APOD: Simulation: Formation of the First Stars (2021 Jun 30)

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APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by APOD Robot » Wed Jun 30, 2021 4:05 am

Image Simulation: Formation of the First Stars

Explanation: How did the first stars form? To help find out, the SPHINX computer simulation of star formation in the very early universe was created, some results of which are shown in the featured video. Time since the Big Bang is shown in millions of years on the upper left. Even 100 million years after the Big Bang, matter was spread too uniformly across the cosmos for stars to be born. Besides background radiation, the universe was dark. Soon, slight matter clumps rich in hydrogen gas begin to coalesce into the first stars. In the time-lapse video, purple denotes gas, white denotes light, and gold shows radiation so energetic that it ionizes hydrogen, breaking it up into charged electrons and protons. The gold-colored regions also track the most massive stars that die with powerful supernovas. The inset circle highlights a central region that is becoming a galaxy. The simulation continues until the universe was about 550 million years old. To assess the accuracy of the SPHINX simulations and the assumptions that went into them, the results are not only being compared to current deep observations, but will also be compared with more direct observations of the early universe planned with NASA's pending James Webb Space Telescope.

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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by VictorBorun » Wed Jun 30, 2021 4:40 am

resembles the appearing of the frost patterns on a window. When a filament precipitates it precipitates real quick

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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by orin stepanek » Wed Jun 30, 2021 11:34 am

There's an awful lot to digest here! Stars blow up and make little strars; and little stars have lesser stars and on to------ :shock! Anyway all the videos were very interesting; but 3 repeats? The one about star sizes was most interesting!

21042210_264995290674140_8840525631411191808_n.jpg
Awe; poor kitty looks sad!
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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by RJN » Wed Jun 30, 2021 1:53 pm

A kind and knowledgable emailer has pointed out that Webb has two "b"s, not one. This has now been corrected on the main NASA APOD. We apologize for the oversight.
- RJN

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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by seeko » Wed Jun 30, 2021 3:45 pm

I love your site. This title of this days subject makes it sound like the star formation enigma is solved. Gas disperses in space and gravity is not powerful enough to bring enough hydrogen together to make a star. James Jeans put the numbers to it a hundred years ago. Sure stars stay collapsed but a raw gas in space will not start to pull together with gravity unless something besides gravity compresses it. I would love to see a real solution to this problem - maybe electrodynamics? How did the simulation get past this? Did they start with fully gathered gas?

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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by Chris Peterson » Wed Jun 30, 2021 4:34 pm

seeko wrote:
Wed Jun 30, 2021 3:45 pm
I love your site. This title of this days subject makes it sound like the star formation enigma is solved. Gas disperses in space and gravity is not powerful enough to bring enough hydrogen together to make a star. James Jeans put the numbers to it a hundred years ago. Sure stars stay collapsed but a raw gas in space will not start to pull together with gravity unless something besides gravity compresses it. I would love to see a real solution to this problem - maybe electrodynamics? How did the simulation get past this? Did they start with fully gathered gas?
Gravity is all you need to create collapsed regions, and once you have any stars, you have supernovas to further create density gradients. (Understanding the dynamics also requires considering dark matter, which wasn't known a century ago.)
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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by neufer » Wed Jun 30, 2021 5:09 pm

:|
Chris Peterson wrote:
Wed Jun 30, 2021 4:34 pm
seeko wrote:
Wed Jun 30, 2021 3:45 pm

This title of this days subject makes it sound like the star formation enigma is solved. Gas disperses in space and gravity is not powerful enough to bring enough hydrogen together to make a star. James Jeans put the numbers to it a hundred years ago. Sure stars stay collapsed but a raw gas in space will not start to pull together with gravity unless something besides gravity compresses it. I would love to see a real solution to this problem - maybe electrodynamics? How did the simulation get past this? Did they start with fully gathered gas?
Gravity is all you need to create collapsed regions, and once you have any stars, you have supernovas to further create density gradients. (Understanding the dynamics also requires considering dark matter, which wasn't known a century ago.)
  • Gravity plus cooling by radiation is all you need to create collapsed regions.
https://en.wikipedia.org/wiki/Jeans_instability wrote:
<<In stellar physics, the Jeans instability causes the collapse of interstellar gas clouds and subsequent star formation, named after James Jeans. It occurs when the internal gas pressure is not strong enough to prevent gravitational collapse of a region filled with matter. Jeans instability can also give rise to fragmentation in certain conditions. To derive the condition for fragmentation an adiabatic process is assumed in an ideal gas and also a polytropic equation of state is taken.

If the adiabatic index:
  • γ > 4/3, the critical Jeans mass increases with increasing density,
    while if γ < 4/3 the Jeans mass decreases with increasing density.

During gravitational collapse density always increases, thus in the second case the Jeans mass will decrease during collapse, allowing smaller overdense regions to collapse, leading to fragmentation of the giant molecular cloud. For an ideal monatomic gas, the adiabatic index is 5/3. However, in astrophysical objects this value is usually close to 1 (for example, in partially ionized gas at temperatures low compared to the ionization energy).

More generally, the process is not really adiabatic but involves cooling by radiation that is much faster than the contraction, so that the process can be modeled by an adiabatic index as low as 1 (which corresponds to the polytropic index of an isothermal gas). So the second case is the rule rather than an exception in stars. This is the reason why stars usually form in clusters.
Art Neuendorffer

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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by VictorBorun » Wed Jun 30, 2021 11:08 pm

neufer wrote:
Wed Jun 30, 2021 5:09 pm
  • Gravity plus cooling by radiation is all you need to create collapsed regions.
I think I miss something.
All there was before the earliest stars was atomic neutral H and He, and the dark matter (too warm to collapse into a cloud smaller than a galaxy), and relic neutrinos (ultrarelativistically fast and so never collapsing into a cloud).
Without some cooling radiation it's ɣ=5/3 > 4/3, so Jeans is against any star-forming precipitation.
Without any metallicity it's thin chance for a photon emitted by one hot ionized atom + electron to escape from the core of a 1 ly thick cloud and not get re-captured by a neutral atom of the same sort.

So what exactly are we looking at watching the posted simulation?

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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by XgeoX » Thu Jul 01, 2021 3:16 am

orin stepanek wrote:
Wed Jun 30, 2021 11:34 am
There's an awful lot to digest here! Stars blow up and make little strars; and little stars have lesser stars and on to------ :shock! Anyway all the videos were very interesting; but 3 repeats? The one about star sizes was most interesting!


21042210_264995290674140_8840525631411191808_n.jpg
Awe; poor kitty looks sad!
I love these kitty photos you post!

Eric

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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by alter-ego » Thu Jul 01, 2021 3:25 am

VictorBorun wrote:
Wed Jun 30, 2021 11:08 pm
neufer wrote:
Wed Jun 30, 2021 5:09 pm
  • Gravity plus cooling by radiation is all you need to create collapsed regions.
I think I miss something.
All there was before the earliest stars was atomic neutral H and He, and the dark matter (too warm to collapse into a cloud smaller than a galaxy), and relic neutrinos (ultrarelativistically fast and so never collapsing into a cloud).
Without some cooling radiation it's ɣ=5/3 > 4/3, so Jeans is against any star-forming precipitation.
Without any metallicity it's thin chance for a photon emitted by one hot ionized atom + electron to escape from the core of a 1 ly thick cloud and not get re-captured by a neutral atom of the same sort.

So what exactly are we looking at watching the posted simulation?
You're missing the detailed complexity of star formation. There are multiple cooling channels available in the early, metal-free universe, the models include cosmic expansion, and the big-bang left regions of varying temperatures and of course densities. I'm not surprised that the simplest star-formation stopper you've outlined is not complete and subsequently fails. It must or we wouldn't have stars :)
Formation of the first stars (2018) wrote:Altogether, first star formation is likely to start at a redshift z & 30 in rare high-sigma fluctuations,
then rapidly becomes possible in more and more halos, and reaches a peak rate at redshifts z ∼
20 − 15.
The information in this paper is far more detailed and of course is not assumption free. Today's simulation is meant to show the first stars forming after the Big Bang, and has it's own assumptions. The details behind the model are simply not fully understood (by us).
A pessimist is nothing more than an experienced optimist

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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by neufer » Thu Jul 01, 2021 3:29 am

VictorBorun wrote:
Wed Jun 30, 2021 11:08 pm
neufer wrote:
Wed Jun 30, 2021 5:09 pm
  • Gravity plus cooling by radiation is all you need to create collapsed regions.
All there was before the earliest stars was atomic neutral H and He, and the dark matter (too warm to collapse into a cloud smaller than a galaxy), and relic neutrinos (ultrarelativistically fast and so never collapsing into a cloud).

Without some cooling radiation it's ɣ=5/3 > 4/3, so Jeans is against any star-forming precipitation.

Without any metallicity it's thin chance for a photon emitted by one hot ionized atom + electron to escape from the core of a 1 ly thick cloud and not get re-captured by a neutral atom of the same sort.
  • All there was before the earliest stars was atomic neutral H, He, lithium and dark matter:
https://en.wikipedia.org/wiki/Lithium#Astronomical wrote:
<<According to modern cosmological theory, lithium—in both stable isotopes (lithium-6 and lithium-7)—was one of the three elements synthesized in the Big Bang. Though the amount of lithium generated in Big Bang nucleosynthesis is dependent upon the number of photons per baryon, for accepted values the lithium abundance can be calculated, and there is a "cosmological lithium discrepancy" in the universe: older stars seem to have less lithium than they should, and some younger stars have much more. The lack of lithium in older stars is apparently caused by the "mixing" of lithium into the interior of stars, where it is destroyed, while lithium is produced in younger stars.

Lithium is also found in brown dwarf substellar objects and certain anomalous orange stars. Because lithium is present in cooler, less-massive brown dwarfs, but is destroyed in hotter red dwarf stars, its presence in the stars' spectra can be used in the "lithium test" to differentiate the two, as both are smaller than the Sun. Certain orange stars can also contain a high concentration of lithium. Those orange stars found to have a higher than usual concentration of lithium (such as Centaurus X-4) orbit massive objects—neutron stars or black holes—whose gravity evidently pulls heavier lithium to the surface of a hydrogen-helium star, causing more lithium to be observed.>>
  • With such low initial metallicity large Population III stars were able to form:
https://en.wikipedia.org/wiki/Stellar_population#Population_III_stars wrote:
<<Population III stars are a hypothetical population of extremely massive, luminous and hot stars with virtually no metals, except possibly for intermixing ejecta from other nearby Population III supernovae. Such large stars may have been possible due to the lack of heavy elements and a much warmer interstellar medium from the Big Bang. Population III stars have not yet been observed directly. Indirect evidence for their existence has been found in a gravitationally lensed galaxy in a very distant part of the universe. Their existence may account for the fact that heavy elements – which could not have been created in the Big Bang – are observed in quasar emission spectra.They are also thought to be components of faint blue galaxies. These stars likely triggered the universe's period of reionization, a major phase transition of gases leading to the lack of opacity observed today. Observations of the galaxy UDFy-38135539 suggest it may have played a role in this reionization process. The European Southern Observatory discovered a bright pocket of early population stars in the very bright galaxy Cosmos Redshift 7 from the reionization period around 800 million years after the Big Bang. The rest of the galaxy has some later redder Population II stars. Some theories hold that there were two generations of Population III stars.>>
Art Neuendorffer

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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by orin stepanek » Thu Jul 01, 2021 11:26 am

XgeoX wrote:
Thu Jul 01, 2021 3:16 am
orin stepanek wrote:
Wed Jun 30, 2021 11:34 am
There's an awful lot to digest here! Stars blow up and make little strars; and little stars have lesser stars and on to------ :shock! Anyway all the videos were very interesting; but 3 repeats? The one about star sizes was most interesting!


21042210_264995290674140_8840525631411191808_n.jpg
Awe; poor kitty looks sad!
I love these kitty photos you post!

Eric
Thanks they are part of APOD's write=up! :)
"matter was spread too [uniformly] across the cosmos for stars to be born."
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Re: APOD: Simulation: Formation of the First Stars (2021 Jun 30)

Post by VictorBorun » Fri Jul 02, 2021 5:05 am

neufer wrote:
Thu Jul 01, 2021 3:29 am
  • All there was before the earliest stars was atomic neutral H, He, lithium and dark matter:
I think I got it.
As tiny as it was,

Lithium-7 and lithium-6 produced in the Big Bang are on the order of: 7Li to be 10−9 of all primordial nuclides; and 6Li around 10−13.

Li fraction gave early protostellar clouds some powerful glow from deep within those mostly H+He gas.
Every Li atom was an important radiator because it easily got thermal energy from collisions with H or He atoms and ions and free electons and then sent it far away as a photon of a wavelength of light-year penetrating capacity.
There were other Li atoms in the way but not many. So that photon might zigzag a few times before finally managing to escape the hot collapsing cloud.
If the dense H+He were radiating from 10,000 kilometers deep while Li did it from 10 ly deep, then Li shone 10 times as bright as all the H+He.