[puppypower (OP)]

When I was a boy, just beginning to become interested in science; 1960's, the theory of that time was the sun could make all the atoms of the periodic table, including even bigger unstable atoms. This POV was based on the wisdom of the old timer Physics, that brought us atomic and hydrogen bombs, breeder reactors and nuclear energy, all of which were test proven.

Somewhere between then and now, the sun was demoted in ability, and now the theory is the sun can only fuse smaller atoms. Now we need supernova to make higher atoms for the sun. Why the change?

[evan_au]

the theory of that time was the sun could make all the atoms of the periodic table, including even bigger unstable atoms.

Perhaps what you remember is that "stars" can make lots of elements - but it has been known for some time that the Sun is too small to produce any elements higher than carbon - and it is too small to become a supernova. 

It has been known for many years that no star can make energy by fusing anything heavier than iron or nickel - just look at a graph of binding energy per nucleon - it's all downhill after this plateau.  Hoyle showed this, between 1946 and 1954.

The very high pressures that occur during a supernova, and the bombardment of the debris by high-energy neutrons and protons can synthesize some elements beyond nickel. However, it is now considered that the neutron intensity in a supernova is too low to produce the observed concentration of elements heavier than gold.

It is now thought that elements heavier than gold (including radioactive elements beyond uranium) might be sprayed into space during neutron star collisions. Perhaps with gravitational-wave detectors we may soon be able to spot some of these events as they occur?

Why the change?

Some of these changes were before my time, so I can't really comment on the timing.

With particle accelerators, we now have a better idea of the mass, lifetime and decay modes of various isotopes, and how they interact under high-energy collisions.

The calculations are complex, but now we have computers that are powerful enough to model more of the effects during a supernova. This has been assisted by the detection of a burst of neutrinos from a supernova.

Before the discovery of pulsars, neutron stars were somewhat hypothetical, but now they are a force to be reckoned with in the galaxy.

[puppypower (OP)]

The problem with particle accelerator data, is this data is generated at high energy/temperature. However, it uses low gravitational pressure. Accelerators do not operate under the full range of pressures we see in the core of the sun. Therefore this data is really an isobar at low pressure, on a much larger phase diagram, that has additional phases.

As an analogy, in the phase diagram of water below, particle accelerators data are analogous to a vertical line; isobar, at low pressure. For example, we start at low temperature at 10 GpA and with each new generation of particles accelerators we go vertical to 2000 C. However, we don't fill in the entire diagram at extreme pressures;10-100 GPa. Much more work needs to be done.

The bottom line is you can't extrapolate extreme pressure phases and phase changes from low pressure data. Water X is connected to metallic water, which you can't predict from a 10 GPa isobar no matter what the temperature range.



Why do you think gravity is not cooperating in unified theories? Gravity generates pressure and not just changes in space-time. It does not work under only low pressure isobaric conditions.

The particle accelerator data, at least to me, simulates the aftermath of an exploding star, after the material has been accelerated into space, and reduced in pressure; moving close to the speed of light. I can sort of see why a super nova model is being used since the data will work here; particle accelerator isobar. However, you can't extrapolate this data to the core of the sun. This is an example of the data cart leading the horse.

Humans can make atoms larger than 92 in the periodic table, in the lab. The synthetic atoms are show in the periodic table below in pink. The idea that man can do this in the lab, but the sun needs special help from outside, does not make any sense if you include extreme pressure.




 

[evan_au]

Humans can make atoms larger than 92 in the periodic table, in the lab. ... The idea that man can do this in the lab, but the sun needs special help from outside, does not make any sense if you include extreme pressure.

The hydrogen nucleus has a charge of +1. It is pretty easy to work out what temperature and pressure you need to add another proton to form Helium - and to measure how long this unstable isotope it will last. This mix of pressure and temperature and time is called the Lawson Criteria. Scientists are not ignoring pressure as a vital ingredient in nucleosynthesis!

Potassium has a charge of +19. It is pretty easy to work out what temperature and pressure you need to add another proton to form Calcium - and to measure how long this unstable isotope it will last. And it is a lot higher temperature and/or pressure than you need to achieve Hydrogen fusion.

A small increase in the mass of a star results in a big increase in its core temperature, and in the rate that it burns its fuel. A star with more fuel lasts less time than a star with less fuel!

That's why higher elements in the periodic table (up to iron) can be produced in more massive stars, and not in the Sun.

[puppypower (OP)]

How do they make the higher elements beyond 92 in the lab, without supernova pressures? The labs show there are other possible paths.

I have a theory that allows the sun the build atoms higher than expected by contemporary theory. The foundation of the theory is that larger atoms are less dense than smaller atoms at extreme temperatures and pressures. The reason is the smallest atoms will ionize fully, whereas the largest atoms will retain inner electrons; for any given ionization energy.

Density is mass/volume. A smaller fully ionized atom uses nucleus volume for its density, while a larger partially ionized atom uses atomic/plasma volume for density, which is much larger. The impact of the inner electrons is larger atoms will define larger volume; lower density.

The analogy is an iron ship can float on water even though iron is denser than water. The reason is the hull of the ship adds volume to the iron lowering the average affective density of the iron; ship. In the case of partially ionized larger atoms, the hulls of the heavy atom ships are the inner electrons. These will float on top of a sea of smaller denser fully ionize fuel atoms.

The net affect is the fusion core of a star will be composed of fully ionized smaller atoms, surrounded by a shell of partially ionized larger atoms. This heavy atom shell has advantages. If the fusion core gets too hot, the extra heat ionizes electrons in the heavy atom shell causing it to get denser, so it sinks and seals the core, restricting fuel diffusion. This prevents runaway fusion. As the core cools, due to restricted fuel, more electrons are added to the atoms of the shell so the shell expands and floats higher, allowing easier fuel diffusion, allowing fusion to surge again.

The observations of sun spots and solar flares, suggest the shell restricted cooling and heating off the core is done somewhat locally instead of globally.  A surge of fuel, followed by a local fusion surge, creates a phenomena that I will call fusion hammer, where a high energy solar flare foundation, pounds against the heavy atom shell to generate extreme local pressure, for the formation of higher atoms.

The result of the fusion hammer is the floating shell gets thicker over time. This can result in more global fuel diffusion problems than can cause the entire core to cool. Periodically, a star will needs to clean the pipes, using a massive back draft fuel blast, that  will blast off parts of the shell and entrained materials into space, to form planets, moons and asteroids.

[JoeBrown]

The change has to do with statistical fine tuning of models.

Personally I imagine heavier elements than carbon occasionally fuse in the sun.  The statistical models show that when the bulk of the mass fusion is to iron and heavier, the energy produced doesn't support pressure to maintain stability.

TV programs (Science shows) have a tendency to draw a finite line at iron.  But I'd venture to say the line is a little bit fuzzier than that.  There is a range of densities in every star.  The pressures at the center can and frequently form heavier elements.  Statistically the amounts would be small in comparison to the bulk/majority of the fusion process.  However inside a solar mass, extreme gravity and time dilation also causes the heavier elements to fission (decay) faster than we experience on Earth.  (I read the closer to the sun or orbit takes us, the faster nuclear fission processes occur, which can have devastating consequences to radiation applicatons).

So in essence, I fathom the sun does fuse atoms to heavier elements still, but statistically its a lot less than once accepted.

[evan_au]

inside a solar mass, extreme gravity and time dilation also causes the heavier elements to fission (decay) faster than we experience on Earth.

I am afraid that this is a reversed understanding of Einstein's general relativity.

In the strong gravity well of the Sun, time moves more slowly. This means that:

• a "clock" will tick more slowly when it is deep in a gravitational well.
  
• the closest point in Mercury's orbit slowly changes over the centuries
  
• if you consider nuclear decay to be a kind of "clock", you would expect it to tick more slowly in a deep gravitational well (rather than faster).
• This applies even more strongly in the even more extreme gravity wells of more massive stars, neutron stars and black holes

I read the closer to the sun our orbit takes us, the faster nuclear fission processes occur, which can have devastating consequences to radiation applications.

I occasionally hear suggestions that some nuclear processes might occur more rapidly at various times of the year.

It is a bit hard to prove with Earth-bound experiments, since at present the eccentricity of Earth's orbit is only 1.6%. Any small variation in nuclear reaction rates would be automatically compensated by control loops in nuclear reactors.

At this time, you would have to say that this effect is at best a hint, and not proven (to the extent that it is published in a peer-reviewed physics journal). There is a Nobel Prize waiting for the person who proves it!

[Bored chemist]

It's important to recognise that the sun isn't very god at doing fusion.
It's been going for billions of years and hasn't even got half way to finished yet.
On a weight for weight basis , the sun produces less heat than a compost heap.
So, since it's not good at doing the sort of thing it can do- producing helium- it's a bit of a stretch to see it making much of the heavier elements.

[JoeBrown]

Thanks Evan,

Knew time was skewed by GR but not which way.  DOH

Seems a safe assumption that heavier atoms exist inside the sun and likely true of all bodies in this here solar system.

I speculate all gas giants likely possess more mass than the Earth consisting of atoms heavier than helium.  Quantity and distribution are a tad bit difficult to contemplate.  But seems reasonable Jupiter may have started out as a very big chunk of spent star, Saturn, Uranus and Neptune.   Sol may or may not have started that way, but seems reasonable a lot of heavy elements found their way into that body of gravity, due to attraction.

Seems likely that the matter from our previous generation star met with an independent cloud of gas that hadn't fully collapsed.  Maybe it was on its way to collapse and hurried along or was interrupted..  More likely the shock wave caused it to collapse and there had to be enough mass to contain mass from the explosion.

Seems like we're so far from any other star, it doesn't seem possible, yet here we are.

I don't know how I missed that time goes slower in a concentrated mass repository.  Guess spegettification is too distracting, for me to grip time slowing, stopping or reversing.  Now it makes sense that black holes be suspected as a means to go back in time.

[evan_au]

Seems a safe assumption that heavier atoms exist inside the sun and likely true of all bodies in this here solar system.

The Sun is mostly hydrogen and helium, but there are tiny amounts of heavier elements like iron.

In the 1920s, it was assumed that the Sun had the same chemical composition as the Earth (oxygen, silicon, iron, etc, just hotter), but Cecilia Payne showed that the abundance of Hydrogen and helium were enhanced by a factor of a million or so.

It is assumed today that the Sun and all of the planets condensed out of a single protoplanetary disk, so they are all made from the same basic mix of elements. 

I speculate all gas giants likely possess more mass than the Earth consisting of atoms heavier than helium.  Quantity and distribution are a tad bit difficult to contemplate.

Actually, like the Sun, the gas giants are predominantly hydrogen and helium. Only a tiny fraction of their mass comes from elements heavier than helium (although these minority elements do create Jupiter's amazing swirls of color).
 
Starting from the same basic mix of materials, lighter blobs (like Earth or Mars) could not hold onto lighter gases like hydrogen and helium, while heavier blobs (the Sun and gas giants) did hold onto the original hydrogen/helium-dominated composition.

There are also differences due to temperature - hot locations like Mercury could not hold onto heavier gases like nitrogen, while colder places like the the Earth did; really cold locations like comets in the Oort cloud could hold onto gases like nitrogen, despite their much lower mass.

See: https://en.wikipedia.org/wiki/Protoplanetary_disk

[puppypower (OP)]

Humans have made elements 93-112 in the lab. These are all very highly endothermic reactions. How was this possible without a supernova?

[chiralSPO]

Humans have made elements 93-112 in the lab. These are all very highly endothermic reactions. How was this possible without a supernova?

These elements were synthesized in quantities of about 100 atoms at a time using powerful particle accelerators.

[JoeBrown]

Starting from the same basic mix of materials, lighter blobs (like Earth or Mars) could not hold onto lighter gases like hydrogen and helium, while heavier blobs (the Sun and gas giants) did hold onto the original hydrogen/helium-dominated composition.

Even thought heavier elements are only tiny fraction of total composition of giant balls of gas, it doesn't preclude that they do not contain more mass of heavier elements than Mercury, Venus, Earth and/or Mars.

They're giant because they're made of a lot of stuff.  I suspicion it's likely their proto-planet beginnings were culminated from being bigger chunks of iron, etc.   No proof, it only seems logical to me.

It is assumed today that the Sun and all of the planets condensed out of a single protoplanetary disk, so they are all made from the same basic mix of elements.

 
Not the current complete accepted thesis.

Its believed all the heavier elements were synthesized in previous generation star(s).   Even tho the heavier elements are in the minority of mass, its evident that Mercury, Venus, Earth and Mars are composed of predominantly heavy elements, with such origination.

The age of the Sun and the Earth are estimated to be about 4.5 billion years old.  If the materials from supernova explosion and the central gas giant holding us in orbit formed at roughly the same time... 

It suggests a shock wave of mass from a supernova episode caused our protoplanetary gas disk or cloud to collapse.

Its all kinda sketchy to me.  But to account for the amount of heavier elements found here, only a couple of plausible explanations seem feasible.

Either the sun had to catch mass in orbit at/when it formed or formed the same time as the explosion, later caught the mass.

In order to retain the heavy elements, I think the mass had to collide with a cloud and likely cause it's collapse.

The sun could have captured mass after formation, but the timing seems a little too coincidental.

Seems really foreign to me that we are the product of something like the horse head nebula, that existed in a similar state long, long ago.