Is 13 Billion Years Enough for Carbon Abundance in the Universe?

[TrickyDicky]

There's this kid mentioned in another thread that seems to raise doubts about carbon nucleosynthesis but the thread was locked, so I thought I'd ask the experts :If all the carbon of the universe is produced in masive stellar fusion nucleosynthesis, is 13 billion years time enough to reach the present high abundance of this element in solar systems?

 

[Vanadium 50]

Yes.

 

[phyzguy]

I agree with Vanadium. Clearly yes. Carbon currently represents about 0.4% by weight of the ordinary matter in our galaxy, so the abundance is really not that high. You're seeing a skewed abundance in a place like the Earth, because on a terrestrial planet the main elements (hydrogen and helium) evaporate away.

 

[TrickyDicky]

I agree with Vanadium. Clearly yes. Carbon currently represents about 0.4% by weight of the ordinary matter in our galaxy, so the abundance is really not that high. You're seeing a skewed abundance in a place like the Earth, because on a terrestrial planet the main elements (hydrogen and helium) evaporate away.

I thought apart from H and He of course, Carbon was the second abundant element in the universe, pretty close to Oxygen.

But I have seen a couple of references in the first page after I googled "carbon nucleosynthesis" that point to a carbon open issue for instance with the origin of high carbon abundances in the early universe, as in this article's named "The origin of carbon: Low-mass stars and an evolving, initially top-heavy IMF?" by L. Mattson abstract where they conclude: "The stellar origin of carbon remains an open question, although production in low- and intermediate-mass stars appears to be the simplest explanation of observed carbon abundance trends"
Actually I thought models of stellar nucleosynthesis say that in low mass stars carbon is kept in the core and it doesn't spread out.
Anybody?, any hint about this?

Though I must say that after the extense and highly educational answer by Vanadium 50 in post #2 I wonder what else can be said.

 

[phyzguy]

My numbers have current abundances with H at 71%, He at 27%, O at 1%, C at about 0.4%, and Fe and Ne next at about 0.2% each (all by weight). How detailed a model are you looking for? There clearly has been enough time to produce this much carbon, given the large uncertainties in things like how much stellar mass get recycled into the ISM, and the exact distribution of elements produced during different types of supernovae. But I think these questions have to do more with adding detail to the current model of stellar nucleosynthesis, rather than calling stellar nucleosynthesis itself into question.

 

[Chronos]

Obviously low mass stars, like the sun, are not major contributors to the interstellar carbon inventory, but, type II supernova are prime suspects. Progenitor stars' atmospheres are carbon rich and, when the core collapses, most of this carbon is dispersed into space.

 

[Ken G]

But I have seen a couple of references in the first page after I googled "carbon nucleosynthesis" that point to a carbon open issue for instance with the origin of high carbon abundances in the early universe, as in this article's named "The origin of carbon: Low-mass stars and an evolving, initially top-heavy IMF?" by L. Mattson abstract where they conclude: "The stellar origin of carbon remains an open question, although production in low- and intermediate-mass stars appears to be the simplest explanation of observed carbon abundance trends"
Actually I thought models of stellar nucleosynthesis say that in low mass stars carbon is kept in the core and it doesn't spread out.

I think that's just what they meant by the "open question" in the stellar origin of carbon-- not that it's open as to whether stars do it (there's no other game in town), but rather, whether high-mass or low-mass stars do it. It was long thought that low-mass stars retained their carbon, so were not an important source for the ISM, but this is just what recent studies have called into question. I don't know the details about it, but my impression is, the dense winds of AGB stars (low-mass stars becoming red giants for the final time) are now thought to be important carbon sources for the ISM. Judging from the title of that paper, I might speculate that what they are talking about is a process where high-mass stars in the initially "top-heavy" IMF would dominate early carbon formation, but this tends to change the IMF until more low-mass stars are made, which then take over as carbon sources to the IMF.

 

[TrickyDicky]

I think that's just what they meant by the "open question" in the stellar origin of carbon-- not that it's open as to whether stars do it (there's no other game in town), but rather, whether high-mass or low-mass stars do it. It was long thought that low-mass stars retained their carbon, so were not an important source for the ISM, but this is just what recent studies have called into question.

So would say that without those alternative sources of carbon based on alternative stellar evoulution trends, the high mass only stars could account for the observed carbon abundance in the 13 bly time span considered?

 

[Ken G]

I don't know myself, but the conclusions that others seem to be reaching is that yes, the high-mass stars by themselves could not have produced the ISM carbon in 13 billion years, they need some help from low-mass stars.

 

[TrickyDicky]

I don't know myself, but the conclusions that others seem to be reaching is that yes, the high-mass stars by themselves could not have produced the ISM carbon in 13 billion years, they need some help from low-mass stars.

Thanks.

 

[qraal]

Obviously low mass stars, like the sun, are not major contributors to the interstellar carbon inventory, but, type II supernova are prime suspects. Progenitor stars' atmospheres are carbon rich and, when the core collapses, most of this carbon is dispersed into space.

There are more low mass stars than the big boys, but their evolution is slower too. Intermediate mass stars - like Sirius - probably disperse a lot more C & O during their late phases than previously believed, dredging up their guts and blowing that into the ISM.