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What molecules can form in a star?
Is there stellar chemistry that happens along side of nuclear fusion?
When elements are created do they tend to bond to themselves? How else could you get for instance something like gold to always be found with itself as a rule. This togtherness of likes looks like the norm behind stellar chemistry and what eventually becomes the planets. What molecules start at the stars? Mitchell Raemsch |
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What molecules can form in a star?
On 14/09/2011 12:56 AM, jon car wrote:
[irrelevant groups dropped] Is there stellar chemistry that happens along side of nuclear fusion? In stars with cool enough outer layers, molecules are detected in those layers via spectroscopy. When elements are created do they tend to bond to themselves? No. It's hot gases in the outer layers of cool stars, and ionized plasma everywhere else in stars as a general rule. How else could you get for instance something like gold to always be found with itself as a rule. Crystallization in a planet that's cooling and solidifying, or a magma intrusion that's doing so. Like tends to clump with like, because if an atom or molecule of species A tries to add itself to a growing crystal of species B (or a growing hodgepodge) there will be more lattice defects, and so higher energy, than if it tries to add itself to a growing crystal of species A. The thermodynamically favored behavior is thus for similar minerals to precipitate out into monospecific crystals. Gold, in particular, tends to form clumps of native gold metal. Minerals are also often found in association with particular other minerals, generally because they have similar freezing points under the pressures where crystallization tends to take place and their constituent molecules tend to occur together in magmas. This togtherness of likes looks like the norm behind stellar chemistry and what eventually becomes the planets. Actually, as outlined above the separation of minerals and grouping of like with like is mainly a process that occurs inside forming planets (and in vulcanism). Though there is one crude separation that happens earlier, in a proplyd when the central star ignites. The solar wind tends to blow atoms outwards, and the lighter the atom the farther it gets blown and from farther out from the star. So, bodies made primarily of ice, hydrogen, ammonia, methane, and other light molecules of light elements form in the outer solar system (hot Jupiters are thought to spiral inwards later due to drag from accretion; what stops a Jupiter from sweeping all of the proplyd inwards of its nucleation point and plunging into the star is, 1. some, like our own Jupiter, run into a clear area usually created by their own gravity making a band of orbits in the proplyd unstable earlier and halt, and 2. the ones that sweep up most of the proplyd feel tidal forces from the star when they get close and this can lock them into a stable, resonant orbit; or the inner edge of the proplyd is reached, inward of which the stellar wind blew away even the heaviest elements). Rocky bodies are found farther in. Metal-dominated bodies are either rocky ones that had enough heat of accretion to melt, so the denser materials settled into the core, and then had their outer layers blasted off, or formed very close to the star. (Mercury is probably a little of both.) And as noted denser materials settle to the cores of planets that get hot enough during accretion to melt at least partially. Volcanic worlds have some subsequent mixing, and impacts can also deliver dense materials to near the surface (some of Earth's bigger nickel mines are actually tunneling into asteroids that buried themselves in its crust eons ago); vulcanism can also erupt light gasses to the surface from the interior, replenishing an atmosphere of lighter elements even at distances from the sun and for small enough worlds that the air slowly leaks away into space. There is some debate about how long water locked up in Earth's interior will replace what Earth loses to space, with the Earth maybe drying out in 500 million years and maybe not until 2 billion years from now -- a difference by a factor of four, so not a very precise knowledge as of yet! What molecules start at the stars? A few light ones. I'm not sure exactly which. Try Wikipedia or Google for anything you have more questions about. |
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What molecules can form in a star?
On 14/09/2011 06:42, Poutnik wrote:
In article2899c2dd-7c4a-41fb-8fe7-b9831b4d2a04 @g14g2000pre.googlegroups.com, says... Is there stellar chemistry that happens along side of nuclear fusion? When elements are created do they tend to bond to themselves? Not inside a star it is way too energetic for any chemistry (a few eV) to occur in the vicinity of a fusion reaction ( MeV). How else could you get for instance something like gold to always be found with itself as a rule. This togtherness of likes looks like the norm behind stellar chemistry and what eventually becomes the planets. Gold only gets sorted when you have low enough temperatures for diffusion limited reactions and/or gravitational sorting. It is a good rule of thumb that only very young and very old rocks are gold bearing as mineable ore. Middle aged rocks are gold poor. Uranium is much more fickle and is present in most crustal rocks at around 2ppm (relatively common) but seldom found as mineable grade ore. What molecules start at the stars? Mitchell Raemsch I am not sure if any bond can with stand combination of hot surface temperature and breaking high energy radiation. of stars in middle of their age. Depends mostly on the surface temperature and strength of the chemical bond. You can see absorption lines for very strongly bonded molecules like CN in the atmosphere of stars with surface temperatures of 4000K or less (and that is still pretty hot). For read giants it could be possible, like H2, CO, NO TiO is one of the more commonly observed absorption lines in red giants. Other refractory oxides may also be present. http://outreach.atnf.csiro.au/educat...ral_class.html Has a table part way down in the spectral class summary section. Regards, Martin Brown |
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What molecules can form in a star?
On Sep 14, 3:38*am, Martin Brown
wrote: On 14/09/2011 06:42, Poutnik wrote: In article2899c2dd-7c4a-41fb-8fe7-b9831b4d2a04 @g14g2000pre.googlegroups.com, says... Is there stellar chemistry that happens along side of nuclear fusion? When elements are created do they tend to bond to themselves? Not inside a star it is way too energetic for any chemistry (a few eV) to occur in the vicinity of a fusion reaction ( MeV). How else could you get for instance something like gold to always be found with itself as a rule. This togtherness of likes looks like the norm behind stellar chemistry and what eventually becomes the planets. Gold only gets sorted when you have low enough temperatures for diffusion limited reactions and/or gravitational sorting. It is a good rule of thumb that only very young and very old rocks are gold bearing as mineable ore. Middle aged rocks are gold poor. Uranium is much more fickle and is present in most crustal rocks at around 2ppm (relatively common) but seldom found as mineable grade ore. What molecules start at the stars? Mitchell Raemsch I am not sure if any bond can with stand combination of hot surface temperature and breaking high energy radiation. of stars in middle of their age. Depends mostly on the surface temperature and strength of the chemical bond. You can see absorption lines for very strongly bonded molecules like CN in the atmosphere of stars with surface temperatures of 4000K or less (and that is still pretty hot). For read giants it could be possible, like H2, CO, NO TiO is one of the more commonly observed absorption lines in red giants. Other refractory oxides may also be present. http://outreach.atnf.csiro.au/educat...sics/spectral_... Has a table part way down in the spectral class summary section. Regards, Martin Brown Sun is to hot to have molecules. It has the 4th state of matter called plasma. In plasma we see atoms and molecules torn apart leaving positive charged atomic nuclei,and electrons. TreBert |
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What molecules can form in a star?
bert wrote:
On Sep 14, 3:38 am, Martin Brown wrote: On 14/09/2011 06:42, Poutnik wrote: In article2899c2dd-7c4a-41fb-8fe7-b9831b4d2a04 @g14g2000pre.googlegroups.com, says... Is there stellar chemistry that happens along side of nuclear fusion? When elements are created do they tend to bond to themselves? Not inside a star it is way too energetic for any chemistry (a few eV) to occur in the vicinity of a fusion reaction ( MeV). How else could you get for instance something like gold to always be found with itself as a rule. This togtherness of likes looks like the norm behind stellar chemistry and what eventually becomes the planets. Gold only gets sorted when you have low enough temperatures for diffusion limited reactions and/or gravitational sorting. It is a good rule of thumb that only very young and very old rocks are gold bearing as mineable ore. Middle aged rocks are gold poor. Uranium is much more fickle and is present in most crustal rocks at around 2ppm (relatively common) but seldom found as mineable grade ore. What molecules start at the stars? Mitchell Raemsch I am not sure if any bond can with stand combination of hot surface temperature and breaking high energy radiation. of stars in middle of their age. Depends mostly on the surface temperature and strength of the chemical bond. You can see absorption lines for very strongly bonded molecules like CN in the atmosphere of stars with surface temperatures of 4000K or less (and that is still pretty hot). For read giants it could be possible, like H2, CO, NO TiO is one of the more commonly observed absorption lines in red giants. Other refractory oxides may also be present. http://outreach.atnf.csiro.au/educat...sics/spectral_... Has a table part way down in the spectral class summary section. Regards, Martin Brown Sun is to hot to have molecules. It has the 4th state of matter called plasma. In plasma we see atoms and molecules torn apart leaving positive charged atomic nuclei,and electrons. TreBert The Sun's spectrum shows that there are some diatomic molecules like CN and CH in the photosphere. -- Mike Dworetsky (Remove pants sp*mbl*ck to reply) |
#7
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What molecules can form in a star?
On 9/13/11 9/13/11 - 11:56 PM, jon car wrote:
Is there stellar chemistry that happens along side of nuclear fusion? Yes. But it is chemistry appropriate for the enormous temperatures and high densities, and thus varies throughout the star. It is also VERY different from what we observe on earth, due to those very different conditions. Few molecules form for very long ( femtoseconds), because the temperature and density are high enough throughout most of the star to immediately disassociate them. Near the surface the density can be low enough that molecules remain for measurable durations. When elements are created do they tend to bond to themselves? Yes, for a few femtoseconds, then other atoms bump into them with sufficient energy to disassociate any molecules. This togtherness of likes looks like the norm behind stellar chemistry and what eventually becomes the planets. The planets are VERY MUCH cooler than the stars, and this STRONGLY affects the longevity of chemical bonds. What molecules start at the stars? Everything except hydrogen and helium (which does not form molecules) and tiny amounts of Be and Li were formed in stars. At least in our best models today. Tom Roberts |
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