UK astronomers spot biggest star ever

[Steffen]

Just saw this on ABC News - what a whopper!

Cheers
Steffen.

[renormalised (Carl)]

Thought we might see a monster in that particular cluster. It's the central region (R136) of the cluster that sits in the Tarantula. There's quite a few more monster stars in there apart from that one. It wouldn't surprise me if there's an even bigger one sitting in there somewhere. Something like 20000 solar masses lies within the central light year or so of the cluster. It's one of the densest star cluster around....rivals the Arches and Quintuplet Clusters for density.

[glenc (Glen)]

There is some more about R136a1 here: http://www.physorg.com/news198924098.html
NGC 3603 also has big stars.

[Jarvamundo (Alex)]

Originally Posted by glenc

There is some more about R136a1 here: http://www.physorg.com/news198924098.html
NGC 3603 also has big stars.

Interesting comments...
"no word on the stars diameter or its density..."

I have some questions:

The existence of these monsters -- millions of times more luminous than the sun, losing weight through very powerful winds

1) Weight loss: So have you detected "weight loss" or is this an assumption from the model?

Using a combination of instruments on ESO's Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the sun, or twice as much as the currently accepted limit of 150 solar masses.

2) You say, this is beyond the "accepted limit" so it is clearly outside of "the models" range of assumptions. Are these the same assumptions you are using to infer the "weight"?

Comparisons with models imply that several of these stars were born with masses in excess of 150 solar masses.

3) Which models? i thought 150 solar masses was the limit? Is this another way of saying "nfi"?

"Unlike humans, these stars are born heavy and lose weight as they age," says Paul Crowther. "Being a little over a million years old, the most extreme star R136a1 is already 'middle-aged' and has undergone an intense weight loss programme, shedding a fifth of its initial mass over that time, or more than fifty solar masses."

4) ok... i'll give you that one... that star is not a human.... but... Which model are you using to determine if this star is middle aged? If you have no model that fits, are you not just making speculations beyond any accepted physics?

I find the article contradictory all the way through....

Empirics:
a) it's bright... real bright...and contains spectrum of heavy elements?
b) no determination of dimensions provided in article(s)
c) can't see any mention of orbital dynamics?

Is all this just "inferred" from spectrometry and flux counts?

I suspect, you have only inferred from a broken model that you say yourself does not permit these measurements?

Very confusing!

edit: link to paper... yes inferred mass it's all from flux counts and estimates from models that as they mention, clearly don't stand up... Why not just say that?
I'm finding it really hard to swallow the "coalescing gas" model of star formation, when with all this "wind" around... and this supermassive "young" short-term stars... anyone slightly familiar with thermodynamics knows hot "wind" gas aint guna hang around long enough to form stars... totally counter intuitive.

[renormalised (Carl)]

Originally Posted by Jarvamundo

Interesting comments...
"no word on the stars diameter or its density..."

I have some questions:

1) Weight loss: So have you detected "weight loss" or is this an assumption from the model?

2) You say, this is beyond the "accepted limit" so it is clearly outside of "the models" range of assumptions. Are these the same assumptions you are using to infer the "weight"?

3) Which models? i thought 150 solar masses was the limit? Is this another way of saying "nfi"?

4) ok... i'll give you that one... that star is not a human.... but... Which model are you using to determine if this star is middle aged? If you have no model that fits, are you not just making speculations beyond any accepted physics?

I find the article contradictory all the way through....

Empirics:
a) it's bright... real bright...and contains spectrum of heavy elements?
b) no determination of dimensions provided in article(s)
c) can't see any mention of orbital dynamics?

Is all this just "inferred" from spectrometry and flux counts?

I suspect, you have only inferred from a broken model that you say yourself does not permit these measurements?

Very confusing!

edit: link to paper... yes inferred mass it's all from flux counts and estimates from models that as they mention, clearly don't stand up... Why not just say that?
I'm finding it really hard to swallow the "coalescing gas" model of star formation, when with all this "wind" around... and this supermassive "young" short-term stars... anyone slightly familiar with thermodynamics knows hot "wind" gas aint guna hang around long enough to form stars... totally counter intuitive.

My advice Alex is to grab a textbook book on star formation and the physics behind it. Or goto arXiv.org and grab some of the papers on the subject, especially about the formation of massive stars. You'll learn a bit about the subject by doing so. But, grab the textbook first...get the basics then go onto the harder stuff later.


That wind they're talking about isn't what you think. It's the continuum wind that blows all the time around these stars. It's like an "uber" solar wind, except the driving mechanism is somewhat different.

The 150 solar mass limit is due to the Eddington Limit imposed upon such large stars, however it's not fully understood and is open to change, as you have seen here. The precise cutoff in mass due to the Eddington Limit is a fluid thing and is affected by quite a few factors, least of which is how hot the star is.

The only way to determine the star's size is via spectroscopic analysis. Even in a wide binary, you still need a spectroscope to determine the orbital velocity of the star, apart from other characteristics. And at the distance this star is at, you're not going to be able to directly measure it's angular diameter....it's just too far away. So, you can determine it's size from stellar theory and what measurements you can and do take.

[ManOnTheMoon (Matt)]

Just because a human says the biggest a star can get is around 150 solar masses doesnt make it correct. These things are always changing and being updated as we discover more. How do we know a limmit on star size even exists? The universe it way to big and vast for us to comprehend and we proberly only understand a very small part of what make's it tick. We can look right back to images from just after the big bang but we are looking backwards into the very distant past the further out into space we look. We cant see what the very distant universe really looks like right at this instant not for another 10+ billion years anyways.

[Jarvamundo (Alex)]

The theoretical limit at which the radiation pressure of a light-emitting body would exceed the body's gravitational attraction. A star emitting radiation at greater than the Eddington limit would break up. This would happen, for example, to a star of more than about 120 solar masses, or to the Sun if its luminosity were increased by a factor of 30,000. The Eddington limit, named after Arthur Eddington, is given by

ok... so we now have a star WAY WAY WAY beyond this limit...

what would be the point of 'grabbing a text book'?

This particular fusion model (found in books) HAS BEEN FALSIFIED by this article!

That wind they're talking about isn't what you think. It's the continuum wind that blows all the time around these stars. It's like an "uber" solar wind, except the driving mechanism is somewhat different.

Sure... how are 2 hydrogen atoms in this "wind" seriously going to contemplate paying attention to their pathetic gravity to form a star.

Sorry whatever type of wind it is (and all we have to compare is a solar plasma sheath driven by charged particles from the star)... it's counter intuitive to *some* coalescing gravity gas models (and yes many have now moved away from endorsing these models).

Originally Posted by renormalised

The only way to determine the star's size is via spectroscopic analysis. Even in a wide binary, you still need a spectroscope to determine the orbital velocity of the star, apart from other characteristics. And at the distance this star is at, you're not going to be able to directly measure it's angular diameter....it's just too far away. So, you can determine it's size from stellar theory and what measurements you can and do take.

Thanks Carl, pretty much sums up my concerns of what they say "IS".

Yes! I agree, It's totally fluid, although it is clearly not presented this way in articles. Instead of focusing on their empirical measurements, they have invoked theories which THEY STATE are violated, then drum a story.

Just because a human says the biggest a star can get is around 150 solar masses doesnt make it correct.

Sorry no, models will need to have an empirical basis with known physics... otherwise it's just wild liquid conjecture. Yes it's a part of science, but it's weak science to rely on.

How do we know a limmit on star size even exists?

Lets be very clear, these masses are Man's inference of star mass... as they say it violates current accepted limits.

maybe i'm expecting to much from these press releases...

"MOST MASSIVIST STAR" ohh wow.... move along.

[renormalised (Carl)]

Originally Posted by Jarvamundo

ok... so we now have a star WAY WAY WAY beyond this limit...

what would be the point of 'grabbing a text book'?

This particular fusion model (found in books) HAS BEEN FALSIFIED by this article!

Sure... how are 2 hydrogen atoms in this "wind" seriously going to contemplate paying attention to their pathetic gravity to form a star.

Sorry whatever type of wind it is (and all we have to compare is a solar plasma sheath driven by charged particles from the star)... it's counter intuitive to *some* coalescing gravity gas models (and yes many have now moved away from endorsing these models).



Thanks Carl, pretty much sums up my concerns of what they say "IS".

Yes! I agree, It's totally fluid, although it is clearly not presented this way in articles. Instead of focusing on their empirical measurements, they have invoked theories which THEY STATE are violated, then drum a story.

Sorry no, models will need to have an empirical basis with known physics... otherwise it's just wild liquid conjecture. Yes it's a part of science, but it's weak science to rely on.

Lets be very clear, these masses are Man's inference of star mass... as they say it violates current accepted limits.

maybe i'm expecting to much from these press releases...

"MOST MASSIVIST STAR" ohh wow.... move along.

If you grab that textbook, no matter that we have an approximate handle on the evolution of very massive stars, you will still learn the basics of how stars form and the physics behind it. Without that basis, trying to understand anything else is a moot point. You won't be able to, simple as that.

The particular fusion model found in books has not been falsified at all. This has very little to do with fusion. It has everything to do with mass, composition, metallicity, and radiative energy dynamics. Fusion only provides the energy and that is a core region phenomenon. It provides the energy which drives these other processes, but what happens in the core is pretty well known.

You still don't get it....this wind is a consequence of the mature star, not the protostar which formed from the gas/dust cloud initially. These stars in the article are not protostars/pre-main sequence stars. The physics of their formation is separate from their present state.

They have focused on their empirical measurements and applied those measurements to theory, otherwise how could they come to the conclusions that they have??!!. It's the only way they could've wrote what they did....the only way any scientific paper is written, unless you set out to talk theory exclusively, in the first place. In which case, it's then a purely theoretical paper, which this one isn't.

The problem here is you have made assumptions about the theory and the empirical data within the article which cannot be supported by the science which is actually there. You need to learn about the theory first, before you can make comment on what the article presents, otherwise when you make comment, you're in a position of not knowing enough to understand what's been written, so any comment you therefore make is not informed. Regardless of what you may know about any other subject.

Anyone with half a brain and a reasonable knowledge of science could find fault in any journal article, if they so choose. Science is not about being 100% watertight in theory or even in empirical measurement of the phenomena we observe. It's about using the tools and the theory we do have to try and explain the things we observe, knowing that it maybe wrong to begin with, but also knowing that the more we do look, the chances being we're going to be right at some stage. I think our knowledge of stellar evolution and physics, whilst not 100% correct, is fairly solid. Otherwise, what would be the point of trying to understand any of it to begin with.

What do you propose is the mechanism for the formation of stars, especially these very massive ones, if you believe that present theory is inadequate or even incorrect in it's assumptions about what is happening??

However, remember, these are fully formed stars...not pre-main sequence or protostars, so you will have to separate the physics of the pre ZAMS star from their current condition.

[Jarvamundo (Alex)]

Being a little over a million years old, the most extreme star R136a1 is already 'middle-aged' and has undergone an intense weight loss programme, shedding a fifth of its initial mass over that time, or more than fifty solar masses."

NGC 3603 is a cosmic factory where stars form frantically from the nebula's extended clouds of gas and dust

So this star is a little over a million years old... in an area where "stars form frantically".

Carl, are you sayin proto stars and pre-main sequence stars already exist in this region?... it is just the last stage of development that is called "forming".

Sorry, i was a little ambiguous in my previous post, i was commenting on the ability of the "frantic gas" in the region to remotely pay attention gravity, thus frantically "form".

[renormalised (Carl)]

Stars are forming in the region all the time. Some of the stars are fully formed, others are still in the process of forming. Some of those stars are in the early to middle stages of formation and are protostars, others are more advanced in those stages and are pre-main sequence stars. Some haven't even started to form, yet, and are still globs of dust and gas (Bok Globules, etc).

Those big stars don't take long to form at all. Most only stay in the pre-main sequence stage of development for 50000-100000 years. Protostar stage can draw out a bit longer, but they take far less time to form than a solar mass star. Takes a solar mass star about 20-30 million years to form, most of that in the pre-main sequence stages.

[Jarvamundo (Alex)]

Yeah, this is where i'm having difficulties swallowing the hypothesis of gas coalescing under gravity in that active environment.

Anyways, thanks for your input.

[renormalised (Carl)]

Originally Posted by Jarvamundo

Yeah, this is where i'm having difficulties swallowing the hypothesis of gas coalescing under gravity in that active environment.

Anyways, thanks for your input.

Actually, it's more likely to coalesce in that environment than it otherwise would because of all the interactions that are going on. The high energy radiation in those areas tends to form shock waves and turbulence which causes Bok globules and such to contract when they run into them. However, that ionising radiation can also destroy them as well, so it's a matter of balance and good luck (plus, just how dense the globules are and how big they are, etc). Once the clouds exceed their Jeans Masses, gravity can do a very good job of holding onto the material to form the stars. However, to form those really big stars, they have to be in high energy, dense environments because once stars start to form, it's easy to form smaller stars than larger ones. The clouds tend to fragment into smaller protostars because of the internal dynamics of the globules and to form the larger stars, the surrounding conditions have to balance out those internal dynamics. Usually, clouds of relatively high metallicity form smaller stars as their Jeans Masses are relatively low before they begin collapse.

Those monsters in R136 probably formed out of protostellar clouds with Jeans Masses up around the 5000-10000 solar masses before the clouds began to contract and fragment into protostars. The low metallicity means the clouds were far more transparent to radiation than a typical cloud in the Galaxy and their cores were less dense when collapse begins. Because of the properties of the gases they formed out of, the protostars in these large clouds stay relatively large and the clouds don't fragment as much. Hence, larger stars.

[ngcles]

Hi Steffen, Alex, Carl & All,

Thanks for taking the time to alert us all to that finding Steffen.

Alex, with respect, it seems to me that you are approaching this story from the point of view that if something a little surprising is observed then that means the baby has to go out with the bath-water -- which isn't so. In fact this particular finding (observation) is not completely surprising based on the way the models and observations have been moving over the last 10-20 years.

Maybe you are expecting too much from these press releases? Correct -- remember they are designed for journalists who may occasionally have a little scientific literacy but more often than not (particularly in the popular press) have none at all.

The Hayashi and Eddington "limits" (please note the quotation marks carefully) as part of stellar theory were things proposed some time ago. Our (ie Astronomer's) knowledge, technology in detectors (and includes our ability to make predictive models on super-computers) and observational capability have increased quite a bit since then. They have until quite recently been somewhat rubbery on this issue and findings like this are helping to solidify them just a little more. No one has been pretending that either they’ve not been rubbery or that they are graven in stone.

The idea that there is a limit as to how massive a star can possibly be has been around for quite a while but not all the factors that affect how long that piece of string is going to be (in a particular case) were not well known back then (in the times of Eddington etc), are better appreciated now (though far from completely) and in time to come will be known with better certainty still. Not for a moment has any reputable astronomer or physicist on this question nailed his colours to the mast and said "They can be this big and no bigger, never-ever-ever -- Amen" As Carl has already pointed out, it is now appreciated that rotation (and/or the lack of it), temperature and metallicity will have a dramatic effect on how big, in theory, (and practice) a star can be without its own radiation pressure blowing it to pieces. Exactly how much effect is still being worked out. On this particular issue, nobody is pretending we were (or are) home and dried. In fact no one is pretending we’re even home and vigorously towelling off.

One of the biggest problems facing astronomers in defining this limit is both the extreme rarity and extremely short lives of these ultra-super-dooper high-mass stars. Have we seen that absolute limit yet? I don’t think anyone is pretending we have. It may be higher again. Then maybe it will not be higher and "this is it". Maybe the ones at the very apex of the tree are so incredibly rare that the sum total in the local Universe at the present moment in time is nil?

Does this finding mean we have to throw out all our current stellar theory? No.

In fact it is believed that even more massive stars than these lived in the very earliest epoch of the Universe – the Population III stars that may well have ranged up to 500 solar-masses or even beyond. How could this be? The short answer probably hinges on the question of metals (or more precisely their complete absence in the so-called Population III stars). Have we found these Population III stars yet? Not with certainty, but there is now some evidence of them. Time will tell.

And Alex, are you willing to take up Carl’s earlier invitation: “What do you propose is the mechanism for the formation of stars, especially these very massive ones, if you believe that present theory is inadequate or even incorrect in it's assumptions about what is happening??


Best,

Les D

"Quote me as saying I was mis-quoted." -- Groucho Marx

[Jarvamundo (Alex)]

Originally Posted by renormalised

Actually, it's more likely to coalesce in that environment than it otherwise would because of all the interactions that are going on. The high energy radiation in those areas tends to form shock waves and turbulence which causes Bok globules and such to contract when they run into them. However, that ionising radiation can also destroy them as well, so it's a matter of balance and good luck (plus, just how dense the globules are and how big they are, etc). Once the clouds exceed their Jeans Masses, gravity can do a very good job of holding onto the material to form the stars. However, to form those really big stars, they have to be in high energy, dense environments because once stars start to form, it's easy to form smaller stars than larger ones. The clouds tend to fragment into smaller protostars because of the internal dynamics of the globules and to form the larger stars, the surrounding conditions have to balance out those internal dynamics. Usually, clouds of relatively high metallicity form smaller stars as their Jeans Masses are relatively low before they begin collapse.

Those monsters in R136 probably formed out of protostellar clouds with Jeans Masses up around the 5000-10000 solar masses before the clouds began to contract and fragment into protostars. The low metallicity means the clouds were far more transparent to radiation than a typical cloud in the Galaxy and their cores were less dense when collapse begins. Because of the properties of the gases they formed out of, the protostars in these large clouds stay relatively large and the clouds don't fragment as much. Hence, larger stars.

Carl what is the role of charge separation here?

As we know the Solar Wind accelerates as result of charge separation.... you talk of "pressure waves"?, i'm just wondering now we have high collisions and lots of "ionising radiation".... so charge separation has developed.... and a circuit will build... thus forming the Birkeland filaments and current sheets...

How does this charge separation feature in the model, id be interested to see how this is (or is not) currently incorporated in mainstream models?

Originally Posted by Lez

Alex, with respect, it seems to me that you are approaching this story from the point of view that if something a little surprising is observed then that means the baby has to go out with the bath-water -- which isn't so. In fact this particular finding (observation) is not completely surprising based on the way the models and observations have been moving over the last 10-20 years.

I guess i might just be hoping for some solid predictions to come from these models Lez, rather than the patch it up and move along.

If your limit is X... then it's now been popped to 2X.... whats next 10X? All good... but it seems to fluid to pay attention to.

Originally Posted by Lez

And Alex, are you willing to take up Carl’s earlier invitation: “What do you propose is the mechanism for the formation of stars, especially these very massive ones, if you believe that present theory is inadequate or even incorrect in it's assumptions about what is happening??

I'm not sure if this is trollish...

I see no need to have an alternate theory if your current one is not making predictions that match measurements. I guess it may depend if one can sleep without a feel good saftey blanket.

I have explored Hanne's Alfven's, Ralph Jeurgen's, Wallace Thornhill's, Dr Don Scotts, models of electric stars, which actually make predictions of both this variety and also variability, and have the advantage of lab physics empiricism.

http://www.electric-cosmos.org/sun.htm
http://www.holoscience.com/news.php?article=74fgmwne

Particularly interesting in this case is the variability predictions of the models:
http://www.electric-cosmos.org/hrdiagr.htm

Mainstream astronomy attempts to describe how stars 'age' (run out of nuclear fuel) and slowly migrate, taking hundreds of thousands of years to do so, tracing paths from one location on the HR diagram to another (the star going from one spectral class to another). The paths that stars 'must take' are, of course, completely predicated on the assumption that stars are fueled by the various stages of nuclear fusion of the lightest elements.

The ES model does not make that assumption. Humans have not been around long enough to actually observe any stars making the predicted slow migrations from one place on the HR diagram to another. So, at present, slow "stellar evolution" is another one of those complicated theoretical constructs that live brightly in the minds of astrophysicists without any observational evidence of their actual existence.

Both models, the standard and the electric make some distinctly different predictions with regard to stellar evolution.

I see these differences as being testable.

NASA now has now involved Don Scott, in exploring these hypothesis.
http://www.youtube.com/watch?v=wOI-X215A8Y