this post was submitted on 12 Jan 2024
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Astronomy
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How is this different from a nebula?
From my amateur understanding of space, it seems to be a galaxy made of just primordial hydrogen and helium, back before the first stars formed and started creating heavier elements due to the fusion reactions that power stars and the eventual supernovas that further dispersed and helped to create even more heavy elements.
Another cool theory is that the first stars are thought to have been much, much more massive, possibly up to around a thousand solar masses since they were made solely of hydrogen and helium. It's estimated that current stars couldn't get above a few hundred solar masses at most due to the existence of heavier elements in modern gas clouds. I don't understand enough to explain why the existence of heavier elements limits star size so I'll leave that to someone smarter than me.
Someone correct me if I got anything wrong, again I only have an amateur level of understanding about space.
The amount of heavy elements present in a star when it formed will be neglible to the amount that will be created over time through fusion.
You can actually detect this through spectroscopy because the initial amount of metals will be present in the outer layer of the star. Heavy elements made through fusion will be mostly in the core.
The reason stars formed from primordial gas, i.e. only consisting of hydrogen and helium, is that such a gas will fragment less as it cools and collapses. Less fragmentation means heavier stars.
I only have a high level knowledge of the process though.