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Comment by XzAeRosho | Hacker News Reader

>The presence of oxygen so early in the life of this galaxy is a surprise and suggests that multiple generations of very massive stars had already lived their lives before we observed the galaxy.

For some reason this quote blew me away. It's just so hard to comprehend the timescales and vastness of the universe.

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Multiple generations is perhaps an overstatement. The first oxygen in the Universe came from what we call Population III stars which is the first generation of stars to form after the Big Bang and what separates these from other stellar populations is that they do not have elements heavier than hydrogen or helium (except for minuscule traces left over from the Big Bang but these are insignificant). Now we don't know much about Population III stars but many models predict they are massive and when they die, can release 60 times the mass of our sun in the form of oxygen. That's really a lot of oxygen so you don't need too many of these to go off to pollute the early Universe and probably one of the reasons why we haven't yet found Population III stars.

The word "generation" isn't really a thing in astronomy jargon. "Population III" is a population, and it includes stars formed after some supernovae, up to the point where the metals % gets high enough to be Population II.

Big stars burn hot and fast, the more mass, the shorter their lives

Pop III stars (if they existed) are really a mystery, we can't easily extrapolate. These stars would be purely hydrogen and helium so it would take them a surprisingly long time to get to CNO cycle, for example.

So I think it is fair to say they did exist. If we believe in Big Bang Nucleosynthesis then heavy elements had to come from somewhere making the first generation of stars (whatever their properties may be) be Population III. I agree that without a catalyst it's hard to initiate the CNO cycle but indeed models predict that it is possible even under these circumstances.

Why would it take a Pop III star longer than an equivalent-mass Pop I or II star to reach the end of its H / He fusion cycle?

Because of the lack of C, N, and O, which are catalysts in the CNO cycle. They aren't produced by it.

NB: based on some quick searches, it seems that low-metalicity Pop III stars would rely on the pp (proton-proton) fusion chain. That's going to slow reaction somewhat, and extend lifetime. But for high-mass stars with only a few millions of years expected lifetime in a Pop I/II class, that's ... still a relatively modest difference compared to the several hundred million year lifespan of the early Universe.

Or am I missing something?

Another interesting quirk of Pop III stars is that their initial mass function is expected to form much more massive stars than Pop II or Pop I. So even if Pop III stars are longer lived at the same mass as Pop II or Pop I, there will be a lot more supernovae per time, leading to fast enrichment and then Pop II.

That was one of my thoughts.

Another is that p-p fusion is fairly common. Look up when the Big Room's bright and you'll see a ... stellar example yourself ;-)

(p-p fusion dominates in stars < ~1.3 M, where M is a solar mass. CNO fusion is typical of more massive stars.)

Thanks!

It's interesting that [1] has a diagram showing that in 2022 the NASA diagram claimed that stars & galaxies formed 400M years ago so this feels like a big shift to having a massive galaxy already at 300M with data suggesting it's formed after several generations of stars.

> All of these observations, together, tell us that JADES-GS-z14-0 is not like the types of galaxies that have been predicted by theoretical models and computer simulations to exist in the very early universe

This is exciting. Maybe our understanding of the Big Bang is extremely flawed & this data is just the first inklings that we have to reimagine what we know about it?

> formed 400M years ago

do you mean formed 400M years after the big bang instead of 400M years ago from today? That's like yesterday to the Universe.

Correct. Obviously not 400 mya.

No. The diagram https://science.nasa.gov/resource/history-of-the-universe/ tells us that galaxies and dark matter formed 400M years after the big bang. Look at the right of the chart legend: "13.8 billion years" is above "today".

And this observed galaxy formed less than 300M years after the big bang. The chart is now wrong.

That's the beauty of theories in that they can be proven right or wrong. Thanks to the JWST, a lot of theories are needing to be updated. We're just now being able to actually test those theories. At some point, these types of charts will be updated.

As you stated, it is exciting times.

Very large stars live very short lives.

Our star will live 10 billion years, the smallest stars will last trillions of years, the largest stars live less than 10 million years and some very early stars broke the models for how big they were and maybe lived much less long.

What happens is their cores go through stages of fusing an element until they run out, gravity takes over and shrinks the core until the next element ignites, fuses, and runs out, down to iron. At one of those stages the collapse triggers a supernova (or one of the class of ways a star can die) instead.

The scale of both time and space are the least confusing things in our universe, to me at least.

This is ridiculous. Assumes that Oxygen only is created by stars. Oxygen is one of the most abundant elements created during LENR (Low Energy Nuclear Reaction, formerly known as Cold Fusion) experiments.

https://www.nature.com/articles/s41598-023-50824-8

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