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