Re: poly: Carbon; Learning algorithms?

At 12:02 PM 1/14/98 MST, Richard Schroeppel wrote:
>
>If we plunk the Earth in to the sun, and pretend it's pure carbon (haha)
>what happens? ... But would adding .0003%
>solar mass of a carbon catalyst affect the burn rate significantly?

About half of the energy of the sun is generetd by CNOF-catalyzed fusion,
and the sun is 1% CNOF, so increasing its CNOF content by .03% would
increase its burn rate by .015%.

>If so, then the second and third generation stars should burn a lot faster;

Remember that we only care about CNOF catalysis in stars of solar mass or
bigger. All such stars of the first or second generation burned out long
ago, even with their slower rate of uncatalyzed fusion. The Sun is third
generation.

>and a star's burn rate might be affected by wandering through a carbon cloud;

All interstellar clouds have about the same composition. They're all
swirled together up there.

It's unfortunate; I remember when I was a kid reading about astronauts
marooned on a planet with different elemental abundances. After a while
they started to suffer from unheard-of mineral deficiencies, like chlorine
deficiency. They had to set up a smelter to get tiny traces of chlorine
out of the rocks, which were mostly scandium flouride. Or whatever; I
forget the exact elements. Anyway, it won't happen that way, alas.

>and evolution studies should think about the solar wind carrying off heavy
>elements selectively (or vice versa);

They do. It only matters for white dwarfs, because the gravity of more
normal stars is not strong enough to separate elements by density.

>and mass:luminosity would be a
>mediocre predictor of lifetime without knowing carbon content.

All current big stars condensed fairly recently out of the standard uniform
interstellar cloud, and hence have pretty much the same carbon content.
Small stars that survive from the earlier generations don't use CNOF
catalysis and so don't care about carbon content. So, the mass &
luminosity is a good predictor of lifetime.

--CarlF
Received on Mon Jan 19 19:00:49 1998