Ryugu samples reveal traces of rock from before the Sun existed | Hacker News Reader

Ryugu samples reveal traces of rock from before the Sun existed

arstechnica.com

213 pointsBrajeshwar27 comments

really exciting stuff, waited years for this kind of news from that mission. I think its the case our solar system is only part of another previous solar system that went super nova. Finding information about that previous system is pretty cool

I think that all the elements present in the solar system that are heavier than hydrogen were made by previous stars and elements heavier that iron (or carbon I forget) were necessary made by stars that went supernova.

It would be very surprising if all these stars were not surrounded by rocky planets who themselves had volcanism and thus a process of rock creation.

Technically speaking big bang nucleosynthesis/baryogensis produced elements as heavy as lithium with some abundance, but yeah still dominated by hydrogen (and whatever other exotic non-baryonic .... stuff is out there)

- https://en.wikipedia.org/wiki/Baryogenesis

- https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis

Also, this is a great image showing the proportions of elements based on source

https://en.wikipedia.org/wiki/Chemical_element#/media/File:N...

That’s one of the cooler charts I’ve ever seen thanks for sharing. It’s wild that elements from merging neutron stars like iridium and uranium could even find us here. Sends home how old the universe is.

Find us here? Our solar system was created far far away from here. All the stuff that makes up our solar system was created by far older stars that long ago exploded and threw their material into space. Eventually some of that material coalesced into our Galaxy and our sun and planets.

So neutron stars collisions are actually responsible for a huge chunk of the elements in the periodic table!? Mind blowing.

How did they end up on the solar system after that? What we've got is just the material ejected when such cataclysmic collisions happen?

Do you have any books you could recommend on this subject?

It's not the sole focus of the book, but I recall "A Universe From Nothing" by Lawrence Krauss mentioning it a couple of times, particularly in the case that only that set of elements in exactly those proportions leads to the Big Bang as the primary theory of how it all began.

"The Story of Earth: The First 4.5 Billion Years, from Stardust to Living Planet" by Robert M. Hazen has a chapter about genesis of elements ( big bang, star formation, supernovae, planet formation, etc).

Or neutron stars colliding

Iron. See iron peak

pretty much all solar systems are remnants of the original first generation stars though, yeah? if the universe started with nothing but hydrogen, that was the source of the first gen stars, then it took those dying off to give us He,O,C, etc.

The one that gets me is the theory that Earth is at least a second generation planet. So, maybe Ryugu returned some of the material that survived from what made up the first gen planet(s) Earth was formed. The fact that Jupiter hasn't hoovered all of that up is also impressive.

Do we know, roughly and on average, which generation is our Sun? Is it only a second generation star? And how many generations should we expect to go through before we reach the black hole era and the heat death of the universe?

The sun is an “intermediate Population I” star, so relatively young (higher populations are older). Good overview of this topic:

https://en.wikipedia.org/wiki/Stellar_population

Does this mean we might theoretically find rock in asteroids that contains evidence of life from planets that existed before earth did? Fossils, even?

Even if the previous generation of star systems were teaming with life it would seem to be still incredibly unlikely to find fossilized life in asteroids. You have to think of how much rock there is in a planetary body vs how much would have ever been anywhere near something alive.

....i expect tardigrades

Our solar system is not made of material created by any particular supernova, but of interstellar medium enriched by any number of events that created and dispersed heavy elements over the eons. But the shockwave of a then-nearby supernova explosion may have been the catalyst that triggered star formation in the presolar nebula. The sun likely had many siblings born at roughly the same time, but most likely those aren’t anywhere near us anymore.

I don't have any evidence, but I dont think so at all. There is just too much heavy elements in our solar system to be made up of just the accumulation of dust out there. I think our material is mostly from a specific event

As far as I know, our stellar neighborhood is not anomalously rich in heavy elements compared to your standard issue cubic parsec of space. The Sun is a perfectly ordinary Population III star with the expected metallicity.

> Powerful winds blow the outer layers of these stars off until there is nothing left but a white dwarf.

This doesn’t sound like an accurate description of white dwarf formation. Or is it?

It's accurate. Stellar winds are the primary driver of mass loss for stars near the end of their lives. Asymptotic red giants have extremely voluminous and sparse atmospheres very loosely bound by gravity; any excess radiation pressure would create an instability and blow away portions of the outer envelope. Eventually this exposes a dense, glowing carbon/oxygen/neon core surrounded by a fraction of the original atmosphere (exact composition varies), which we call a white dwarf.

Further reading: Ch. 13, Carroll & Ostlie, Introduction to Modern Astrophysics

Would this be the oldest thing on earth?

Seems unlikely. I don’t have an estimate on hand but a significant percentage of the ~50 tons of material impacting earths atmosphere each day survives the trip relatively unharmed. It’s a surface are to volume ratio thing where small objects can avoid melting.

As such there’s presumably a lot of ancient material embedded in the Antarctic ice sheet etc. That said these samples are uncontaminated which greatly increases their scientific value.

No, but very close.

Wouldn't everything heavier than Iron be older? IIRC, gold for example is generated when stars go supernova, which implies all gold on Earth existed before the solar system formed.

Gold is a lot heavier than iron, so maybe the following does not apply to that but: We can't interpret such cutoffs as being strict.

I would say, reaction speed depends on the gap between energy available and energy required but there's a lot of environments where the reaction can still happen at a fractional rate even if the mean energy level is below the minimum required.

Iron is at the peak but in environments where it could be formed, slightly heavier elements could also be formed at a slow rate.

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