Creating Elements after BB: Where did the Supernova's Go?(Vanity)

NA | 2007/02/15 | Robert A. Cook

[RadioAstronomer]

I thought Sol was a third generation star

Since a "generation" of stars can range from a few milllions to many billions of years, the concept of "second" or "third" generation isn't really applicable to the Sun. The first stars formed in the galaxy about 14 billion years ago, and the Sun was formed 4.6 billion years ago. Many "generations" of massive stars, and several generations of intermediate mass stars, contributed to the formation of the Sun.

[ml/nj]

I don't know anyone over age 18 who flaunts their SAT score like the size of their phallus.

See, the crowd I hang out with is more interested in intellectual ability than the size of someones schwanz. But I guess it takes all kinds.

ML/NJ

[Robert A Cook PE]

Thank you for the reference.

[Physicist]

You know, I've been puzzling and puzzling over your post, and while most of it doesn't make sense to me, I think I may have come to understand the root of your problem.

You aren't so much concerned with how the heavy elements get created, but with how they got scraped back up together again to form our solar system. Right?

If that is your concern, you may be interested in this calculation I performed almost six years ago on FR.

Here's the executive summary: given a cloud of arbitrary size that has a density as low as any found in the galaxy (one hydrogen molecule per cubic centimeter), how long does it take for the cloud to collapse completely? The answer is 700,000 years. Less than a million years. A cosmological eyeblink. Denser clouds will collapse even faster.

So if you have a supernova going off every 30 years or so, let them spread their heavy nuclei as thinly as you like across the galaxy. Gravity will have no problem collecting them up again in a very short time, whenever it has the chance. All it takes is a local density fluctuation to start the process, and the trace residues of a million supernovae--now evenly spread throughout the galaxy--will condense to form a solar system.

Another suggested Google search term: Jeans Instability

[Robert A Cook PE]

Thank you. Marked for review tonight.

[<1/1,000,000th%]

When the sun reaches it's asymptotic giant branch star phase, it will certainly create carbon, but in general you're correct. Through most of its lifetime the sun can't generate anything close to a heavy nuclei.

However, I think you're on to something. At some point in the universe's development it became too big to scatter heavy nuclei everywhere we see them now. I think your approach could be used to set limits on when the heavy nuclei must have been created and what kind of stars must have created them.

The approach I was trying to suggest was to look at the stars in the early universe to determine how many heavy nuclei they could've created. Current ideas suggest that early stars were enormous. They should have been able to get close to producing heavy nuclei before going nova and scattering heavy nuclei all over the neighbor hood.

You're much better suited to make the calculations than I am since you've had some experience calculating cross-sections for fusion reactions.

Using this approach it might be possible to set limits on the size of the stars in the early universe, possibly to determine which came first, galaxies or central galactic black holes, maybe even set limits on the size of galactic black holes, and to set limits on the time when heavy nuclei would have had to be generated to create the distribution we see now.

[Robert A Cook PE]

The penalty, of course, to assuming super-heavy stars very early in the universe is that you generate black holes (after the supernova) that tend to recapture the ejected material.

Alternate: If the superstar dust cloud mass is enough to form a black hole, and the dust cloud collapse time is as short as indicated above (< 3/4 million years) then what would prevent the black hole from forming before or during stellar evolution: at a period when all of its material would go down the hole and none be available for ejection?

We still would assume that the time, heat and pressure to go from first fusion (H + H and H - D, etc) to second generation fusion ... up to the final layer is not enough to overcome the black hole limits of gravity and distance.

[Physicist]

The penalty, of course, to assuming super-heavy stars very early in the universe is that you generate black holes (after the supernova) that tend to recapture the ejected material.

A black hole has no more ability to recapture the ejecta than any other body of the same mass. The gravitational field is the same outside of the radius of the pre-collapse core.

Alternate: If the superstar dust cloud mass is enough to form a black hole, and the dust cloud collapse time is as short as indicated above (< 3/4 million years) then what would prevent the black hole from forming before or during stellar evolution: at a period when all of its material would go down the hole and none be available for ejection?

Newton's laws. When the core collapses, all of that gravitational potential energy is released. It can't all just "fall down the hole". Now remember, that energy is ALL being released within the center of the star, and it is going to be imparted to the surrounding mantle.

Now think about this: the thermal heat of the star, prior to core collapse, was enough to support the mantle. It wasn't falling into the core, except perhaps slowly. In a few tens of milliseconds, that energy density is exceeded by tens of orders of magnitude, and you expect the mantle to fall inwards?

That's not to say that supermassive black holes didn't form in this period. They did. There are trillions of galaxies in our Hubble volume, and many contain million-solar-mass black holes at their cores. So there might be a trillion of those within causal reach. Wow!

We still would assume that the time, heat and pressure to go from first fusion (H + H and H - D, etc) to second generation fusion ... up to the final layer is not enough to overcome the black hole limits of gravity and distance.

I didn't understand that.

[<1/1,000,000th%]

Hey!

This is starting to get interesting.

[Robert A Cook PE]

Yeah - I erred.

I was thinking ahead of the problem, and got my thoughts fluxed up.

Regardless of how much mass in present, until that mass is concentrated so the escape velocity is irrelevant during any period of the first generation star until after it collapses, after the supernova.

Assume a star 10x the mass of the sun is first generation: It condenses, begins fusion, then goes through a lifecycle until the inner core is creating iron. If it goes supernova, the mass remaining in the center will be (almost certainly) to be within the Schwarzschild radius and lost to future generations, but as Phys. pointed out, that core mass is about 1/10 the mass of the original dust.

The remaining 90% of the original mass is ejected, ready for recycling. An open question is how much of that 90% that is ejected is "heavy" elements, and how much is unreacted H and He.

[Calvin Locke]

John Dobson tells a story in reference to the Big Bang theory: A king goes to visit a faraway city. Upon arrival, he didn't get a one gun, let alone a twenty-one gun, salute. He chastises the mayor who says he has three very good reasons: "First," he says, "there are no guns. Nevermind reasons two and three."

[Dinsdale]

ML/NJ super genius...

[gonzo]

"...Many "generations" of massive stars, and several generations of intermediate mass stars, contributed to the formation of the Sun..."

That's as I recalled it, RadioAstronomer, and the timing seems correct.

First-Generation stars would have no planetoids, but would be the furnaces for the formation of heavier elements.

Their destruction about 8 to 9 billion years ago would then lead to the formation of new Second-Generation stars with some solids-junk possible.

Subsequent aging and destuction-reformation leads to Third-Generation stars about 4.6 billion years ago with lotsa possibilities of planetoids, and lotsa heavier elements.

I've spent the last 45 years as a Plastics Engineer, so all I can do is wonder about the possibilities. Thanks for the interesting input ............... FRegards

[RadioAstronomer]

The weak force is the force that induces beta decay via interaction with neutrinos. A star uses the weak force to "burn" (nuclear fusion). Three processes we observe are proton-to proton fusion, helium fusion, and the carbon cycle. Here is an example of proton-to-proton fusion, which is the process our own sun uses: (two protons fuse -> via neutrino interaction one of the protons transmutes to a neutron to form deuterium -> combines with another proton to form a helium nuclei -> two helium nuclei fuse releasing alpha particles and two protons). The weak force is also necessary for the formation of the elements above iron. Due to the curve of binding energy (iron has the most tightly bound nucleus), nuclear forces within a star cannot form any element above iron in the periodic table. So it is believed that all higher elements were formed in the vast energies of supernovae. In this explosion large fluxes of energetic neutrons are produced which produce the heavier elements by nuclei bombardment. This process could not take place without neutrino involvement and the weak force.

[RadioAstronomer]

:-)

[Robert A Cook PE]

Thank you.

[SunkenCiv]

Note: this topic is from 2007. Thanks Robert A Cook PE.

---

join or quit view topics view or post blog bookmark post new topic subscribe

---