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om@umr.edu
2005-Aug-10, 11:34 AM
In a paper to appear in the 12 August 2005 issue of Science, UC-San Diego Professor Mark H. Thiemens and his associates, Vinai Rai and Teresa Jackson, will report that:

The Sun Was On more than 4.55 billion years ago, and UV light coming from that brightly glowing object became trapped in the isotopes, or forms, of sulfide found in four primitive groups of meteorites, the oldest remnants of the early solar system.

In a news report, Thiemens says that the slight excess of Sulur-33 in these sulfides "tells us for the first time that the sun was on, that there was enough ultraviolet light to do photochemistry".

These results are based on a technique Thiemens developed five years ago to reveal details about the Earth's early atmosphere from variations in the oxygen and sulfur isotopes embedded in ancient rocks.

The UCSD scientists used the early enrichment of S-33 in sulfides from the meteorites to estimate the intensity of the early solar wind and, hence, the intensity of the protosun.

What do you think of these new results?

Will this finding revive interest in the suggestion that clouds of gas do not collapse to form stars: Stars instead accrete on pre-existing objects [S.-S. Huang, “A nuclear-accretion theory of star formation” Astronomy Society of the Pacific 69, pp. 427-430 (1957)]?

With kind regards,

Oliver
http://www.umr.edu/~om

Duane
2005-Aug-10, 09:59 PM
What do you think of these new results?

Will this finding revive interest in the suggestion that clouds of gas do not collapse to form stars: Stars instead accrete on pre-existing objects [S.-S. Huang, “A nuclear-accretion theory of star formation” Astronomy Society of the Pacific 69, pp. 427-430 (1957)]?

Well, first of all I don't think the results in and of themselves say anything about how the solar system accreated. It says only that there was already at least UV light when the meteorites were formed.

Frankly, considering the progress surraounding planetary formation, I don't think that finding is all the surprising--in fact, IMO it actually enhances accretion theory.

A recent story here at UT (sorry, no time to find it) referrenced water as one of the constituants that seem to be the "glue" needed to begin the accretion process. Tp paraphrase from memory, the ignition of a proto-star intially melts water in the accretion disc, which shortly thereafter refreezes. During this process, other grains of material from the accretion disc "stick" to the refreezing water, thus beginning the building that leads to planets.

Another story also talked about carbon "tar" at Jupiter's distance ungergoing a similar process.

Thanks Dr Manuel, I think this finding adds another chapter to these other two stories, and does also help to support the theory of accretion.

om@umr.edu
2005-Aug-11, 04:43 AM
Originally posted by Duane@Aug 10 2005, 09:59 PM

What do you think of these new results?

Will this finding revive interest in the suggestion that clouds of gas do not collapse to form stars: Stars instead accrete on pre-existing objects [S.-S. Huang, “A nuclear-accretion theory of star formation” Astronomy Society of the Pacific 69, pp. 427-430 (1957)]?

1. Well, first of all I don't think the results in and of themselves say anything about how the solar system accreated. It says only that there was already at least UV light when the meteorites were formed.

2. I think this finding adds another chapter to these other two stories, and does also help to support the theory of accretion.
Hi, Duane.

1. You are right. The story says nothing about the accretion of planetary material*.

2. But it suggests that the Sun had already formed and was there burning brightly 4.55 billion years ago, at the start of the oldest geological record in planetary solids.

This raises the question whether the Sun might have been shining as a pre-existing object 4.55 billion years ago, that perhaps acquired at that time some of the same dust that accreted into meteorites and planets.

What do you think? Is that a possibility?

With kind regards,

Oliver
http://www.umr.edu/~om

*As you know, the standard solar model claims that the Sun neither lost nor gained mass by accretion.

lswinford
2005-Aug-11, 10:28 PM
I thought the standard solar model assumed accretion of a mostly hydrogen gas cloud around some point of the cloud's center of mass. Or are you saying that after the fusion fires sparked there was no accretion, everything there now was already there? And I'm assuming by accretion that you are ignoring the assumed insignificant capture of comets and meteor-like material. While the early solar system (as the moon so abundantly reminds us) was likely a very busy place, the economies of scale make the final residues of our accretion disk as comparatively inconsequential, right? (I still don't get the part where the lightest gas falls to the sun but rocks and denser stuff doesn't, but I'm the mental flyweight in this forum.)

Duane
2005-Aug-11, 10:59 PM
Originally posted by om@umr.edu@Aug 10 2005, 09:43 PM
2. But it suggests that the Sun had already formed and was there burning brightly 4.55 billion years ago, at the start of the oldest geological record in planetary solids.

This raises the question whether the Sun might have been shining as a pre-existing object 4.55 billion years ago, that perhaps acquired at that time some of the same dust that accreted into meteorites and planets.

What do you think? Is that a possibility?

*As you know, the standard solar model claims that the Sun neither lost nor gained mass by accretion.
Is it a possiblity? Well I suppose anything has a possibility, but frankly from all of the research being done in the field of planetary/solar formation, combined with the many many observations of star-forming regions, I would think this would be, at best, an anomalty.

Paper after paper I've read in Arxive, new reports, magazines, etc almost all suggest the general idea we have about the formation of stars and their accompanying planets is essentially correct. The devil, as always, is in the details.

The SSM, by the way, states clearly that the sun (and all stars) arose from the accumulation (ie accretion) of material in a dense cloud of mostly hydrogen. There is no evidence for formation in any other way, other than idle speculation and handwaving. There is even evidence of a neutron star gaining material from passing through an area of material that accumulated on its surface, such that it heated up by a few million degrees before beginning to cool again. That would certainly seem to discredit the idea of a rogue star somehow "finding" enough material to initial planet formation.

Could the sun have been shining 4.55 billion years ago? Certainly. That also fits in with the wealth of recent papers describing how the process of planetary formation begins. Again, it is the ignition of the proto-star, the T-Tauri phase of formation, that flash heats its environs to initiate the accretion process leading to planets.

Do you recall reading either of the articles I mentioned in my last post? If not, let me know and I will see if I can locate them for you.

Guest
2005-Aug-11, 11:04 PM
Originally posted by lswinford@Aug 11 2005, 10:28 PM
1. I thought the standard solar model assumed accretion of a mostly hydrogen gas cloud around some point of the cloud's center of mass.

2. I still don't get the part where the lightest gas falls to the sun but rocks and denser stuff doesn't, but I'm the mental flyweight in this forum.
Hi, Lswinford.

It will be interesting to see if the new paper revives interest in the suggestion that stars accrete on pre-existing objects instead of forming by the gravitational collapse of gas [S.-S. Huang, “A nuclear-accretion theory of star formation” Astronomy Society of the Pacific 69, pp. 427-430 (1957)]. Regarding your comments,

1. If the Sun formed by accretion, heavy elements would have fallen to the bottom and the object would have become chemically layered. The standard solar model claims that the early Sun was throughly mixed, with light elements like H and He as abundant inside the Sun as they are at the solar surface.

2. You are obviously are not a mental lightweight, since you noticed an almost unside-down sorting of heavy elements, with iron-rich planets above the Sun's hydrogen-rich surface.

With kind regards,

Oliver
http://www.umr.edu/~om

Guest
2005-Aug-11, 11:18 PM
Originally posted by Duane@Aug 11 2005, 10:59 PM
The SSM, by the way, states clearly that the sun (and all stars) arose from the accumulation (ie accretion) of material in a dense cloud of mostly hydrogen. There is no evidence for formation in any other way, other than idle speculation and handwaving. There is even evidence of a neutron star gaining material from passing through an area of material that accumulated on its surface, such that it heated up by a few million degrees before beginning to cool again. That would certainly seem to discredit the idea of a rogue star somehow "finding" enough material to initial planet formation.

Hi, Duane.

Referring to the Standard Solar Model, Aron Dar and Giora Shaviv wrote in "Standard Solar Neutrinos", The Astrophysical Journal 468, left column, middles of page 935 (1996):

"The model assumes a complete spherical symmetry, no mass loss or mass accretion, . . ."

If the Sun formed by accretion, how did it keep heavy elements floating at its surface, with the same heavy/light element mix that was in its core?

That seems difficult.

Oliver
http://www.umr.edu/~om

Duane
2005-Aug-11, 11:54 PM
Oliver, you are confusing the issue. First off, lets review their (Dar & Shiviv's) most recent work from May 25, 2005 STANDARD SOLAR NEUTRINOS (http://arxiv.org/PS_cache/astro-ph/pdf/9604/9604009.pdf)

To offer a couple of quotes:


They provide the most direct evidence that
the sun generates its energy via fusion of Hydrogen into Helium.


Without such an evidence it is quite important to improve
the standard solar model (which provides only an approximate de-
scription of the complicated sun) and to continue the search for a
standard physics solution to the solar neutrino problems.

Note here that their paper does not reference neutrino studies beyond 1995, before the osscilating neutrinos were found.


The standard solar model (e.g. Bahcall 1989 and references therein)
is a physical description of the sun based on the standard stellar
evolution equations, (e.g., Clayton 1968) which are used to cal-
culate its evolution from the premain sequence Hayashi phase to its
present state, using the best available input physics (initial con-
ditions, equations of state, nuclear cross sections, radiative opacities,
condensed matter effects). The model assumes a complete spherical
symmetry, no mass loss or mass accretion, no angular momentum gain
or loss, no differential rotation and a zero magnetic field through the
entire solar evolution . Thus, the assumed initial conditions are:
1. Fully convective, homogeneous, spherically symmetric protostar.
2. Initial mass of M⊙ = 1.99 × 1033gm.
3. No angular momentum, no differential rotation, no magnetic
field.
4. Initial chemical composition deduced from primitive meteorites,
the solar photosphere, the solar wind, the local interstellar gas
and the photospheres of nearby stars.

In other words, they are acknowledging that their model is an approximation and their comment of no mass loss or accretion relates to the condition of the sun after it reached premain sequence. In other words, they assume the sun already accreted the bulk of its mass before their predictions and modelling begins. They state clearly their model assumes the sun already has a mass of 1.99x 10^33gm. I cannot think of anything more explicit than that.

If I may be so bold, might I suggest that you consider the context of the quotes you reproduce in this forum? I also suggest you review the base models used by these two fine physicists, especially Bahcall's, as it is on his model outlining how the sun intially formed that they then extend their predictions through to the present.

Oliver, this is a common tactic that you use, and I have commented on it previously. You take a comment totally out of context, then reproduce it in such a way as to change the meaning the authors' are portraying. If, and I mean IF, you are going to quote someone, then at the least, ensure the quote accurately portrays the message the author is trying to convey.

How can I put this so that I convey my message clearly? To try and keep the conversation going, in those instances where you use a quote that is clearly taken out of context, or is based on older, revised information, I will endeavor to correct the quote or information to ensure the most recent and accurate findings are portrayed. Does that sound fair to you?

om@umr.edu
2005-Aug-12, 03:19 AM
Originally posted by Duane@Aug 11 2005, 11:54 PM

The standard solar model (e.g. Bahcall 1989 and references therein) is a physical description of the sun based on the standard stellar
evolution equations, (e.g., Clayton 1968) which are used to cal-
culate its evolution from the premain sequence Hayashi phase to its
present state, using the best available input physics (initial con-
ditions, equations of state, nuclear cross sections, radiative opacities,
condensed matter effects).

The model assumes a complete spherical symmetry, no mass loss or mass accretion, no angular momentum gain or loss, no differential rotation and a zero magnetic field through the entire solar evolution .

Thus, the assumed initial conditions are:
1. Fully convective, homogeneous, spherically symmetric protostar.
2. Initial mass of M? = 1.99 * 1033gm.
3. No angular momentum, no differential rotation, no magnetic
field.
4. Initial chemical composition deduced from primitive meteorites,
the solar photosphere, the solar wind, the local interstellar gas
and the photospheres of nearby stars.


Thanks, Duane, for providing the complete quote.

I only reproduced the section of that quote shown above in italics, since the issue is whether or not the Standard Solar Model claims the Sun formed by accretion.

The paper is very clear on this point: The Standard Solar Model assumes there was no mass loss or mass accretion.

As I asked earlier, If the Sun formed by accretion, how did it keep heavy elements floating at its surface, with the same heavy/light element mix that was in its core?

With kind regards,

Oliver
http://www.umr.edu/~om

cran
2005-Aug-12, 09:28 AM
My understanding was that the sun 'ignited' close to 6 billion years ago; the main accretionary phase of planet formation began about 4.56 billion years ago; that pre-solar minerals, including olivine, had been found and identified (in the past year or so) in meteoric material. :huh:


It will be interesting to see if the new paper revives interest in the suggestion that stars accrete on pre-existing objects instead of forming by the gravitational collapse of gas [S.-S. Huang, “A nuclear-accretion theory of star formation” Astronomy Society of the Pacific 69, pp. 427-430 (1957)]. You mean someone beat me to it? :( By two decades? :( damn&#33; >thinks< won&#39;t get famous for that one, then...

Has anyone else considered &#39;accretion-in-transit&#39; - the formation of objects larger than molecules in the turbulent, expanding supernova remnant nebula, which then become the foci for further accretion in the presolar nebula? :huh:

om@umr.edu
2005-Aug-12, 10:23 AM
Originally posted by cran@Aug 12 2005, 09:28 AM
1. My understanding was that the sun &#39;ignited&#39; close to 6 billion years ago; the main accretionary phase of planet formation began about 4.56 billion years ago; that pre-solar minerals, including olivine, had been found and identified (in the past year or so) in meteoric material.

2.
It will be interesting to see if the new paper revives interest in the suggestion that stars accrete on pre-existing objects instead of forming by the gravitational collapse of gas [S.-S. Huang, “A nuclear-accretion theory of star formation” Astronomy Society of the Pacific 69, pp. 427-430 (1957)]. You mean someone beat me to it? :( By two decades? :( damn&#33; >thinks< won&#39;t get famous for that one, then...

3. Has anyone else considered &#39;accretion-in-transit&#39; - the formation of objects larger than molecules in the turbulent, expanding supernova remnant nebula, which then become the foci for further accretion in the presolar nebula? :huh:
Thanks, Cran, for the messages.

1. Those ages seem to be about right. The r-process (rapid neutron-capture) made all elements heavier than Bismuth (Z = 83, A= 209) in a supernova explosion. By comparing the decay products of Th-232, U-235, U-238 and Pu-244, Kuroda and Myers showed that the supernova explosion occurred about 5 Billion years ago.

2. Sorry about that. But most "new" ideas in science are re-cycled old ones. Accretion of stars onto pre-existing objects (instead of gravitational collapse of a Hydrogen gas cloud) has great merit. I would urge you to look into that further.

3. That sounds close to our 1975 suggestion for "Local Synthesis of the Elements" instead of "Remote Synthesis of the Elements".

Additional findings on this subject up to 2000 are summarized in the Proceedings of a symposium organized by Nobel Laureate Glenn T. Seaborg and me, "Origin of Elements in the Solar System". Participants include leading astronomers, geo- cosmo-chemists and physicists, astrophysicists, nuclear chemists and physicists, etc. The 646 page Proceedings were published by Pluwer Academic/Plenum Publishers. It is probably available in your library or from the publisher.

My 55-page summary is here (http://web.umr.edu/~om/abstracts2001/origin_solar_system_book.pdf)

Would you like to speculate on the other issue, If the Sun formed by accretion, how did it keep heavy elements floating at its surface, with the same heavy/light element mix that was in its core?

Or the issue raised by Lswinford, How did the Sun manage to have iron-rich balls of dirt floating just above its surface? (The closest planet, Mercury, is about 60% iron.)


With kind regards,

Oliver
http://www.umr.edu/~om

cran
2005-Aug-12, 11:28 AM
Would you like to speculate on the other issue, If the Sun formed by accretion, how did it keep heavy elements floating at its surface, with the same heavy/light element mix that was in its core? To be quite honest, om@umr.edu, I&#39;m still coming to grips with how did the Earth manage to concentrate as much of the heaviest (or densest) elements in its crust that it seems to have ... when I&#39;m satisfied with some answers for that (I&#39;m rarely satisfied with a &#39;one and only way&#39; answer), then I might look at the other... <_<


Or the issue raised by Lswinford, How did the Sun manage to have iron-rich balls of dirt floating just above its surface? (The closest planet, Mercury, is about 60% iron.) You mean all those (relatively) tiny bits of flotsam inside the orbit of the first &#39;real&#39; planet? :huh:
Other than they were lucky enough to fall in just the right vector to avoid falling into the sun altogether; and that, overall in our system planetary density seems to decrease with increasing distance from the sun (modified somewhat by internal thermal considerations), suggesting to me that the vast bulk of ferrics and heavier starting material is either bubbling away inside the star (and perhaps accumulating for periods of time in little bits of charred scum at the upper margins of convection cells), or was slung out of the system altogether... I really don&#39;t think there&#39;s much I can offer there... :unsure:


3. That sounds close to our 1975 suggestion for "Local Synthesis of the Elements" instead of "Remote Synthesis of the Elements". So..... I&#39;ve been scooped again&#33; Rats&#33; :(

thanks for the link, om@umr.edu; I&#39;ll check it out soon...I promise...and I won&#39;t have a tantrum...I won&#39;t....I&#39;ll just whimper a little... :(

Guest
2005-Aug-12, 01:29 PM
Originally posted by cran@Aug 12 2005, 11:28 AM

Would you like to speculate on the other issue, If the Sun formed by accretion, how did it keep heavy elements floating at its surface, with the same heavy/light element mix that was in its core? To be quite honest, om@umr.edu, I&#39;m still coming to grips with how did the Earth manage to concentrate as much of the heaviest (or densest) elements in its crust that it seems to have ... when I&#39;m satisfied with some answers for that (I&#39;m rarely satisfied with a &#39;one and only way&#39; answer), then I might look at the other... <_<
Great, Cram.

Welcome to UT&#33;

I too am rarely satisfied with a &#39;one and only way&#39; answer, but that sometimes gets us into trouble.

I wish you well.

With kind regards,

Oliver
http://www.umr.edu/~om

Fraser
2005-Aug-12, 03:43 PM
SUMMARY: New research from the University of California, San Diego suggests that the cloud of gas and dust that would eventually turn into the Sun was already hot and glowing. The ultraviolet radiation blazing off this protosun played a big part in chemically shaping the early Solar System, including many of the organic compounds that make up life on Earth. The scientists detected it by finding evidence of high-energy solar wind in ancient meteorites.

View full article (http://www.universetoday.com/am/publish/protosun_was_shining_during_first_matter_.html)

What do you think about this story? Post your comments below.

StarLab
2005-Aug-12, 04:18 PM
Cool&#33; ;) B) First invention: sunscreen&#33; :P :lol:

Guest
2005-Aug-12, 04:35 PM
Hi, Fraser.

These are interesting results. We started a discussion of this under Other Stories, so you may want to transfer that thread here.

With kind regards,

Oliver
http://www.umr.edu/~om

suitti
2005-Aug-12, 05:40 PM
Will the last one to leave, please remember to turn the Sun off?

Duane
2005-Aug-12, 07:48 PM
The paper is very clear on this point: The Standard Solar Model assumes there was no mass loss or mass accretion.

Read it again Oliver. The paper very clearly says that the model outlined by Dar and Shiviv uses the initial starting parameters of a star that is already at premain sequence and has a mass of 1.99 x 10^33gm. They then begin to run the simulation assuming no further mass loss or gain.

Furthermore they also state their initial starting conditions are based on Bahcall&#39;s and/or Clayton&#39;s standard starting evolution equations--in other words Oliver, the accretion model of stellar evolution. I say again, read it all the way through, because your interpretation of the quote is completely, totally, unequivically wrong.


As I asked earlier, If the Sun formed by accretion, how did it keep heavy elements floating at its surface, with the same heavy/light element mix that was in its core?

This has been answered before, and I believe the same answer will suffice here.


At first glance that would seem to make sense. The reasons why not include:
- Iron and the heavier elements are more opaque to UV and higher energy photons, and are subject to more photon pressure than hydrogen and helium. This ejects them out of the sun rather than allow them to sink in.
- The quantity of material falling into the sun times its age is still only an undetectable fraction of the mass of the sun.

This is from Antoniseb in the Iron Sun discussion in May 2004 in answer to the very same question you asked here. Perhaps you do not recall reading the answer?


How did the Sun manage to have iron-rich balls of dirt floating just above its surface? (The closest planet, Mercury, is about 60% iron.)


You mean all those (relatively) tiny bits of flotsam inside the orbit of the first &#39;real&#39; planet?

I like cran&#39;s answer, couldn&#39;t have said it better myself. This has also been dealt with before Oliver. Perhaps you should refresh your memory by re-reading the Iron Sun Discussion thread.

lswinford
2005-Aug-12, 09:05 PM
3. No angular momentum, no differential rotation, no magnetic
field.


In Duane&#39;s list of "the assumed initial conditions", what then began the rotation and magnetic fields?

Using the normal &#39;accretion disk&#39; figure for star formation, that would provide its angular momentum. Using the also common picture of an early star with its "jet" action spewing and spinning, that too provides angular momentum (or did that which produces the assumed jet, thereby start the star to spinning from its stand-still posture?). These are common descriptive pictures used extensively here as the "accepted" scenario. Is your &#39;still sun&#39; therefore an intermediate step between the nebula mass consolidation and young-star stages?

Once it did begin to turn, by whatever mechanism that was, then we have the observable differentiation due to the graduated effect of centrifugal forces on the now-spinning star. In that way we see the varying speed march of sunspots based on lattitude.

Perhaps, the magnetic field developed as the fusion fires came up to some optimal range, completing the plasma ionic conditions that generated an electro-magnetic field reflecting the flow of the ionic fluxes? So, then at sometime the sun was not hot enough to provide a magnetic field, was that it?

Duane
2005-Aug-12, 09:14 PM
Well, it&#39;s not my list, it belongs to the authors. In reading the paper, I believe they took the starting conditions of the sun immediately before the T-Tauri phase, using all of the parameters available at that point. From there, they left the spin rate as it was calculated by Clayton, adding nothing more nor taking anything way from it.

In the real world, each of those forces would play a role. I think that it was simply too complicated for them to include all the real world forces that could act on the simulated solar evolutionary model.

Mass loss by solar wind/CME&#39;s, mass gain by meteorites, small deviations in spin, differential rotation, etc would all have very small effects on the sun (not zero by any means&#33;) and for the purpose of their modelling, I think they felt the deviations would be to small to have any real affect, and too hard to include in their model in any event.

It will be interesting to see how their "new" model will look with the discovery of how neutrinos osccilate.

cran
2005-Aug-12, 10:59 PM
In the real world, each of those forces would play a role. I think that it was simply too complicated for them to include all the real world forces that could act on the simulated solar evolutionary model. Yes, especially if they wanted some kind of result in their lifetime ... :)

Models have always been simplified expressions of the &#39;real thing&#39; ... each has had to include a number of starting assumptions and limited variables ... they have been evolving into more complex and detailed models as the means to run the calculations have improved (supercomputers) ... perhaps one day, some models or simulations might indeed be &#39;virtual&#39; copies of the &#39;real thing&#39; ... right down the last detail... :)

om@umr.edu
2005-Aug-13, 03:06 AM
Originally posted by Duane@Aug 12 2005, 07:48 PM

The paper is very clear on this point: The Standard Solar Model assumes there was no mass loss or mass accretion.

Read it again Oliver. The paper very clearly says that the model outlined by Dar and Shiviv uses the initial starting parameters of a star that is already at premain sequence . . .


Hi, Duane.

I looked again and I still do not find the part where "The paper very clearly says that the model outlined by Dar and Shiviv uses the initial starting parameters of a star that is already at premain sequence".

Would you tell us the page number where they say that?

Thanks,

Oliver
http://www.umr.edu/~om

Duane
2005-Aug-13, 03:18 AM
Oliver, what does this paragraph say to you?



The standard solar model (e.g. Bahcall 1989 and references therein)
is a physical description of the sun based on the standard stellar
evolution equations, (e.g., Clayton 1968) which are used to cal-
culate its evolution from the premain sequence Hayashi phase to its
present state, using the best available input physics (initial con-
ditions, equations of state, nuclear cross sections, radiative opacities,
condensed matter effects).

They start from the Hayashi phase (do you understand this term?) of a premain sequence star that has already reached the proto-star stage. They state unequivically that they begin with a star that has 1.99 x 10^33gm of mass.

In other words, they take the model from the T-Tauri stage through to the present.

om@umr.edu
2005-Aug-13, 04:58 AM
Hi, Duane.

I&#39;ll look for that quote tomorrow.

Is there any evidence that the Sun accreted 1.99 x 10^33 gm of mass but no angular momentum while photon pressure upward exactly countered the extra gravitational attraction on the heavier elements, leaving a pre-main sequence star of uniform chemical composition floating in a vacuum after all accretion ceased?

The news from UC-San Diego is that the Sun was brightly shining while the accretion disk was still there.

With kind regards,

Oliver
http://www.umr.edu/~om

Duane
2005-Aug-13, 05:06 AM
The paragraph is from the quote I put in earlier in this thread.

The starting conditions that the authors begin with are based on the proto-star stage calculations undertaken by Bachall and Clayton. They then take the sphere arising from those calculations and run it through their simulation.

What they do not do is add any forces over and above those calculations giving them the starting conditions of the proto-sun. So they do not take into account left over angular momentum, mass gain or loss, magnetic fields, differential rotation, or several other factors that make the modelling too difficult to perform with the computers they are using.

There may have been some heavier elements incorporated into the sun. By current reckoning, those heavier elements make up less than 1% of the sun&#39;s mass.

om@umr.edu
2005-Aug-13, 05:17 AM
Originally posted by Duane@Aug 13 2005, 05:06 AM
The paragraph is from the quote I made earlier in this thread.


What? This makes no sense.

First I reported that Aron Dar and Giora Shaviv wrote in "Standard Solar Neutrinos", The Astrophysical Journal 468, left column, middles of page 935 (1996):

"The model assumes a complete spherical symmetry, no mass loss or mass accretion, . . ."

You replied, "The paper very clearly says that the model outlined by Dar and Shiviv uses the initial starting parameters of a star that is already at premain sequence".

I inquired where "The paper very clearly says that the model outlined by Dar and Shiviv uses the initial starting parameters of a star that is already at premain sequence".

"Would you tell us the page number where they say that?

And you now say that you were quoting yourself?

Please explain.

Thanks,

Oliver
http://www.umr.edu/~om

Duane
2005-Aug-15, 04:09 PM
Oliver, your communication skills are sometimes atrocious&#33; :)

The quote is from the paper written by Dar and Shaviv and is one or two sentences before the line you quoted:

The model assumes a complete spherical symmetry, no mass loss or mass accretion, . . ."

It is part of the full quote I posted from them above. Get it now?

PS--you should be using their newer 2005 paper, not the one from 1996. I linked to it in the same post where I provided their complete quote.

om@umr.edu
2005-Aug-15, 05:49 PM
Thanks, Duane.

You are right.

My communications skills are atrocious&#33;

Thanks for clearing up that matter.

So now the main question remains:

Do you really think the Sun accreted 1.99 x 10^33 gm of mass, but no angular momentum, while photon pressure upward exactly countered the extra gravitational attraction on the heavier elements, leaving a pre-main sequence star of uniform chemical composition floating in a vacuum?

Doesn&#39;t that sound a little like hocus-pocus ?

Researchers at UC-San Diego just reported that the Sun was shining brightly 4.55 billion years ago, as the first solids were forming in the accretion disk.

With kind regards,

Oliver
http://www.umr.edu/~om

Duane
2005-Aug-15, 06:01 PM
Do you really think the Sun accreted 1.99 x 10^33 gm of mass, but no angular momentum, while photon pressure upward exactly countered the extra gravitational attraction on the heavier elements, leaving a pre-main sequence star of uniform chemical composition floating in a vacuum?

No. That is just the model that was used for this simulation.

lswinford
2005-Aug-15, 07:11 PM
I get it now, a little part anyways, when I read (http://www.blackwell-synergy.com/doi/abs/1...5.x? (http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2966.2005.09185.x?cookieSet=1)) in searching for the meaning of the "Hayashi phase".


The loss of angular momentum is plausibly the result of magnetic coupling with external gas during some epoch in the star&#39;s life. The same Maxwell stresses that brake the stellar rotation cause a precession of the instantaneous axis of rotation, so reducing the obliquity angle between the rotational and magnetic axes. A star that has suffered excess braking in the pre-main-sequence Hayashi phase may be magnetically spun up on the main sequence, with a simultaneous increase in the obliquity.

I guess I&#39;ll look a little further to try to digest that. Thanks for throwing me a bone I can chew on for a while.

om@umr.edu
2005-Aug-15, 11:55 PM
Originally posted by Duane@Aug 15 2005, 06:01 PM

Do you really think the Sun accreted 1.99 x 10^33 gm of mass, but no angular momentum, while photon pressure upward exactly countered the extra gravitational attraction on the heavier elements, leaving a pre-main sequence star of uniform chemical composition floating in a vacuum?

No. That is just the model that was used for this simulation.
Thanks, Duane.

You are right, "that is just the model", the model that supposedly explains the origin and operation of the Sun and all other stars in the cosmos.

One assumption of the model, that accretion preceded ignition of the Sun is contradicted by the finding that the Sun was shining brightly 4.55 billion years ago, when the first solids were forming in the accretion disk.

I had hoped that you might address some of the other assumptions that seem to be little more than wishful thinking - like a homogeneous, uniform distribution of elements throughout the newly formed Sun.

With kind regards,

Oliver
http://www.umr.edu/~om

Duane
2005-Aug-16, 06:38 PM
Originally posted by om@umr.edu@Aug 15 2005, 04:55 PM
One assumption of the model, that accretion preceded ignition of the Sun is contradicted by the finding that the Sun was shining brightly 4.55 billion years ago, when the first solids were forming in the accretion disk.

I had hoped that you might address some of the other assumptions that seem to be little more than wishful thinking - like a homogeneous, uniform distribution of elements throughout the newly formed Sun.


Oliver, you make two mistakes here. First of all, the model of accretion is not contradicted by the finding that the proto-star that became our sun was shining brightly in UV rays 4.55 billion years ago. If anything, and as I said earlier in this thread, the fact that the sun was shining so early enhances the accretion model.

It sometimes seems to me like you do not read what has been written previously. It was the comment I made that this finding seems to support the accretion model that got us started in this thread.

I say again--given the recent articles regarding water and carbon tar acting as "glue" to initiate the accretion process leading to planets, it seems to make sense that the flash-heating of the accretion disc surrounding a proto-star as it enters its T-Tauri phase would lead to the melting and refreezing of water and carbon tar, which appears to be a good bet for the start of accretion leading to planets.

Secondly, I am not at odds with what Dar and Shiviv are trying to model. It is an understandably simplified version of a very complex process. That they choose to keep their parameters simple does nothing to tarnish or lesson the accretion model of steller formation.

Larry, it appears that the Hayashi phase is the time immediately before the ignition of fusion in a proto-steller core. It is the point when the star has already accreted the bulk of it&#39;s mass and is beginning the process of moving from protostar to main-sequence star.

lswinford
2005-Aug-16, 06:50 PM
Thanks for introducing me to the term and this additional step in the process.

Duane
2005-Aug-16, 06:59 PM
Always pleased to help :)

om@umr.edu
2005-Aug-17, 12:42 PM
Originally posted by Duane+Aug 16 2005, 06:38 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Duane &#064; Aug 16 2005, 06:38 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-om@umr.edu@Aug 15 2005, 04:55 PM
One assumption of the model, that accretion preceded ignition of the Sun is contradicted by the finding that the Sun was shining brightly 4.55 billion years ago, when the first solids were forming in the accretion disk.

I had hoped that you might address some of the other assumptions that seem to be little more than wishful thinking - like a homogeneous, uniform distribution of elements throughout the newly formed Sun.


1. Oliver, you make two mistakes here. First of all, the model of accretion is not contradicted by the finding that the proto-star that became our sun was shining brightly in UV rays 4.55 billion years ago. If anything, and as I said earlier in this thread, the fact that the sun was shining so early enhances the accretion model.
. . . .
2. Larry, it appears that the Hayashi phase is the time immediately before the ignition of fusion in a proto-steller core. It is the point when the star has already accreted the bulk of it&#39;s mass and is beginning the process of moving from protostar to main-sequence star. [/b][/quote]
Thanks for the clarification, Duane.

1. I agree that "the model of accretion is not contradicted" by the finding that our sun was shining in the middle of an accretion disk, 4.55 billion years ago.

The standard solar model is contradicted by this finding.

The UC-San Diego finding is contrary to the standard solar model&#39;s claim that all accretion ceased before the Sun ignited.

2. I agree that the Sun formed by accretion. However, accretion up to "the time immediately before the ignition of fusion" :

a.) Would produce a chemically layered star, with light elements floating on top, contrary to the uniformily mixed star required for the standard solar model, and

b.) Would never have the star brightly shining in the middle of an accretion disk.

With kind regards,

Oliver
http://www.umr.edu/~om

lswinford
2005-Aug-17, 06:21 PM
2. I agree that the Sun formed by accretion. However, accretion up to "the time immediately before the ignition of fusion" :

a.) Would produce a chemically layered star, with light elements floating on top, contrary to the uniformily mixed star required for the standard solar model, and

b.) Would never have the star brightly shining in the middle of an accretion disk.


I suspect that it would be hard to get all that hydrogen and helium to coalesce into a body if either the gas or the body (proto-star, proto-planet) were hot. Really heavy mass centers, such as black holes or other very dense masses, might counteract the diffusive mechanical properties of hydrogen and helium in a low pressure (dare I say &#39;no pressure&#39;?) space environment.

To gather the mass, its got to be cold. Obviously, at somepoint it doesn&#39;t stay cold. By that time, however, the particulate traffic is essentially going the other way as solar matter is boiled out (solar wind) or ejected (CME).

Whether the accretion was finished or still in process when the fusion fires ignited, well that leaves the possibility for some of the accretion to continue, but that would certainly have to be the heavy mass materials that somehow was too slow to fall before the two lightest gasses did (perhaps they had further to fall and were but just the tail end of the accretion process).

I&#39;m guessing now, but would the Hayashi phase happen right after the star fires up and before the radiative pressures change the flow of light elements? Or does the braking of the star&#39;s rotation thereby affect the spiral flow, sort of back pressure, that induces a "stall" upon the descending matter? (I turn my airplane&#39;s nose up, but decrease my speed, it stalls at some point and begins to fall when that which supports my upward trajectory are insufficient to overcome the downward forces of gravity). But then if the star was shining brightly, that energy would diminish the tendency of hydrogen and helium to fall into the ball. Maybe it just wasn&#39;t shining a lot.

Duane
2005-Aug-17, 06:43 PM
Originally posted by om@umr.edu@Aug 17 2005, 05:42 AM
[Thanks for the clarification, Duane.

1. I agree that "the model of accretion is not contradicted" by the finding that our sun was shining in the middle of an accretion disk, 4.55 billion years ago.

The standard solar model is contradicted by this finding.

The UC-San Diego finding is contrary to the standard solar model&#39;s claim that all accretion ceased before the Sun ignited.

2. I agree that the Sun formed by accretion. However, accretion up to "the time immediately before the ignition of fusion" :

a.) Would produce a chemically layered star, with light elements floating on top, contrary to the uniformily mixed star required for the standard solar model, and

b.) Would never have the star brightly shining in the middle of an accretion disk.

With kind regards,

Oliver
http://www.umr.edu/~om

1.) The standard solar model is contradicted by this finding.

I disagree completely. The SSM says that the sun accreted its mass from a well mixed cloud that was 99.8% hydrogen, to the point where the gravitatinal pressure in the center of the accretion disc was high enough to ignite nuclear fusion. At the point of ignition, the protostar was still surrounded by its accretion disc, such that some 0.1 billion years or so after the beginning of the collapse of the cloud that formed our sun, it would have shone brightly in UV, irradiating the material still in the disc.

You rely too heavily on the Dar and Shiviv model in your argument.

Further, the SSM does not say all accretion ceased before the sun ignited. Where do you get that from anyway? I&#39;ve heard this from you a few times now, and it continues to baffle me how you could arrive at a conclusion like that, when the whole basis of the SSM is the accretion of mass that eventually ignited as a star, and the accretion of the disc the star was embedded in to form planets. Again, you rely too heavily on one single simplified model that does not at any point say accretion stopped.

Read the paper again Oliver, because you are not getting it. The model you use for your argument against the SSM is one model that takes the protosun from the point of ignition forward within some very tight, well explained parameters. It is a simplified model Oliver, nothing more.


a.) Would produce a chemically layered star, with light elements floating on top, contrary to the uniformily mixed star required for the standard solar model, and

So what? The cloud it formed from is made up of about 99.8% hydrogen. There is evidence of metals in the sun, no one is saying there is none Oliver. It is just that the amount is so small it is of little consequence.


b.) Would never have the star brightly shining in the middle of an accretion disk.

Bullcrap Oliver. It is the brightly shining star that eventually blows the remaining gases in the accretion disc away, thus allowing the star to emerge from the cloud it formed in and show itself to the universe. Where do you come up with this stuff?

Finally, lets talk a little bit about the SSM, as you seem so incenced (and obsessed) about it. The SSM is simply a model that uses a 1 solar mass object that has the same luminosity, density and mixing length parameters as those observed in the sun. It is only a benchmark, a starting point from which more complicated attributes (such as magnetism, differencial rotation, altered mixing length parameters, etc) can be modelled to see how well they actually match up with the observations of the REAL sun.

It IS NOT claimed by ANYONE that the SSM is a be all and end all, nor does anyone claim the model is static. Your claims to the contrary are just noise and handwaving Oliver.

You talk about your so called Major Space Aged Observations, or whatever you call them now, without taking the time to have even one single parameter of your theory modelled against the observations of the real sun. You know, obsevations, as in looking at the damned thing.

That is enough for this thread for now. If you want to talk more about the SSM and it&#39;s implications on how we look at the REAL sun, start another thread.

Duane
2005-Aug-17, 07:21 PM
Obviously, at somepoint it doesn&#39;t stay cold.

Exactly L. As the mass accretes in the centre of the cloud, gravitational pressure released by the contracting mass begins to heat the central core. The gravitational energy is released in two ways (well, there is some disagreement on this point, see Virial Theorem (http://astrosun2.astro.cornell.edu/academics/courses/astro201/vt.htm)), half to heat the central core and half radiated away. Once the heat reaches the right temperature, nuclear fusion begins, and the star ignites.

The radiated gravity pressure may be strong enough to push metals (ps--the solar physics term "metals--anything heavier than H & He) in the contracting core away, but that is just a guess on my part. I think radiation and photon energy probably have more to do with that, but again, just a guess.


but would the Hayashi phase happen right after the star fires up and before the radiative pressures change the flow of light elements? Or does the braking of the star&#39;s rotation thereby affect the spiral flow, sort of back pressure, that induces a "stall" upon the descending matter?

Whew&#33; Ok, as I understand it, the Hayashi phase happens at the point just before fusion starts. I think the radiative pressure arising from the gravitational energy release is already in full operation, and the Hayashi Phase begins right at the point, or just immediately before the point, when the energy released by the protostar changes from gravitational to fusion.

I don&#39;t think the descending matter stops, because immediately after fusion begins the star enters the T-Tauri phase, and polar jets form. It seems to make sense that the jets form prior to the T-Tauri phase, but I don&#39;t think that has been modelled, or even discussed. Regardless, the jets begin the process of removing excess unaccreted matter from the accretion disc, blasting it out into the ISM or raining it back into the disc at some distance away, depending on the size of the new star.

Guest
2005-Aug-17, 09:02 PM
Originally posted by Duane@Aug 17 2005, 06:43 PM
1. I disagree completely.

2. It IS NOT claimed by ANYONE that the SSM is a be all and end all, nor does anyone claim the model is static.
Hi, Duane.

1. I guess we will just have to agree to disagree. You think the UC-San Diego finding supports the Standard Solar Model; I find it in conflict with Dar and Shiviv&#39;s description of the Standard Solar Model, but there is a disclaimer . . .

2. The Standard Solar Model "is not static." It has many adjustable parameters, as could be seen by the recent flury of activity following a report that the Sun contains about 30% less metals than previously thought.

Thank you for allowing us to have this discussion on the unlikely possibility of an observation being in conflict with the Standard Solar Model.

With kind regards,

Oliver
http://www.umr.edu/~om

lswinford
2005-Aug-18, 05:51 PM
I guess I was confusing the T-Tauri jets with those of pulsars, which were indicative of spin, and a great spin at that. With the T-Tauri jets being a pressure outflow/outlet from the stellar collapse/condensation, most of the descriptions I&#39;ve heard were of an early and brightly burning star.

I used to picture, before this article and discussion, essentially that &#39;the dust had settled&#39; and that besides a random assortment of dust and rock, most everything else had either been found or encorporated into the planets/protoplanet centers of gravity--the solar system essentially defined--and the remains of the accretion disk essentially the left-over trash from the party as the bulk of stuff had already found a home (sun, planets, moons, asteroid camps).

Still, with the scale of solar effluent, ranging from the early T-Tauri jets to today&#39;s solar winds and CMEs, it almost seems that the vacuum of space in our solar system would be less vacuuous, especially since there&#39;s been some four billion years of it. I guess part of the problem may lay in our illustration of accretion disks as dusty clouds (we&#39;ve had some pictures here in UT recently to that effect).

Trying to reimagine (by picturing a diffusing, or unpacking, of our sun, as if running the film backward) the solar system space as an essentially clear (hydrogen and helium being colorless gasses) cloud, particularly considering how little the proportional share of discernable heavy materials. It makes me wonder if there be much to look at, as if we would be able to spot something like our early stages of stellar coellescence. The pictures of bright and busy stellar nurseries in Orion&#39;s belt, for instance, seem so removed from our neighborhood.

I almost wonder which of the two possible conditions rule: (1) that we are so far gone from our nursery environment that we don&#39;t really have the original data to properly judge the conditions of our origin, or (2) our origins are singular, comparatively unique, and what is around us now is all that remains but is the basis to deduce our stellar beginnings. If it were #1, it might be fun in the future to aim probes like the Voyagers so that they could sample the &#39;bread crumbs&#39; we&#39;ve been leaving behind on our trajectory throught the galaxy. :huh:

This reminds me of evolution discussions of a few decades ago: we resemble gorillas more than chimps in these (x) ways; no, we resemble chimps more than gorillas in these (y) ways; no, we are different from both in these (z) ways. ;)

cran
2005-Aug-18, 11:54 PM
I almost wonder which of the two possible conditions rule: (1) that we are so far gone from our nursery environment that we don&#39;t really have the original data to properly judge the conditions of our origin, or (2) our origins are singular, comparatively unique, and what is around us now is all that remains but is the basis to deduce our stellar beginnings. If it were #1, it might be fun in the future to aim probes like the Voyagers so that they could sample the &#39;bread crumbs&#39; we&#39;ve been leaving behind on our trajectory throught the galaxy. There&#39;s a very good chance that you are close on both... B)

Star-birthing nebaulae not only include the closely packed, highly chaotic regions of new stars ... but some have clearly seen protrusions called &#39;fingers&#39;, which include more than enough mass to form a decent solar system (there are some truly massive ones in the Eagle nebula called &#39;the Pillars of Creation&#39;), and which are in the process of leaving the "nest" and evolving. The next step seems to be evaporating gaseous globules (or EGGs), which look like &#39;fingertips&#39; which have completely broken away from the main nebula ... and the EGGs seem to evolve into &#39;proplyds&#39; (protoplanetary disks). :)

om@umr.edu
2005-Aug-19, 04:59 AM
Originally posted by lswinford@Aug 18 2005, 05:51 PM
I almost wonder which of the two possible conditions rule: (1) that we are so far gone from our nursery environment that we don&#39;t really have the original data to properly judge the conditions of our origin, or (2) our origins are singular, comparatively unique, and what is around us now is all that remains but is the basis to deduce our stellar beginnings.* If it were #1, it might be fun in the future to aim probes like the Voyagers so that they could sample the &#39;bread crumbs&#39; we&#39;ve been leaving behind on our trajectory throught the galaxy.* :huh:
Perhaps neither condition rules.

What rules is a fear to examine without bias findings that were totally unexpected.

For example:

a.) The FUN (Fractionation + Unknown Nuclear) isotopic amomalies that Gerry Wasserburg and many others found in meteorites means this:

Nucleosynthesis isotope anomalies were mysteriously embedded in mass fractionated material when the solar system formed. Why ?

b.) The presence of the distinctive levels of O-16 in six classes of meteorites and planets that Robert Clayton identified (and another recently found also in the Sun) means this:

Chemical and isotope variations were linked over planetary distances in material that formed the solar system. Why ?

The trail is clear. But it leads in the "wrong" direction.

With kind regards,

Oliver
http://www.umr.edu/~om

cran
2005-Aug-19, 07:58 AM
:huh: I think I liked my answer better :blink:

Duane
2005-Aug-20, 06:41 AM
What rules is a fear to examine without bias findings that were totally unexpected.

No, what rules is the desire to first see if current theories can explain the anomalty. In this case, they can.


a.) The FUN (Fractionation + Unknown Nuclear) isotopic amomalies that Gery Wasserburg and many others found in meteorites means this:

Nucleosynthesis isotope anomalies were mysteriously embedded in mass fractionated material when the solar system formed.

Gerald (Gerry) Wasserburg (http://www.gps.caltech.edu/faculty/wasserburg/wasserburg.html) you mean? Of Cal Tech, yes? The same person who discovered the first circumstellar hibonite S-H5323 (CaAl12O19) found in a meteorite? The one who proposes that the hibonite originated in a Asymptotic Giant Branch Star prior to the formation of the solar system?

Perhaps you could link us to the paper where he reached the conclusion that the isotope anomalties were "mysteriously embedded" as you state? Or is that your conclusion?

I note Dr Wasserburg&#39;s interpretation of how our sun formed:


The parent cloud of the protosun contains gas and preserved dust grains from several generations of stars formed in different molecular clouds, as well as that added to the local inventory by "local" sources. All of these diverse stellar sources provide nuclei with short-, intermediate-, and long-lifetime nuclei. Each is produced over different time scales.


b.) The presence of the distinctive levels of O-16 in six classes of meteorites and planets that Robert Clayton identified (and another recently found also in the Sun) means this:

Chemical and isotope variations were linked over planetary distances in material that formed the solar system. Why ?

I&#39;m sorry, I don&#39;t understand the question. Could you please elaborate?

om@umr.edu
2005-Aug-21, 06:34 AM
Originally posted by fraser@Aug 12 2005, 03:43 PM
SUMMARY: New research from the University of California, San Diego suggests that the cloud of gas and dust that would eventually turn into the Sun was already hot and glowing. The ultraviolet radiation blazing off this protosun played a big part in chemically shaping the early Solar System, including many of the organic compounds that make up life on Earth. The scientists detected it by finding evidence of high-energy solar wind in ancient meteorites.

View full article (http://www.universetoday.com/am/publish/protosun_was_shining_during_first_matter_.html)

What do you think about this story?* Post your comments below.
Hi, Fraser.

I understand that the 15 August 2005 issue of Geochimica et Cosmochimica Acta has two papers about isotope heterogeneities from element synthesis and short-lived radioactivities in the accretion disk around the brightly shining Sun 4.55 billion years ago:

1. A paper from Washington University provides new data on anomalous oxygen isotopes in spinels from meteorites.

Robert Clayton and associates at the University of Chicago discovered "Strange" Oxygen in meteorites 32 years ago [R. N. Clayton et al. "A component of primitive nuclear composition in carbonaceous meteorites", Science 182, 485-488 (1973)].

2. A paper from the University of Manchester reports the finding of radiogenic Xe-129 and "Strange" abundances of the other eight xenon isotopes in tiny diamonds recovered from unequilibrated ordinary chondrites.

Edward W. Hennecke, Dwarka Das Sabu and I discovered "Strange" Xenon in meteorites 33 years ago ["Xenon in carbonaceous chondrites", Nature 240, 99-101 (1972)].

It is difficult to imagine how a homogeneous Sun might be formed from such a heterogeneous accretion disk.

With kind regards,

Oliver
http://www.umr.edu/~om

om@umr.edu
2005-Aug-25, 01:08 PM
This was an unnecessary provocation. I have deleted it.

Oliver
http://www.umr.edu/~om

antoniseb
2005-Aug-26, 02:19 PM
Cran,

I am closing this thread for now. If you want to discuss Dr. Manuel&#39;s view of the solar system, you will need to do it in a thread in the alternative theories section. This discussion cannot be done in the main Story Comments section.

antoniseb
2005-Aug-26, 03:43 PM
Recent events have freed me to re-open this topic.

Duane
2005-Aug-26, 03:49 PM
cran, because of your interest and the obvious intellegence you bring to bear on this discussion, I am opening a new thread in the alternative theories section. Should you wish to, you may continue your queries of Dr Manuels unorthodox theory there.


The link to the split-off topic: http://www.universetoday.com/forum/index.p...?showtopic=8712 (http://www.universetoday.com/forum/index.php?showtopic=8712)

cran
2005-Aug-26, 10:13 PM
Understood guys, and I do apologise for being sidetracked like that... forgot where I was (kid in a candy store syndrome)... :(

I will try to be more careful in future.