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Old 26-April-2008, 05:23 PM
William William is offline
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Default Milky Way’s Galactic Core, Stellar “Paradox of Youth”

Milky Way’s Galactic Core, Stellar “Paradox of Youth”

The subject of this thread is what is known as the “paradox of youth” problem which is how to explain the recent discover of very young, massive, short lived stars that are located very, very, close to the galactic core. The “paradox of youth” problem is that the stars in question have a lifetime that is at most 100 MM years and it is very difficult to create a gas cloud with sufficient density to enable that number of very young stars to form so close to the galactic core. Half of stars in questions are located in three tight clusters of stars that are estimated to be 0.5 MM years old. There is no evidence of current star formation in the locations where the young stars in question are found which is puzzling, but perhaps not unexpected as simulations indicate that it is very difficult to get gas clouds to form that close to the Milky Way’s core massive compact object.

http://arxiv.org/abs/astro-ph/0508106v1

The following are excerpts from the above review paper “Stellar Processes Near the Massive Black Hole in the Galactic Center” by Tal Alexander which summarizes the observations and different hypotheses that have been developed to try to explain this paradox.

Quote:
About half of the young stars in the region are found today in three particularly massive, young (.5 Myr) clusters: The Quintuplet (∼30 pc from the center in projection, M ∼10^4M⊙…, The Arches (∼30 pc from the center in projection, M &10^4M⊙, R∼0.2 pc, …, and the central cluster around the Milky Way's massive black hole (Figer 2003). The three clusters contain in total hundreds of MS O-stars, tens of Wolf-Rayet (WR) stars and a few luminous blue variable stars (§2.2), which are ∼10% of all the massive stars (initial mass>20M⊙) in the entire Milky Way Galaxy.
Quote:
It has proved difficult to find a satisfactory explanation of how they could have formed so close to the massive black hole, or alternatively, of how they could have migrated inward from farther away in the course of their short lifespans. This is the so-called “paradox of youth”. The question applies to any of the young stars in the inner parsec, but particularly so to the central cluster of the “S-stars”, which exist a mere few hundredths of a parsec from the massive black hole. The problem of the young stars has become one of the major outstanding issues in galactic core research.

Quote:
The young population in the inner ∼1 pc is often loosely described as the “OB-stars”. This general designation can be misleading, as it fails to convey the significant systematic differences that exist in the population. An important open question is the nature of the connection, if any, between the S-stars inside ∼0.04 pc and the luminous emission line stars further out, on the 0.04–0.4 pc scale. While it is plausible to assume that these are different components of the same parent population, it should be noted the two groups have distinct locations, kinematics and stellar properties. The stars detected so far in the two young star disks at p∼1”–10” are luminous OB supergiants, giants and WR stars of various types (Genzel et al. 2003b; Paumard et al. 2001; Paumard et al. 2004).
Quote:
The solutions proposed so far for the riddle of the young stars (see reviews by Genzel et al. 2003b; Ghez et al. 2005) fall into three main categories: unusual modes of star formation near the Milky Way's massive black hole; rejuvenation of old stars from the local population; and dynamic migration or capture from farther out, where stars can form. While each has some attractive features, none is quite satisfactory. The paradox of youth remains unsolved at this time.
Comment:
The overall universe is estimated to be 13.7 billion years old. Our galaxy is one of the oldest galaxies in the universe and is estimated to be 13.6 billion years old. An interesting question is how to explain why the mass of the compact massive object at the centre of the Milky Way SgrA* is only 3.6x10^6 solar masses.

(The abbrievation “SgrA*” is short for Sagittarius A* is used to designate the Milky Way’s black hole. The Milky Way’s black hole (BH) is located in the constellation Sagittarius and is designated as “Sagittarius A*”.)

The Milky Way galaxy formed during the crowded early times in the universe and would therefore have opportunities for multiple mergers with other galaxies, in addition to time to accrete its own very massive compact objects. The current theory of galaxy formation hypothesizes that all galaxies that have a central massive object at their core have gone through a quasar phase. It is therefore natural to compare the Milky Way to galaxies that going through their “quasar phase’. Quasars at z=2, for example when the universe has only 3.3 billion years old, have an average black hole mass in the order of 10^8 to 10^9 solar masses, a hundred to a thousand times larger than the Milky Way’s compact object.
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Old 26-April-2008, 05:59 PM
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Veeger Veeger is offline
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Ok - dumb question.
If stars often form in collapsing hydrogen clouds when sufficient mass and thermal energy are accumulated, why is it beyond understanding to think stars may form in hydrogen clouds collapsing into SgrA's accretion disk?

-Veeger
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Old 26-April-2008, 11:33 PM
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Default Black Hole Creates Tidal Forces which Block Cloud Formation

In reply to Veeger's question.

Quote:
If stars often form in collapsing hydrogen clouds when sufficient mass and thermal energy are accumulated, why is it beyond understanding to think stars may form in hydrogen clouds collapsing into SgrA's accretion disk?
Hi Veeger,

The different clusters of young massive, short lived stars are located very close the Milky Way’s black hole. In that region of space, very, very close to a “black hole” the gravitational field from the massive "black hole" creates tidal forces which will pull apart a gas cloud. As noted in the attached quote, for a gas cloud to have sufficient internal gravitational forces to resist the black hole tidal forces, the density of the gas cloud would need to approach that of the density found in the outer atmospheres of stars which does not seem possible. I.e. A massive gas cloud would have needed to have collapse to form a super density gas cloud. The BH tidal force would have rip the gas cloud apart before it could have theoretically collapse. As noted in the comment, there are other known mechanisms that limit the size of a gas cloud that can collapse. (There is another problem/paradox in that the number of stars found concentrated in this region of space is very very high.) The mechanisms that limit how fast a gas cloud can collapse also limit the number of stars that can be formed in one area of space.

Comments:
1) There are other mechanisms (even if there was not a black hole in the immediate vicinity of the stars in question) that limit the size of the gas cloud that can collapses to such high densities. The collapse of the gas cloud is adiabatic, so the temperature of the gas must increase, which limits the maximum density of the collapsing cloud. (The gas can radiate which helps it cool, however the entire massive gas cloud cannot collapse, as the increase in temperature in one part of the gas cloud causes other of the cloud to expand.) Also when a star starts to form, the energy produced by stellar nuclear reactions heats the gas cloud causing it to expand and dissipate.

2)The stars in question do not form in the black hole accretion disc. The accretion discs' temperature is too high for stars to form in it.


http://arxiv.org/abs/0704.1281v1

The Galactic Center by R.Genzel and V. Karas

Quote:
If there is indeed a central black hole associated with Sgr A* the presence of so many young stars in its immediate vicinity constitutes a significant puzzle (Allen & Sanders 1986; Morris 1993; Alexander 2005). For gravitational collapse to occur in the presence of the tidal shear from the central mass, gas clouds have to be denser than ~10^9(R/(10′′))^−3 hydrogen atoms per cm^−3. This ‘Roche’ limit exceeds the density of any gas currently observed in the central region. Recent near-diffraction limited AO spectroscopy with both the Keck and VLT shows that almost all of the cusp stars brighter than K~16 mag appear to be normal, main sequence B stars (Ghez et al 2003; Eisenhauer et al 2005a). If these stars formed in situ, the required cloud densities approach the conditions in outer stellar atmospheres.
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Old 27-April-2008, 02:35 AM
neilzero neilzero is offline
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I have not seen the MM years abreviation before; does that mean 1,000,000 years? Are very young , massive, short lived stars more than 100 solar mass each? It does seem that a cloud of hydrogen of 10,000 solar mass or more, should be detectable by some means. Perhaps the last of these hydrogen clouds close to the galactic center became stars a few centuries ago? Neil
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Old 27-April-2008, 04:55 AM
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Default Paradox of Youth, Hypotheses

In reply to neilzero's comment:

Quote:
Are very young , massive, short lived stars more than 100 solar mass each? It does seem that a cloud of hydrogen of 10,000 solar mass or more, should be detectable by some means. Perhaps the last of these hydrogen clouds close to the galactic center became stars a few centuries ago? Neil
Hi Neil,

There appears to be agreement that a gas cloud of sufficient density could not have formed at that location. Also as noted below there appears to be agreement that the massive young stars could not have migrated to their current locations. (MM is a European abbreviation for a million. As noted below a star of 15M⊙ has a life of approx. 40 million years.)

The following is another excerpt from the galactic center review paper (see above for a link.)

Quote:
The young stars are also too short-lived and too light to have formed far from the Milky Way’s black hole, where the tidal field is weak, and then to have migrated in by dynamical friction. The “collection basin” for the migration of young MS stars of mass of M⋆ =15M⊙ and lifespan t⋆ =2×10^7 yr is only maxrdf ∼ 0.2pc, and for stars of mass M⋆ =3M⊙ and lifespan t⋆ =4×10^8 it is only maxrdf ∼0.5pc.
Quote:
The unavoidable conclusion is that if the young stars well inside the central parsec were formed locally, then they must have done so by a different mechanism than the collapse of self gravitating cold molecular gas clouds that occurs in normal star forming regions.
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Old 28-April-2008, 01:45 AM
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Quote:
Quote:
The unavoidable conclusion is that if the young stars well inside the central parsec were formed locally, then they must have done so by a different mechanism than the collapse of self gravitating cold molecular gas clouds that occurs in normal star forming regions.
Yes, and this happens in every Galaxy, and it happens right from the begging!

http://www.narrabri.atnf.csiro.au/pu...mages/ngc2915/

This IS first light...Stars being formed near the MBH of a Galaxy (this is NOT a Dwarf Galaxy!).

That "Core" accretion disc will grow more and more, looking like a larger and larger "Spheroidal Dwarf" (BCD)...Then the question becomes...Where are the "Quiet BCD's???...
Quote:
Indeed, so far, even in sheets, no secure candidate for quiet BCDs have been identified (Kunth & Östlin 2000, Legrand et al 2000).
http://www.usm.uni-muenchen.de/people/hopp/dw.html

AND, here is what a "Quite BCD" becomes/looks like...
http://www.nasa.gov/mission_pages/ga...ex-072505.html

When the "Arms" finally have enough star formation to be seen and are not 'hidden' by the brightness of the ever growing core.

This Star formation in the hot region of the core has NEVER even been accounted for in all of cosmology, and this is not only happening in the Milky Way, as William has linked to, BUT as I said, has been happening in the growth of ALL galaxies since they started as New galaxies, when their SMBH's were first Created, which is when and where the Quantum Gravity for String Theory can be "Tested"...Long GRB's from 2 sec's to 500 sec's!

Here is Andromeda doing the same thing.
http://hubblesite.org/newscenter/arc...05/26/image/a/

SO, all galaxies form their stars with a combination of 'Core Stellar Formation' AND, Dwarf Galaxy Cannabalism!!!
http://heasarc.gsfc.nasa.gov/docs/co...laxy_info.html
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Old 29-April-2008, 03:17 AM
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Default Blue Compact Dwarf Galaxies

Quote:
Quote:
The unavoidable conclusion is that if the young stars well inside the central parsec were formed locally, then they must have done so by a different mechanism than the collapse of self gravitating cold molecular gas clouds that occurs in normal star forming regions.
In reply to RussT's comment:

Yes, and this happens in every Galaxy, and it happens right from the beginning!
Hello RussT,

Thanks Russ. That is a interesting set of astronomical pictures. There should be some sort of relationship between a galaxy's massive compact object and the blue compact dwarf galaxies. I am going to look for more information.

http://www.narrabri.atnf.csiro.au/pu...mages/ngc2915/


Quote:
Much about blue compact dwarf (BCD) galaxies remains mysterious, such as how the neutral hydrogen obtained its shape, what drives current star formation, and why there is so much dark matter. NGC 2915 is located at the relatively nearby distance of 15 million light-years - just outside our Local Group of Galaxies.
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Old 02-May-2008, 03:05 PM
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Quote:
Originally Posted by William View Post
There appears to be agreement that a gas cloud of sufficient density could not have formed at that location. Also as noted below there appears to be agreement that the massive young stars could not have migrated to their current locations.
And yet they appear to be there. What's your point?
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Old 02-May-2008, 11:24 PM
matt.o matt.o is offline
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First of all, I think you need to be careful about mixing up your scales here RussT. The work quoted in the original post is on interesting young stars in the central parsec regions of our galaxy. The blue compact dwarf image you linked to shows star formation on the ~1000 parsec scale.

Quote:
Originally Posted by RussT View Post
Yes, and this happens in every Galaxy, and it happens right from the begging!

http://www.narrabri.atnf.csiro.au/pu...mages/ngc2915/

This IS first light...Stars being formed near the MBH of a Galaxy (this is NOT a Dwarf Galaxy!).
Are you sure NGC 2915 has a massive black hole? Are you sure this is the first star formation episode in this galaxy, and there isn't an underlying old stellar population? If so, can you link to papers which have studied this? I'd be interested in reading them.

Quote:
Originally Posted by RussT
That "Core" accretion disc will grow more and more, looking like a larger and larger "Spheroidal Dwarf" (BCD)...Then the question becomes...Where are the "Quiet BCD's???...
What exactly are you saying here? I am not sure whether you are saying the gas disk will grow in size, or the more star formation will happen in the core, thus increasing the bright optical core.

Quote:
Originally Posted by RussT
http://www.usm.uni-muenchen.de/people/hopp/dw.html

AND, here is what a "Quite BCD" becomes/looks like...
http://www.nasa.gov/mission_pages/ga...ex-072505.html

When the "Arms" finally have enough star formation to be seen and are not 'hidden' by the brightness of the ever growing core.
I am not sure this evolutionary sequence will occur. Notice in the image you show that the galaxies are interacting, implying the star formation is triggered by the interaction? If there is no trigger for the BCD gas to be turned into stars, why shouldn't the gas stay gas forever?

Quote:
Originally Posted by RussT
This Star formation in the hot region of the core has NEVER even been accounted for in all of cosmology, and this is not only happening in the Milky Way, as William has linked to, BUT as I said, has been happening in the growth of ALL galaxies since they started as New galaxies, when their SMBH's were first Created, which is when and where the Quantum Gravity for String Theory can be "Tested"...Long GRB's from 2 sec's to 500 sec's!
I am not sure what you mean in saying the star formation has never been accounted for. Can you explain? Also, do all galaxies have SMBHs? Not sure what you are referring to with the GRB, quantum gravity comments either? Can you elaborate?

Quote:
Originally Posted by RussT
Here is Andromeda doing the same thing.
http://hubblesite.org/newscenter/arc...05/26/image/a/

SO, all galaxies form their stars with a combination of 'Core Stellar Formation' AND, Dwarf Galaxy Cannabalism!!!
http://heasarc.gsfc.nasa.gov/docs/co...laxy_info.html
This may be true, but I'm not sure what your point is.
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Old 03-May-2008, 03:16 AM
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Default Working Hypothesis to Explain Observations

Quote:
In reply to Cougar's comment:
Quote:
Originally Posted by William View Post
There appears to be agreement that a gas cloud of sufficient density could not have formed at that location. Also as noted below there appears to be agreement that the massive young stars could not have migrated to their current locations.
And yet they appear to be there. What's your point?
I would propose a working hypothesis that the massive stars are created due to charge unbalance which fragments the MECO.

The Paradox of Youth stars occur in a region where gas clouds cannot theoretically form due to the tidal affects of the massive compact object. It is not physically possible for the stars in question to have migrated to the location, based on the short life times of the massive stars in the clusters and the maximum distance the stars could possible have moved in their lifetimes. There is no other working hypothesis.

Following the logic of the working hypothesis, if the stars in question were formed from MECO fragmentation, they do appear to be very similar to other stars except a significant higher percentage are very large stars. I am looking at observations and observation anomalies associated with galactic evolution, morphology, and mergers to see if I can find observational evidence and logic to support the working hypothesis.

Questions within the logic of the hypothesis, which I am looking for observations evidence to answer. Does the ejection of the charged MECO matter leave a neutral body? i.e. Is the process balanced, in terms of the release and timing of the release of negative and positive charge? The driving mechanism to create the charge unbalance is fast moving in falling plasma that is separated by the MECO's strong magnetic field such that positive ions move to one pole of the MECO and negative charge (electrons) to another. Assuming that the process occurs (i.e. Within the logic of the working hypothesis) there would be a charge unbalance on the surface of the MECO that would be released.

There has that paper that noted that quasar spectrum analysis shows evidence of an increasing long cyclic change in energy spectrum.


Comment:
I also provide a link to the two cusps (rings of stars) paper. The two rings of stars formed farther from the galactic core, 6 million years ago, all stars formed within a period of a million years. (In the region where the two ring of stars formed it is possible for gas clouds to form, however there are no gas clouds there currently.) The authors of the two cusps paper provide a hypothesis that the two rings of stars where created by colliding gas clouds but could not explain, and noted that they could explain, why the stars in question formed all at the same time (approx. 6 million years ago.) within a million years based on stellar analysis.
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Old 03-May-2008, 03:20 PM
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parejkoj parejkoj is offline
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Thank you for finally making a prediction, William. Now, can you provide the math that shows that a MECO can actually fragment, and show that the physical conditions that you assume in that model are physically viable? Please start a thread in the ATM section where you work this through, or cite a paper that does so.

Quote:
Originally Posted by William
The Paradox of Youth stars occur in a region where gas clouds cannot theoretically form due to the tidal affects of the massive compact object. It is not physically possible for the stars in question to have migrated to the location, based on the short life times of the massive stars in the clusters and the maximum distance the stars could possible have moved in their lifetimes. There is no other working hypothesis.
It's funny, how once again, the paper you linked in the OP has an explanation for your "impossibilities"

Quote:
Originally Posted by Alexander (2005), section 7
The solutions proposed so far for the riddle of the young stars (see reviews by Genzel et al. 2003b; Ghez et al. 2005) fall into three main categories: unusual modes of star formation near the MBH; rejuvenation of old stars from the local population; and dynamic migration or capture from farther out, where stars can form. While each has some attractive features, none is quite satisfactory. The paradox of youth remains unsolved at this time.
...
However, it is not clear that the required very high compression ratio (Eq. 7.1) can be achieved in such collisions.
...
This scenario has yet to be studied in detail. Here again, the problem is that it is unclear whether radiation pressure can lead to the very high compression ratio that is required for fragmentation.
...
The disk fragmentation model is a promising scenario for the formation of the star disks and the massive young stars on the 0.1 pc scale, but it is less clear whether it can account for the S-cluster as well.
...
The weakness of this scenario for explaining the S-stars is that, lacking quantitative calculations, it is unclear whether this method can actually form such a tightly bound cluster, and it is also unclear whether collisional stripping is efficient enough and consistent with the apparent normalcy of the B-stars.
That's a sample of the caveats for some of the "no other working hypothes[es]." Doesn't sound like any of them are "not physically possible," just that no one has yet studied this type of situation in enough detail. And, as is usually the case, the correct explanation likely involves the interplay of several of these models. I know some people who are working in this area: the problem is the number of effects that one must take into account in the models has only made them tractable (on large computing clusters) recently.

I'm waiting to see the quantitative predictions of your model of MECO fragmentation, including how the fragmentation products would look exactly like O and B stars and why they would have randomly oriented orbits.
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Old 03-May-2008, 04:02 PM
William William is offline
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Default Explanation for Observation

in reply to parejkoj's comment:

Quote:
Thank you for finally making a prediction, William. Now, can you provide the math that shows that a MECO can actually fragment, and show that the physical conditions that you assume in that model are physically viable? Please start a thread in the ATM section where you work this through, or cite a paper that does so.
As noted are no conventional explanations for the observation. There are multiple papers written about the observation.

And there is a second paper the discusses the second observation the two cusps of stars, which notes there is agreement that the paradox of youth stars cannot be explained by either in situ formation by gas cloud or by migration. (Migration is not possible based on the life time of the stars.)
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Old 03-May-2008, 04:26 PM
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I'll say this one more time:

Quote:
Originally Posted by me
Now, can you provide the math that shows that a MECO can actually fragment, and show that the physical conditions that you assume in that model are physically viable? Please start a thread in the ATM section where you work this through, or cite a paper that does so.
...
I'm waiting to see the quantitative predictions of your model of MECO fragmentation, including how the fragmentation products would look exactly like O and B stars and why they would have randomly oriented orbits.
Quote:
Originally Posted by William
As noted are no conventional explanations for the observation.
So, you are saying that the multitude of possible explanations in section 7.2 of Alexander are all irrelevant or incorrect?
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Old 03-May-2008, 07:47 PM
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Default Multiple Anomalies at Galactic Centre

in reply to parejkoj's comment:

Quote:
So, you are saying that the multitude of possible explanations in section 7.2 of Alexander are all irrelevant or incorrect?
I would say that in situ formation from a gas cloud or star migration does not address and does not attempt to address other fundamental questions connected with the observation. (For example, the authors who attempt to explain the simultaneous formation of two rings of stars that encircle the galactic core, specifically state that they do not have an explanation for why the formation of the two rings of stars, was near simultaneous.)

Paradox of Youth stars.
There are papers that specifically challenge in situ formation from a gas cloud or star migration as an explanation for the paradox of youth stars.

Two Rings of Stars Encircling Galactic Core
As the two rings of stars are further from the galactic core, it might be possible with a special very unusual external forcing event, for in situ formation from a gas cloud to explain the formation of two rings of stars that encircle the galactic core.

Hypothesis Logic
A hypothesis that must appeal to very special conditions to have occurred, the interaction of a satellite galaxy with the Milky Way, 6 million years ago, is a last resort hypothesis.

There are multiple problems with the gas cloud origin hypothesis to explain the galactic centre star clusters and rings of stars. Think of how stars are formed, the density of stars in the area, the number of massive stars in the area, and so forth...

1) The star clusters and the two rings of stars appear to have formed at the same time, for the group of stars in question. There is no explanation as to why a large group of stars would suddenly all form at the same time. The authors note they do have an explanation for the sudden formation of groups of stars.
2) There is a second problem of how to create a cluster of large stars in the same close area (30 stars in less than light year distance). The highly luminous stars will heat the gas cloud, stopping it from collapsing.
3) These problems are in addition to the problem of how to get a dense enough gas cloud in this area that will not be torn apart by the massive compact object.

The two rings of stars are at roughly the same distance from the massive compact object, have both formed roughly 6 million years ago and are at roughly 90 degrees to each other.

http://arxiv.org/abs/astro-ph/0601268v2

"The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation" by T. Paumard, Genzel, Martins, Nayakshin, Beloborodov, Levin, Trippe, Eisenhauer, Ott, Gillessen, Abuter, J. Cuadra, Alexander, Sternberg

Another explanation required than gas cloud origin required for "paradox of youth" stars
Quote:
The ‘paradox of youth’ in the central S-star cluster, with > 15 apparently normal main sequence B stars residing in tightly bound orbits in the central light month around the central black hole, probably requires yet another explanation (recently Ghez et al. 2003, 2005; Genzel et al. 2003; Hansen & Milosavljevic 2003; Gould & Quillen 2003; Alexander & Livio 2004; Eisenhauer et al. 2005; Alexander 2005; Davies & King 2005).
Two Rings of Stars
Quote:
Almost all of the ≃ 80 massive stars now known in the central parsec (central arcsecond galactic stars excluded) reside in one of two somewhat thick (h|h|/Ri ≃ 0.14) rotating disks.

Unusual Times Problem
Quote:
We do not have an explanation for the near simultaneous occurrence of two star formation events 6 Myr ago, followed by little since then, and preceded by little for tens of Myr (Blum et al. 2003). It is unavoidable to conclude that the epoch 4–9 Myr ago must have been a very special one for the Galactic Center. It is interesting and relevant to note in this context that the other two young, massive star clusters in the central 50 pc, the Arches and Quintuplet cluster, have comparable stellar masses (10^4Msolar mass), stellar content (WC/WN etc.), ages (2–7 Myr), and (flat) mass functions (Figer et al. 1999; Figer 2003; Stolte et al. 2005). We might speculate that star formation across the Galactic Center was triggered a few Myr ago by a global event, such as an interaction with a passing satellite galaxy that raised the pressure in the central interstellar medium and/or lead to increased cloud/cloud collisions.
Massive Stars, late sequence stars, Orbiting Massive Compact Object. Orbital distances as short as few light days?
Quote:
The lack of OB stars in these earlier studies is puzzling. The question is whether this lack is due to a true depletion or is merely a selection effect due to veiling of the weak absorption lines in near main sequence stars by bright nebular emission. Adaptive optics (AO) spectroscopy of the center-most arcsecond around Sgr A* (mostly devoid of nebular emission) has already revealed a dozen massive stars. These stars appear to be main sequence late O and B stars and orbit the central black mass at distances as short as a few light-days (Schödel et al. 2003; Ghez et al. 2003, 2005; Eisenhauer et al. 2005).
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Old 03-May-2008, 08:44 PM
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So you casually dismiss the formation mechanisms I've quoted from with a wave of your hand and expect us to take you seriously? While also ignoring my repeated calls for you to actually set forward your own model?

AND while once again quote-mining a paper!!! Paumard et al. titled section 4.1.1

"The In Situ Star Formation Scenario Is in Good Agreement with the Data"

I wonder why that is?

Can you please stop quote-mining papers?
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