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Comment by ajross | Hacker News Reader

Actually current modeling has supernovae as being only a small contributor to the measured abundance of heavy nucleii. These guys tend to come from a more exotic source still: material thrown off as a neutron star is tidally disrupted during a merger event with another neutron star or black hole.

The wikipedia page is pretty good, as always: https://en.wikipedia.org/wiki/Nucleosynthesis

Almost everything with mass of 90 or above comes predominantly from neutron star mergers, basically.

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Good Lord the universe is old. To think of how rare all that must be and how it had to have time to somehow get here to our planet.

If they weren't here, we wouldn't be able to talk about it.

I'd be interested to know if we're in an element rich vein of the wider universe or if all the good stuff is more or less evenly distributed?

I'm not sure but this has some interesting info such as-

>Some whole galaxies have average metallicities only 1/10 of the Sun's. Some new stars in our galaxy have more metals in them than the original solar nebula that birthed the Sun and the planets did. So the amount of "metals" like oxygen and carbon can vary by a few orders of magnitude from star to star, depending upon it's age and history.

https://www.reddit.com/r/askscience/comments/9tujxn/are_the_...

Phosphorus is supposed to be rare in the wider world. Considering how central it is to everything important, life might find it very difficult to start in our temperature range, without.

After all, is there anything better to create new elements than a hot, dense neutron soup?

I'm always fascinated by the sheer and unfathomable amounts of energy that is thrown around in these events. Just thinking about the fact that a single spoonful of neutron star matter contains more mass than Mount Everest fills me with wonder about the world we live in.

What happens whena tablespoon of neutron soup gets thrown out of the well of a neutron star? Does it suddenly expand to the size of everest? Where do the electrons come from?

I'd imagine some of the energy and degenerate matter consisting of neutrons would convert to protons and electrons, and nucleosynthesis would take place to form elements.

I have no idea, though, but I'm pretty sure I watched a video about this.

In terms of "where do the electrons come from", an ordinary neutron in free space has a half-life of about 10 minutes, decaying through beta decay which produces a proton, an electron and a neutrino.

That sounds fairly energetic... So after 10min you'd have some odd mix of heavy elements probably approaching a decent fraction of the volume of everest. Half the volume of everest x (densityofgranite / densityoflead)

That kind of expansion rate has to rival any explosion imaginable.

It's essentially a giant atomic nucleus, so absent a star's worth of gravity holding it together it's going to decay rapidly into stable isotopes. So essentially it would act more or less the same as a huge fission bomb of the same mass.

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