On 29 Nov 2007 at 13:43, DED wrote:
>
> Hence why I wrote:
"I make no guarantees of the veracity of this
> formula (or my math). I'm
just passing along the info." =)
>
> One question with regards to:
"when they start getting more massive
> than Jupiter they just compact
all the extra mass in the same
> volume... "
>
> How do we
know this? Is it with computer models?
Probably. But given that the same
sort of models also work quite well
for star sizes and are based on lab
experiments with small volumes of
very high pressure.
Basically, once
you reach a certain mass (around that of Jupiter),
the pressure at the core
is enough to causing degenerate matter to
form.
That is, the electron
shells of the atoms can no longer keep them as
far apart as in normal solids
and density shoots up.
That higher density at the core makes the body
smaller.
And they'll keep getting smaller as the mass goes up right until
the
point where fusion starts happening.
As I recall, brown dwarfs
have some deuterium fusion going on at the
core so they get a bit bigger or
at least not smaller.
Once the mass hits the point where protium (H1)
can fuse, you get a
large expansion as the body becomes a red dwarf
star.
Going from small gas giant on thru the largest stars is all pretty
much one set of formulas and models.
--
Leonard Erickson (aka
shadow)
shadow at shadowgard dot com