THE QUESTION - “HOW DOES A STAR FORM?” IS NO DIFFERENT TO ...

... “how does a cloud form? How does a rain drop form?”

They can be looked philosophically, theologically, and/or a scientifically.

The Bible says as much about one as it does about the other.

Science says as much about the one as about the other.

Both have metaphysical underpinnings.

Science treats both as natural phenomena.

The Bible treats both as supernatural phenomena.

You are free to choose to reject the naturalistic scientific explanations for both phenomena.



A FEW REASONS FOR KNOWING THAT STARS MUST BE FORMING NOW

one

Some 60 years ago, that stars were still forming, was a non question. Hardly anyone considered it.

With the development of the theory that stars are natural fusion reactors, the idea that stars are forming now became an issue.

...

And of course, none of this assumes an ancient universe.

It no more assumes an ancient universe than we assume that atoms really exist when we build fusion reactors or make hydrogen bombs.

Just as we have evidence that atoms exist, so we have evidence that the universe is ancient. This evidence relies on well established theories from physics - optics, light, atomic theory, nuclear theory.

So naturally the idea of stars forming over millions of years sits within the framework of a universe we know to be ancient from other evidence.

Of course, if you think that the universe is 6,000 years old then we want your evidence for this, before you begin telling us of your theories about stars popping into existence out of nothing. And on that latter point too, we will also require evidence for the models you develop, explaining how this happens.


Of course you can say that you are right because you have some kind of revelation, and so evidence, logic and reasoned argument do not apply and can thus be dismissed.

But then, if you can do this, so can we. Even we atheists.



Regards, Roland

[One Bad Pig]

Eventually enough heat is generated through collapse that fusion of the hydrogen ions inside the core of the cloud switches on. This fusion counter-balances any further collapse and the object begins to settle down towards becoming a normal star.

This is generally true, but not for super-massive stars; Eta Carinae, IIRC, is so massive that fusion is not sufficient to halt its collapse.

[oxmixmudd]

This is generally true, but not for super-massive stars; Eta Carinae, IIRC, is so massive that fusion is not sufficient to halt its collapse.

Not sure where you get that. Perhaps you mean Eta Carinae is on the hairy edge in that it is about as big as a star can get. But that limit is defined by the point where the radiation pressure can't be compensated for by gravitational pull (Eddington limit). But this is an outward imbalance, not an imbalance toward collapse. As such it is very unstable. IIRC Eta Carinae is, as expected for such a large star, episodically blowing off mass at this point, not continuing to collapse. It is also expected to go supernova 'at any time' - in stellar evolutionary terms - and it is expected to produce a black hole in that event - perhaps that is what you mean?


Jim

[One Bad Pig]

Not sure where you get that. Perhaps you mean Eta Carinae is on the hairy edge in that it is about as big as a star can get. But that limit is defined by the point where the radiation pressure can't be compensated for by gravitational pull (Eddington limit). But this is an outward imbalance, not an imbalance toward collapse. As such it is very unstable. IIRC Eta Carinae is, as expected for such a large star, episodically blowing off mass at this point, not continuing to collapse. It is also expected to go supernova 'at any time' - in stellar evolutionary terms - and it is expected to produce a black hole in that event - perhaps that is what you mean?


Jim

Yeah, more or less. It's never really going to stabilize on the Main Sequence; the supernova will merely be the last episode of blowing off mass.

Sorry, it's been a while since my last astrophysics course.

[wattsr1]

Yeah, more or less. It's never really going to stabilize on the Main Sequence; the supernova will merely be the last episode of blowing off mass.

Sorry, it's been a while since my last astrophysics course.

Yes, Ox is correct by my understanding.

It's a star near the end of its life and a pretty rude one too. It's always belching.



Regards, Roland

[wattsr1]

Yes, Ox is correct by my understanding.

It's a star near the end of its life and a pretty rude one too. It's always belching.



Regards, Roland

A final one - just on the odd chance that Jorge might step in and actually discuss/argue the science.



Regards, Roland

[oxmixmudd]

A final one - just on the odd chance that Jorge might step in and actually discuss/argue the science.



Regards, Roland

Who knows what could happen if Jorge actually discussed science? It just might result in the end of the universe as we know it!

Jim

[wattsr1]

Hi All,

* Jorge has made contact. Bumping this, incase he wants to talk physics *

[lee_merrill]

Now there has been some progress, where it seems there is a mechanism by which massive star formation can be explained.

"Recent theoretical work has shown that the production of a jet and outflow clears a cavity through which much of the radiation from a massive protostar can escape without hindering accretion through the disk and onto the protostar. Present thinking is that massive stars may therefore be able to form by a mechanism similar to that by which low mass stars form."

C. F. McKee, J. C. Tan (2002). "Massive star formation in 100,000 years from turbulent and pressurized molecular clouds". Nature 416 (6876): 59–61.

R. Banerjee, R. E. Pudritz (2007). "Massive star formation via high accretion rates and early disk-driven outflows". Astrophysical Journal 660 (1): 479–488.

Blessings,
Lee

[Jorge]

Now there has been some progress, where it seems there is a
mechanism by which massive star formation can be explained.

***************************************************************

Allow me, LM ...

" ... there has been some progress, where it seems there is a purely natural
mechanism by which massive star formation can be explained remaining
strictly within the material realm."

Which is all fine and dandy AS LONG AS one first assumes that natural star formation
is possible. Furthermore, maybe (maybe!) today stars can form naturally (because,
for starters, there already exist other stars that assist in the process). This would not
in any way explain how the first stars were able to form unassisted.

"Recent theoretical work has shown that the production of a jet and outflow clears a cavity
through which much of the radiation from a massive protostar can escape without hindering
accretion through the disk and onto the protostar. Present thinking is that massive stars may
therefore be able to form by a mechanism similar to that by which low mass stars form."

C. F. McKee, J. C. Tan (2002). "Massive star formation in 100,000 years from turbulent and pressurized molecular clouds". Nature 416 (6876): 59–61.

R. Banerjee, R. E. Pudritz (2007). "Massive star formation via high accretion rates and early disk-driven outflows". Astrophysical Journal 660 (1): 479–488.

Blessings,
Lee

Some of the above was in the SciAM article that I posted about a while back.

Focus on the following : why are these people looking for HOW it happened / happens?
Isn't the first obvious question, does / can it happen?
But, see, they've already assumed that it can / has / does happen.
They HAVE to assume this. Why?
Because if it can't / hasn't then their entire Naturalistic worldview is shattered - kaput.

Mind you, as I have stated repeatedly (twice here), perhaps (maybe!) it can happen today.
That still leaves them clueless as to how the first stars came about.
But not to worry - if there's one thing that these people excel at, it's wild speculation.

Jorge

[Faid]

Focus on the following : why are these people looking for HOW it happened / happens?
Isn't the first obvious question, does / can it happen?
But, see, they've already assumed that it can / has / does happen.
They HAVE to assume this. Why?
Because if it can't / hasn't then their entire Naturalistic worldview is shattered - kaput.

Nice theory jorge. Let's try it again:


Focus on the following : why are doctors looking for HOW natural causes for disease happen?
Isn't the first obvious question, does / can it happen?
But, see, they've already assumed that it can / has / does happen.
They HAVE to assume this. Why?
Because if it can't / hasn't then their entire Naturalistic worldview is shattered - kaput.


Do you agree with the above, Jorge? If not, what's the difference?

I wonder if it's going to be another 10000 posts before you find the guts to address that question, with anything other than childish insults.

[oxmixmudd]

***************************************************************

Allow me, LM ...

" ... there has been some progress, where it seems there is a purely natural
mechanism by which massive star formation can be explained remaining
strictly within the material realm."

Which is all fine and dandy AS LONG AS one first assumes that natural star formation
is possible. Furthermore, maybe (maybe!) today stars can form naturally (because,
for starters, there already exist other stars that assist in the process). This would not
in any way explain how the first stars were able to form unassisted.


Some of the above was in the SciAM article that I posted about a while back.

Focus on the following : why are these people looking for HOW it happened / happens?
Isn't the first obvious question, does / can it happen?
But, see, they've already assumed that it can / has / does happen.
They HAVE to assume this. Why?
Because if it can't / hasn't then their entire Naturalistic worldview is shattered - kaput.

Mind you, as I have stated repeatedly (twice here), perhaps (maybe!) it can happen today.
That still leaves them clueless as to how the first stars came about.
But not to worry - if there's one thing that these people excel at, it's wild speculation.

Jorge

Jorge comes up with yet another denial of what is observed essentially anytime someone points a telescope at the Orion Nebula (which will soon be setting too early to observe and we'll have to wait till next fall to see it again).

Poor Jorge, his faith can only stand if he denies the majority of scientific knowledge gained since the 1700's. Of course, he can still use toasters and TV's, even computers I suppose (as long as they aren't simulating evolution or planet formation or star formation). But those pesky fossils and meteorite craters, and those nasty space telescopes and radiosotope dating labs - all that nasty stuff has to be stamped out and denied lest his version of what it means to believe in God come up short.

What a sad and pitiful excuse for faith that is. Poor Jorge. Poor, poor, Jorge.


Jim

[rogue06]

***************************************************************

Allow me, LM ...

" ... there has been some progress, where it seems there is a purely natural
mechanism by which Redwood Tree formation can be explained remaining
strictly within the material realm."

Which is all fine and dandy AS LONG AS one first assumes that Redwood Tree formation
is possible. Furthermore, maybe (maybe!) today Redwood Trees can form naturally (because,
for starters, there already exist other Redwood Trees that assist in the process). This would not
in any way explain how the first Redwood Trees were able to form unassisted.

Since nobody has ever seen a Redwood grow from a seed into a nearly 380' tree the same assertions you made concerning stars also applies for them. I mean how can anyone maintain that such a massive tree can grow from seeds so tiny that a million seeds weigh only eight pounds. And since they live for over 2000 years we can safely conclude the answer is "no" to the question "Were you there (to see the tree go from seed to fully mature adult)?" Obviously we accept that they grow from such tiny seeds because they must in order to fit in with our materialistic world view. Or as you put it:

But, see, they've already assumed that it can / has / does happen.
They HAVE to assume this. Why?
Because if it can't / hasn't then their entire Naturalistic worldview is shattered - kaput.

Dang Redwoods

[Jorge]

Jorge comes up with yet another denial of what is observed essentially anytime someone points a telescope at the Orion Nebula (which will soon be setting too early to observe and we'll have to wait till next fall to see it again).

Poor Jorge, his faith can only stand if he denies the majority of scientific knowledge gained since the 1700's. Of course, he can still use toasters and TV's, even computers I suppose (as long as they aren't simulating evolution or planet formation or star formation). But those pesky fossils and meteorite craters, and those nasty space telescopes and radiosotope dating labs - all that nasty stuff has to be stamped out and denied lest his version of what it means to believe in God come up short.

What a sad and pitiful excuse for faith that is. Poor Jorge. Poor, poor, Jorge.


Jim

************************************************************************************

The 'logic' of a fused circuit board and the integrity of a dung beetle. Poor Jim. Poor, sadly poor, Jim.

Jorge