Why heavy elements don't sink

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BDanielMayfield
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Why heavy elements don't sink

Post by BDanielMayfield » Sat Aug 31, 2019 12:03 am

In stars that is. I ask because stellar spectra show the atomic absorption and emission lines of both lightweight and heavy elements as well. The atoms that are causing these lines can't be from too deep in the star, or we wouldn't be able to detect them. So what holds the heavier elements up in the photospheres of stars?

I suspect that it is ionization, but is that all there is to it? Wouldn't a slightly ionized heavy atom still tend to sink?

Bruce
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neufer
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Re: Why heavy elements don't sink

Post by neufer » Sat Aug 31, 2019 2:43 am

BDanielMayfield wrote:
Sat Aug 31, 2019 12:03 am

In stars that is. I ask because stellar spectra show the atomic absorption and emission lines of both lightweight and heavy elements as well. The atoms that are causing these lines can't be from too deep in the star, or we wouldn't be able to detect them. So what holds the heavier elements up in the photospheres of stars?

I suspect that it is ionization, but is that all there is to it? Wouldn't a slightly ionized heavy atom still tend to sink?
In star radiative zones ionized (heavy) atoms will indeed be pushed out. (Ionized hydrogen & helium are just protons & alpha particles that are relatively poor at absorbing light.)

In star convective zones (which dominate the volume of all stars) atoms end up completely mixed.

In our own atmosphere, the heavy CO2 molecule is a well mixed (at ~400 ppm and rising) throughout the Troposphere, Stratosphere and Mesosphere thanks to convection.
Art Neuendorffer

BDanielMayfield
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Re: Why heavy elements don't sink

Post by BDanielMayfield » Sat Aug 31, 2019 3:00 am

Thanks Art. That well explains why even the heaviest elements are observed in stars' photospheres.
"Happy are the peaceable ... "