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Hlafordlaes
2014-Jul-08, 03:00 PM
I was running through some wiki entries on nucleosynthesis and ended up with a couple of questions I could not get answered from the readings.

1. What process sorts a dust and gas cloud into the stellar core and surrounding planets in such a way as to produce different metallicities, if indeed any such process takes place? That is, would not roughly the same mix of elements (primordial gas and Type II-III stellar remnants) that forms the planets also form the Sun, such that we would find some trace elements heavier than iron at the core?

I could not find spectroscopy data to indicate there are any sort of trace heavy elements in the Sun, so either there are none, or I found incomplete data. So, did no trace elements fall into the Sun (seems unlikely), or are the amounts so small that they are undetectable, or is there some other process inhibiting the presence of these elements in a Type I?

Post-solar formation, I can see the stellar wind pushing cosmic dust particles outward from then on, but what impedes their forming part of the Sun initially? Could there be, say, a few tons of heavy elements at the Sun's core, inside the iron core, yet undetectable? (I ask for curiosity's sake alone; not a woo proposal.)

2. Is there any process that favors rocky planets close to a star, and gas giants further out, or is the distribution of planetary bodies more a function of arbitrary systemic gravitic interactions that determine final orbits? I realize we've detected many giants in tight stellar orbits elsewhere, and an increasing variety of systems in general, but I have no idea if theory indicates any kind of preferential location for planet types. (Again, I would naively expect heavier elements closer in, and dust/gas pushed further out by the stellar wind during planet formation.)

Thanks for any clarifications you can provide.

ngc3314
2014-Jul-08, 04:48 PM
I could not find spectroscopy data to indicate there are any sort of trace heavy elements in the Sun, so either there are none, or I found incomplete data. So, did no trace elements fall into the Sun (seems unlikely), or are the amounts so small that they are undetectable, or is there some other process inhibiting the presence of these elements in a Type I?

The Sun has spectroscopically measured heavy elements up to thorium (the only uranium spectra lines that might be detected are at wavelengths wiped out by carbon - U has been measured only in a few carbon-deficient stars). An accounting is in, for example this meeting review (http://arxiv.org/pdf/1010.2746v1.pdf).



2. Is there any process that favors rocky planets close to a star, and gas giants further out, or is the distribution of planetary bodies more a function of arbitrary systemic gravitic interactions that determine final orbits? I realize we've detected many giants in tight stellar orbits elsewhere, and an increasing variety of systems in general, but I have no idea if theory indicates any kind of preferential location for planet types. (Again, I would naively expect heavier elements closer in, and dust/gas pushed further out by the stellar wind during planet formation.)


Very broadly, temperature and escape velocity. The major classes of materials in the planetary system - metals, rock, ices, and H/He - condense from hot gaseous phases at successively lower temperatures (H/He not at all at low pressures), so they would be expected to solidify in that order of distance from the young Sun. Beyond that, when a growing protoplanet becomes massive enough to retain H/He at its surroundings' temperature, it gets a huge advantage over small ones, having access to about 99% of the surrounding mass. A far as I know, all models for producing hot Jupiters involve radial migration after the planets reach these masses.

Hlafordlaes
2014-Jul-08, 05:23 PM
The Sun has spectroscopically measured heavy elements up to thorium (the only uranium spectra lines that might be detected are at wavelengths wiped out by carbon - U has been measured only in a few carbon-deficient stars). An accounting is in, for example this meeting review (http://arxiv.org/pdf/1010.2746v1.pdf).

Very broadly, temperature and escape velocity. The major classes of materials in the planetary system - metals, rock, ices, and H/He - condense from hot gaseous phases at successively lower temperatures (H/He not at all at low pressures), so they would be expected to solidify in that order of distance from the young Sun. Beyond that, when a growing protoplanet becomes massive enough to retain H/He at its surroundings' temperature, it gets a huge advantage over small ones, having access to about 99% of the surrounding mass. A far as I know, all models for producing hot Jupiters involve radial migration after the planets reach these masses.

Thanks for all that. Interesting. I'll now wade through the linked paper a bit.