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.


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.

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

In reply to Veeger's question.

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

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

In reply to neilzero's comment:

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.)

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???...
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

__________________
RussT
________________________________
Everything is, as it should be, otherwise, it wouldn't be!

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/

And yet they appear to be there. What's your point?

__________________
Everyone is entitled to his own opinion, but not his own facts.

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.

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.

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.

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?

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?

This may be true, but I'm not sure what your point is.

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.

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.

It's funny, how once again, the paper you linked in the OP has an explanation for your "impossibilities"

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.

__________________
"What do you care what other people think?" -- Richard Feynman
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." -- Feynman, at the conclusion of his Challenger report

in reply to parejkoj's comment:

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.)

I'll say this one more time:

So, you are saying that the multitude of possible explanations in section 7.2 of Alexander are all irrelevant or incorrect?

__________________
"What do you care what other people think?" -- Richard Feynman
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." -- Feynman, at the conclusion of his Challenger report

in reply to parejkoj's comment:

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
Two Rings of Stars

Unusual Times Problem
Massive Stars, late sequence stars, Orbiting Massive Compact Object. Orbital distances as short as few light days?

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?

__________________
"What do you care what other people think?" -- Richard Feynman
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." -- Feynman, at the conclusion of his Challenger report

parejkoj,

You are confusing the two rings of stars that encircle the galactic core which are farther from the galactic core with the s-stars which are referred to as the “paradox of youth stars”.

I agree, that in situ formation is possible for the two rings of stars, however as the authors of the ring paper note, a collision of two galactic gas clouds is required to explain the observation, which is possible, but unlikely. Requiring special condition weakens the hypothesis. As noted above there is no explanation as to why the stars all formed at the same time, which seems to invalidate the hypothesis, if the hypothesis is required to explain all observations. Perhaps you have an explanation, for the simultaneous formation paradox, which is a problem for each group of stars in the core area as they formed very, very, rapidly at specific intervals.

There are two rings, at 90 degrees to each other, formed at same time based on analysis of the star life. The the rings of stars rotate in the opposite direction.

There is as of yet no conventional explanation for the “paradox of youth stars”. Authors have also appealed to another gas cloud collision; however, tidal forces in that s-star area are two too high even with a gas cloud collision to create the necessary conditions for large star formation.

There is no explanation provided for the unusual number of large stars formed in both locations. But I guess if you really want to believe, the gap between observation and theory isn’t a problem.

Huh? How can two rings at 90^o rotate other than perpendicular to each other?

__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

In reply to Kaptain K's

The star disks are orientated to each other and to the galactic plane more or less than 90 degrees. I believe the authors are comparing the disk of stars rotation to the galactic rotation, to determine a reference. (i.e. If your reference starts looking down at the galaxy and then move in one direction, looking down at the first and then second disc.)

The following is from the paper:

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

No, you are simply ignoring what was written in those papers, some of which I've quoted above. Alexander (2005) listed multiple possible explanations for the formation of the stars that are now orbiting SgrA*. That's what the various "unclear" and "lacking quantitative detail" bits were referring to in the quote that I gave above, and that you oh-so-conveniently ignored. None of them are individually satisfactory yet, but that doesn't mean that they are all wrong.

And did you just neglect to read section 4.1.1 of Paumard?

And, once again:

I'm going to keep quoting myself until you cease ignoring me.

__________________
"What do you care what other people think?" -- Richard Feynman
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." -- Feynman, at the conclusion of his Challenger report

I knew I was going to regret jumping into this [mess]! I'll go back to just watching.

parejkoj, you have far more patience than I!

__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

I should not have really responded to this thread because I do not even think that the ECO/MECO/Gravistar paradigm is correct, so now we would just be having noisy dual conversation midst William's and parejkoj's.

But, I will address your questions and observations one time.

I was addressing more the "Young Star" formation in the "Hot" accretion/central core area arena. I am not sure of the parsec's scale of the diameter of the "Bright Core" of the Ghost Galaxy.

[Are you sure NGC 2915 has a massive black hole?]

matt...Please link again to the Ghost Galaxy 2915, and please take at least several minutes to study it as a "Full Fledged" but "Young spiral galaxy"

Now, with all of the 'Inferences" that mainstream makes, I do not think that making the inference, based on everything we know about spiral galaxies, that there IS a SMBH at the center of this "Obvious" HI cloud of spiral structure. You can even see where the "Bar" is going to eventually be in ??? 10 million/50 million/100 million/longer? years.

And, since you asked about first star formation...what would this galaxy be "Before" that little core "Lit Up"???

[Are you sure this is the first star formation episode in this galaxy]
Yes, I am! And here is a very thorough paper on that...there are others!
The Link no longer works...The paper was at GK Workshop and the author was T.X. Thuan.

[and there isn't an underlying old stellar population? ]

It is my very firm Opinion that the "Tip of The Red Giant" (TRG) population of 1 to 10Gy stars is totally contrived to 'try' to invalidate "Young Galaxies" from even existing!!! There have been recent findings that there is a whole population of very large/massive and therefore short lived Red Stars...I don't remember where I saw that.

I see. NO, the gas is already there, in the core and the disc, But more and more star formation will occur in the core to make it brighter and larger...The Bar still has to form....right? The core build up keeps getting bigger and bigger...just look at how many galaxies have much smaller cores than M31, BUT, there is a stage, where what is considered a BCD, finally shows it's 'arms'...making it an LSB, when the disc stars finally get bright enough to NOT be outshown by the bright core.

The clues are all there, if they are looked at correctly.

[If there is no trigger for the BCD gas to be turned into stars, why shouldn't the gas stay gas forever]

http://adsabs.harvard.edu/cgi-bin/np...3fc2ad35027763

I meant star formation in the 'Hot Zone'.

Yes, and dwarf galaxies as well. How else would they be 'rotating' like a galaxy? If it looks like a "Duck"!!! You will see what I am saying in my next response.

The short answer is this...

I am well aware that there are many paradigms of SMBH formation and it is my firm opinion that the ECO/MECO and even Joe Silks Group et al;...the collapsing cloud hypothesis, are all way off track, and all because it has always been assumed that "ALL" of the Gas...Hydrogen/Helium/Lythium/Deuterium must have already been there...BUT, it is my firm opinon also, after much research and investigation and true understanding, that the Microwave background energy is in the form of an ocean of Neutrinos that carry that background energy and that those Neutrinos are the Strings of String/"M" theory, making them background independent, and when those Strings form Branes and Collide in "Empty Space", that that gravitational Collapse triggers a major Gamma radiation Event, and creates the electrons/protons for that SMBH's galaxy. Galaxies have been forming that way for 10's of billions of years and 'falling' into their respective clusters.

__________________
RussT
________________________________
Everything is, as it should be, otherwise, it wouldn't be!

It looks like NGC 2915 has never experienced any significant mergers (how else would it hold onto that neutral hydrogen envelope?), so it likely doesn't possess a central massive black hole. I wasn't able to find any papers constraining it one way or the other, but the fact that its is relatively undisturbed and very low mass suggest that it any central black hole is not very high mass (a thousand solar masses at most).

Actually, small galaxies likely do not have a SMBH. The central black hole is not required to make the galaxy rotate (where did you get that idea?), nor will they grow significantly if the galaxy has not experienced any significant mergers. The merger history is generally evidenced by the presence of a large bulge. In galaxies without a bulge, such as M33 and many dwarf galaxies, there may be no central black hole present larger than a few thousand solar masses.

Do you actually have a workable hypothesis for this that you could defend in the ATM section? I'm especially interested in your suggestion that the CMB is carried by neutrinos, and how you intend to make that mesh with our observations of both the neutrino background and the properties of the CMB.

Kaptain K:
Incase you weren't able to figure out William's answer, the two clusters are roughly perpendicular. Figures 4 and 5 in the paper should help you visualize it.

__________________
"What do you care what other people think?" -- Richard Feynman
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." -- Feynman, at the conclusion of his Challenger report

Galaxy M33

Galaxy M33 may have a very small black hole at the M33 Galactic core. It does seem to have some action at the core. This ROSAT image states that M33 has 180 discrete x-ray sources near its core. M33 like the Milky Way also has star bursts in its core region.

Following the gas cloud hypothesis there must therefore from time to time be new large gas clouds that are pulled into the core.


http://wave.xray.mpe.mpg.de/rosat/calendar/2002/feb


http://arxiv.org/PS_cache/astro-ph/p.../0305584v1.pdf

IF, the Ghost Galaxy 2915 were seen "edge on"...then it would be even more dramatic than this!!!

http://www.sciencedaily.com/releases...0411070039.htm

And also...

http://www.space.com/scienceastronom...lack_hole.html

__________________
RussT
________________________________
Everything is, as it should be, otherwise, it wouldn't be!

The following is additional information concerning the Milky Way’s Paradox of Youth stars, which are referred to in papers collectively as “S2”. They have an orbit of 2 light days about the Milky Way’s massive compact object.

From “An Introduction to Modern Astrophysics” by Carrol & Ostlie 2nd Ed. published 2007, Page 924, Chapter 24, Milky Way Galaxy.

What is the source of hostility Parejkog displays towards William? Bill, do you owe Mr. Kog money or date his ex or something?

As an outsider just wandering into this thread it looks like Parejkog is being mean to William for no good reason.

Yep, I just looked, we are in the Astronomy section, not the ATM section. I ask questions here I don't have the answers to here all the time, because if I had the answers, I wouldn't have the questions!

__________________
In your rush to call everyone "entrenched" or closed-minded or "limited" you fail to note that the "limit" here has a very natural boundary: that point at which the evidence stops. - JayUtah

Science fiction was never meant to be an educational tool. - Editor Amazing Tales

Because William has carried ATM over into the Astronomy Forum, is cherry picking and causing Parejkoj a bit of frustration.

Okay, fair enough Nev.

But wouldn't it be fair to say that if William thought enough of this subject to post an ATM thread, it would be something that preys on his mind a lot? For all we know he has that Asberger's Syndrome or something.

Maybe he just wants to talk about it outside of the cage match/shark tank that is the ATM section. You may not know it, but shadow boxing is very important in preperation for the ring.

And as far as answering Paregkog's questions, how does rules concerning the prompt answering of questions jibe with the right to have an "ignore" list? The two don't quite mesh well in my opinion.

William, sorry for the highjack.

Paregkog, apologies for the seemingly hostile replies on *my* part.

__________________
In your rush to call everyone "entrenched" or closed-minded or "limited" you fail to note that the "limit" here has a very natural boundary: that point at which the evidence stops. - JayUtah

Science fiction was never meant to be an educational tool. - Editor Amazing Tales

BigDon: not a problem. I was not trying to be snarky, just trying to make sure I was heard.

William has repeatedly started threads in both Q&A and Astronomy where he has "questioned" the mainstream by quote-mining papers and ignoring when those very papers contradict his own statements. And then ignoring or brushing me off when I point it out to him (this thread is a perfect example). By his own statements, he has shown a significant misunderstanding of the very papers he quotes, while often responding to criticism by suggesting that we read some basic text which he himself misunderstands.

He also repeatedly hinted at an ATM idea but has never started a thread in the ATM section to defend that idea. I've asked him to do so on a few occasions in the past, and again been ignored or given a promise that he will not bring it up again. And then a few weeks later, another few threads appear where he dances around again...

The topics that he starts threads on are generally interesting, and occasionally active areas of current research, such as this one. I (and others) don't have time (or always expertise) to go and correct every misconception he posts about some cutting edge area of astrophysics. What we need is a JayUtah of quasars. I'm not there yet...

oh: and it's parejkoj!

__________________
"What do you care what other people think?" -- Richard Feynman
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." -- Feynman, at the conclusion of his Challenger report

Well thank you for your reasonable reply parejkoj. I shall remain quiet at this point.

__________________
In your rush to call everyone "entrenched" or closed-minded or "limited" you fail to note that the "limit" here has a very natural boundary: that point at which the evidence stops. - JayUtah

Science fiction was never meant to be an educational tool. - Editor Amazing Tales