> By the way, where does the electron come from? I was under the
> impression that the Sun, at least the part that is fusing, is
> very positively ionic. If this is so, then where are the
> electrons coming from? Is there another form of mass decay
> taking place? Or is this simply one of the means by which the
> Sun regulates its rate of fusion? Or am I simply misinformed?
> Jerry Williams ([email removed])
Don't forget that there are *two* decay routes which can change a proton
into a neutron: beta absorption (proton plus electron -> neutron plus
neutrino) and inverse-beta decay (proton -> neutron plus positron plus
neutrino); I believe the latter is much more common, because the proton is
not at all dependent on "finding" an appropriate electron which allows the
decay. Also, being a nuclear physicist, I should point out that a free
proton will not decay to a neutron in any case (not energetically favor-
able). However, in a nucleus containing a large number of protons (relative
to the number of neutrons) *will* undergo such a decay.
So, look at a collapsing interstellar gas cloud composed entirely of
hydrogen-1. As it collapses, grav potential energy becomes kinetic energy--
the gas heats up. Eventually, the gas reaches a temperature (or energy)
high enough to let the protons (which make up the hydrogen-1 nuclei)
overcome their electrostatic repulsion. Somewhere in the cloud, two
protons come close enough to experience the strong nuclear force. This is not
sufficient, however; the di-proton is energetically unfavorable and will soon
fall apart. But, before they fall apart, it is possible for the weak nuclear
force to cause an inverse-beta dacey of one of the protons--bingo! We have a
deuteron. At this point things get more complex, but we see the basic
procedure:
p + p + 0.5 MeV --> He-2* --> d
\ / | | |
| | | +--> deuteron
| | +------------> excited di-proton (unstable)
| +--------------------------> coulomb barrier (rough calc.)
+----------------------------------> two hydrogen nuclei (protons)
The number 0.5 MeV may be dead wrong; I used a guess based on about
thirty seconds worth of thought.
JARRIO,MARTIN MICHAEL | Everyone's out to get me, and frankly,
Demented Physicist | its starting to make me paraniod.
Georgia Institute of Technology |
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