[jeffreyH (OP)]

Was the sun formed exclusively from hydrogen and helium, just hydrogen or some heavier elements?

[syhprum]

The gaseous cloud from which the Sun and planets formed contained a small proportion of heavier elements from supernova events

[RD]

Some of the elements in the sun are detectable from its spectrum ...
https://en.wikipedia.org/wiki/Fraunhofer_lines#Naming
They include elements which are too heavy to have been made in our Sun.

[jeffreyH (OP)]

That leads to a different question. The very first stars in the universe could not have contained heavier elements and must have burnt fast and exploded in supernova. Was there enough time for enough of these to seed the whole universe with heavier elements?

[evan_au]

It is thought that the Big Bang would have produced a mix of elements something like:

mass abundances of about 75% of hydrogen-1, about 25% helium-4, about 0.01% of deuterium and helium-3, trace amounts (on the order of 10⁻¹⁰) of lithium, and negligible heavier elements.

Hydrogen and Helium do not radiate energy well, which would have resisted gravitational collapse into stars.

It is thought that the first stars (a hypothesized group dubbed "Population III") would have been very massive, as only a very intense gravitational self-attraction could overcome the internal pressure of hot hydrogen & helium. Such stars would have burnt all their fuel very rapidly and exploded as a supernova, seeding the cosmos with heavier elements.

Later stars (Population II) and today's Population I stars tend to be much smaller, with much higher proportions of heavier elements.

See: https://en.wikipedia.org/wiki/Stellar_population#Population_III_stars

[puppypower]

Some of the elements in the sun are detectable from it's spectrum ...
https://en.wikipedia.org/wiki/Fraunhofer_lines#Naming
They include elements which are too heavy to have been made in our Sun.

The thing I don't understand is how can humans make heavier elements than the sun, using only mild earth conditions, yet also assume the sun, with far more extreme conditions can't do squat? Is it because humans can use fission and fusion, while we only allow the sun to use fusion, so we can cheat and play god?

In modern times, the most important star making material is water; H2O. Water is composed of Hydrogen, which is the  most abundant atom of the universe and oxygen which  is number three. Water contains hydrogen in a form that is easier for gravity to influence; hydrogen bonding. Water is also the second most abundant molecule in the universe and exists primarily as ice crystals.

Water is also useful to star formation because water expands when it freezes and contracts when it melts. In terms of star formation, a cloud of ice being compressed by gravity will eventually heat until the melting point is reached. The 10% loss of volume, as the ice melts and becomes liquid, can cause an affect I like to call fusion hammer. It creates a secondary collapse which helps induce fusion via D2O. No other material, abundant enough to form stars, does the fusion hammer dance.

[jeffreyH (OP)]

It is thought that the Big Bang would have produced a mix of elements something like:

mass abundances of about 75% of hydrogen-1, about 25% helium-4, about 0.01% of deuterium and helium-3, trace amounts (on the order of 10⁻¹⁰) of lithium, and negligible heavier elements.

Hydrogen and Helium do not radiate energy well, which would have resisted gravitational collapse into stars.

It is thought that the first stars (a hypothesized group dubbed "Population III") would have been very massive, as only a very intense gravitational self-attraction could overcome the internal pressure of hot hydrogen & helium. Such stars would have burnt all their fuel very rapidly and exploded as a supernova, seeding the cosmos with heavier elements.

Later stars (Population II) and today's Population I stars tend to be much smaller, with much higher proportions of heavier elements.

See: https://en.wikipedia.org/wiki/Stellar_population#Population_III_stars

So hydrogen and helium alone are very bad for star formation. I am going to be thinking more about this.

[chiralSPO]

The thing I don't understand is how can humans make heavier elements than the sun, using only mild earth conditions, yet also assume the sun, with far more extreme conditions can't do squat? Is it because humans can use fission and fusion, while we only allow the sun to use fusion, so we can cheat and play god?

I think the main difference is that we have a much richer palette to begin with--the sun is >70% hydrogen, and only has impurities of other elements, while the earth has rich deposits of carbon, nitrogen, oxygen, sulfur, silicon, phosphorus and many metals like magnesium, aluminum, iron, titanium, as well as traces of elements that were formed by stars much more massive and violent than the sun (like platinum, rhodium, uranium etc.) which we have been able to use to do pretty much anything "impressive".

[chiralSPO]

It is thought that the Big Bang would have produced a mix of elements something like:

mass abundances of about 75% of hydrogen-1, about 25% helium-4, about 0.01% of deuterium and helium-3, trace amounts (on the order of 10⁻¹⁰) of lithium, and negligible heavier elements.

Hydrogen and Helium do not radiate energy well, which would have resisted gravitational collapse into stars.

It is thought that the first stars (a hypothesized group dubbed "Population III") would have been very massive, as only a very intense gravitational self-attraction could overcome the internal pressure of hot hydrogen & helium. Such stars would have burnt all their fuel very rapidly and exploded as a supernova, seeding the cosmos with heavier elements.

Later stars (Population II) and today's Population I stars tend to be much smaller, with much higher proportions of heavier elements.

See: https://en.wikipedia.org/wiki/Stellar_population#Population_III_stars

So hydrogen and helium alone are very bad for star formation. I am going to be thinking more about this.

Yes, the simple elements have very few electronic transitions so conversion of kinetic energy (temperature) to EM radiation is slow and ineffective below a certain temperature (you need enough thermal energy to make the atoms glow when they hit--and due to the spacing of the energy levels in hydrogen, cooling below about 1000 K (ca . 700 °C) is difficult.

[puppypower]

The thing I don't understand is how can humans make heavier elements than the sun, using only mild earth conditions, yet also assume the sun, with far more extreme conditions can't do squat? Is it because humans can use fission and fusion, while we only allow the sun to use fusion, so we can cheat and play god?

I think the main difference is that we have a much richer palate to begin with--the sun is >70% hydrogen, and only has impurities of other elements, while the earth has rich deposits of carbon, nitrogen, oxygen, sulfur, silicon, phosphorus and many metals like magnesium, aluminum, iron, titanium, as well as traces of elements that were formed by stars much more massive and violent than the sun (like platinum, rhodium, uranium etc.) which we have been able to use to do pretty much anything "impressive".

The inner planets of our solar system are rocky and contain all these larger elements. The outer planets are more gaseous. If you extrapolate, the sun should have substantial heavier elements being closer to the rocky planets than the gaseous ones. it should have the most heavy elements being number one in the alignment.

The denser and heavier elements, from super nova remnants, would be the most likely to form the nucleation core of the collapsing dust and debris cloud, from which the solar system would form. This heavy atom core becomes the sun.  Now the sun has the same precursors as the earth. 

Another conceptual concern is say we assume the solar system formed from super nova remnants. If our solar system, via the sun is mostly hydrogen, why did the original star go supernova, if there was still so much hydrogen left over? One possible explanation is the extra hydrogen was on the surface, and not readily available to the core, so the core was fooled into thinking it is out of fuel. 

If the excess hydrogen was on the outside, the blast profile should project these light materials furtherest out, while the heavies that from form the blast, would stay closer. If the nucleation center of the solar system is based on heavies and most of the hydrogen has been blasted farthest away, how does the sun get the hydrogen? It was already concluded that hydrogen and helium has too much entropy to form the nucleation center.

I tend to think that the discovery and idea of a supernova was so intoxicating, that many have become love blinded. It sort of like falling in love, and seeing what we want to see in your beloved, which may not always have the same logical consistency, without the rose colored glasses.

[chiralSPO]

The thing I don't understand is how can humans make heavier elements than the sun, using only mild earth conditions, yet also assume the sun, with far more extreme conditions can't do squat? Is it because humans can use fission and fusion, while we only allow the sun to use fusion, so we can cheat and play god?

I think the main difference is that we have a much richer palate to begin with--the sun is >70% hydrogen, and only has impurities of other elements, while the earth has rich deposits of carbon, nitrogen, oxygen, sulfur, silicon, phosphorus and many metals like magnesium, aluminum, iron, titanium, as well as traces of elements that were formed by stars much more massive and violent than the sun (like platinum, rhodium, uranium etc.) which we have been able to use to do pretty much anything "impressive".

The inner planets of our solar system are rocky and contain all these larger elements. The outer planets are more gaseous. If you extrapolate, the sun should have substantial heavier elements being closer to the rocky planets than the gaseous ones. it should have the most heavy elements being number one in the alignment.

The denser and heavier elements, from super nova remnants, would be the most likely to form the nucleation core of the collapsing dust and debris cloud, from which the solar system would form. This heavy atom core becomes the sun.  Now the sun has the same precursors as the earth. 

The sun certainly has heavy elements in it--much more than the earth has. But the key here is the concentration. The earth is almost 35% iron by mass, while the sun is less than 0.15% iron by mass.

Another conceptual concern is say we assume the solar system formed from super nova remnants. If our solar system, via the sun is mostly hydrogen, why did the original star go supernova, if there was still so much hydrogen left over? One possible explanation is the extra hydrogen was on the surface, and not readily available to the core, so the core was fooled into thinking it is out of fuel. 

I am not an expert in star formation or cosmology, but my understanding is that the mass of any single supernova is a tiny fraction of the mass in the region of space that it showers its guts across, and that because most of the atoms in the universe are hydrogen (and some helium), the next generation of stars will still be mostly hydrogen (and some helium), and only be enriched a little bit with the emissions from the supernova.

If the excess hydrogen was on the outside, the blast profile should project these light materials furtherest out, while the heavies that from form the blast, would stay closer. If the nucleation center of the solar system is based on heavies and most of the hydrogen has been blasted farthest away, how does the sun get the hydrogen? It was already concluded that hydrogen and helium has too much entropy to form the nucleation center.

A) the sun was not the center of any blast, our metals are from distant supernovae.
B) The amount of hydrogen a body has is largely determined by its mass and temperature. The sun is very hot, but it is also very massive, enough so that the hydrogen only escapes very slowly. The gas giants in our system are not nearly as large as the sun, but are still quite massive, and very cold. The inner planets and asteroid belt are too small and warm to have held on to their H₂, which was either captured by the sun, or blasted away by the solar wind.

I tend to think that the discovery and idea of a supernova was so intoxicating, that many have become love blinded. It sort of like falling in love, and seeing what we want to see in your beloved, which may not always have the same logical consistency, without the rose colored glasses.

I suppose you would know something of intoxicating phenomena/theories--you seem quite taken with water and entropy yourself! 

[evan_au]

The thing I don't understand is how can humans make heavier elements than the sun, using only mild earth conditions, yet also assume the sun, with far more extreme conditions can't do squat?

Yes, humans have been able to produce elements heavier than Uranium, by using particle accelerators to smash together heavy elements like lead. This is a form of nuclear fusion, 1 atom at a time, ie it takes a phenomenal amount of energy to create one atom of Livermorium (element 116).
- But we didn't make the lead and uranium - these were already present when the Earth formed.

The temperature of a substance is a measure of the average kinetic energy of its particles. The interior of the Sun has a temperature of around 17 million degrees, which represents a very high velocity for a hydrogen nucleus, but still a non-relativistic velocity
- Even early particle accelerators could accelerate ions to velocities where relativistic effects become significant, which is equivalent to temperatures far higher than the interior of the Sun

The Sun is fusing hydrogen (1 proton) into Helium, using temperatures of around 17 million degrees. Humans have only produced uncontrolled fusion in a Deuterium/Tritium mixture, which has a far lower ignition temperature than normal Hydrogen.

In modern times, the most important star making material is water; H2O.

If we consider the Sun a "modern" (Population I) star, that would imply that the Sun's mass is over 80% oxygen. In fact it is slightly under 1% by mass. So water was not an important star-making material for the Sun.
See: https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements#Universe
The chemical abundance of elements in stars is about 73% hydrogen today - and this ignores vast clouds of neutral hydrogen which are raining down on to galaxies and driving star formation. These are hard to detect spectroscopically, but can be detected by the Lyman Alpha Forest, see:
https://en.wikipedia.org/wiki/Lyman-alpha_forest#Use_as_a_tool_in_astrophysics

If the excess hydrogen was on the outside

This depends on how well the star is mixed by convection. Stars with extensive convection will burn all their hydrogen to Helium.

metals like magnesium, aluminum, iron, titanium, as well as traces of elements that were formed by stars much more massive and violent than the sun (like platinum, rhodium, uranium etc.)

Nuclear fusion in massive stars can produce elements up to iron and nickel.
Elements slightly heavier than nickel can be formed during the fury of a supernova - but nothing as heavy as uranium.
It is thought that most elements heavier than gold were sprayed into space as neutron stars collided - just such an event was detected this year by the LIGO+VIRGO gravitational wave detectors. Astronomers announced that they had seen a light curve consistent with the decay of radioactive gold.
See: https://en.wikipedia.org/wiki/Stellar_nucleosynthesis#Key_reactions

[Bored chemist]

That leads to a different question. The very first stars in the universe could not have contained heavier elements and must have burnt fast and exploded in supernova. Was there enough time for enough of these to seed the whole universe with heavier elements?

Clearly, yes, thee was.

[jeffreyH (OP)]

I was thinking it may not have been the primary mechanism.

[chiralSPO]

I was thinking it may not have been the primary mechanism.

Can you elaborate?

[jeffreyH (OP)]

Sorry, I missed your reply. Well in a supernova explosion the debris will be ejected spherically. As the sphere of debris expands its density drops. The distances involved in the distribution of this material means that only a tiny proportion of heavier elements will reach any remote system and take maybe thousands or hundreds of thousands of years to do so. The formation of stars would likely happen much sooner than when this material arrives. So the stars themselves may well be depleted in heavier elements. The planets that are still forming are more likely to benefit from this as surface coatings. This still does not explain the iron cores of planets.

The only reasonable explanation would be that supernovas were the norm in the very early universe. However, this would mean far more heavy elements present in stars such as the sun. So there may be a conundrum here.

[jeffreyH (OP)]

You could always say that the solar wind from a star would drive away heavier elements back into planet forming disks.

[chiralSPO]

Sorry, I missed your reply. Well in a supernova explosion the debris will be ejected spherically. As the sphere of debris expands its density drops. The distances involved in the distribution of this material means that only a tiny proportion of heavier elements will reach any remote system and take maybe thousands or hundreds of thousands of years to do so. The formation of stars would likely happen much sooner than when this material arrives. So the stars themselves may well be depleted in heavier elements. The planets that are still forming are more likely to benefit from this as surface coatings. This still does not explain the iron cores of planets.

The only reasonable explanation would be that supernovas were the norm in the very early universe. However, this would mean far more heavy elements present in stars such as the sun. So there may be a conundrum here.

It may well be that the radius of enrichment is only a few light years (if we know how much carbon is flung out of a supernova, and we know the carbon content of the sun (assuming it is second generation--I don't know how many supernovae worth of carbon the sun may have...), we can estimate the distance from the supernova, assuming it is the only source of carbon.

I believe that there are localized parts of the galaxy (and presumably others) where many stars are formed. These so-called nurseries may well be fed by local supernovae. (I took a cosmology course a really long time ago, so some of this might be out of date or misremembered, but also seems to be in line with what wikipedia says: https://en.wikipedia.org/wiki/Star_formation ).

My understanding is that the young stars fling each other out of the nest (along with some clouds of what will eventually be their planets, moons, asteroids, comets etc.).  These solar systems then find their own orbit within the galaxy. Some people believe that our sun was formed in the open cluster M67

[jeffreyH (OP)]

Thanks. That does make sense.

[evan_au]

So the stars themselves may well be depleted in heavier elements.

Massive stars can produce elements up to iron by nuclear fusion. Less-massive stars (like the Sun) are unlikely to produce any element beyond carbon.
The large stars that undergo a supernova are likely to end up as neutron stars or black holes.
So they are severely depleted in all normal elements - both light and heavy.

The planets that are still forming are more likely to benefit from this as surface coatings.

There is a suspected instance of this - there are deposits of Iron-60 in a thin layer on the Pacific seafloor.

Iron-60 is expected to be produced in a supernova, and has a half-life of 2.6 million years.
See: https://en.wikipedia.org/wiki/Near-Earth_supernova#Past_events

This still does not explain the iron cores of planets.

Planets and dwarf planets are defined by their ability to pull themselves into a spherical shape.

Any object having this level of mass will be severely heated and melted by the collisions of the planetesimals from which it formed, plus radioactive decay from Uranium and Thorium (these heavy elements are formed in neutron star collisions, rather than supernovae).

In a molten body, the denser material is likely to sink to the center, forming a nickel-iron core.
See: https://en.wikipedia.org/wiki/Planetary_differentiation

In 2023, a space probe is planned to be sent to the asteroid Psyche, which appears to be the metallic core of an asteroid.
See: https://en.wikipedia.org/wiki/Psyche_(spacecraft)