Sun <==> Alpha Centauri gravity interactions

Some texts (notably one or two books I vaguely recall of Patrick
Moore's) often show projections of *brightest* and *closest* stars in
the several thousand years before and after the present time. I
distinctly recall that Barnard's star is one that will become the
closest star to the Sun in so many thousands of years from now at
around 3.5(?) odd light years and then it will start receding away
from us again after that time.

Firstly, how does one go about making such future positional guesses
and secondly, how long has Alpha Centauri been in close proximity to
the Sun? Is there any projections as to how long Alpha Centauri will
stay this close?

Could it be that Alpha Centauri (A+B+C) and the Sun are
gravitationally *locked* together and share a common proper motion
around the galaxy? I know we observe distinct radial velocity and
proper motions that Alpha Centauri has relative to the Sun, but they
are based on short term measurements in the current era... and I don't
expect you can simply *extrapolate* forwards/backwards in time simply
on the basis of their present values... or can you?

According to "Solstation" (my number one favourite site for local star
system research!):-
http://www.solstation.com/stars/alp-cent3.htm

the next nearest large star system to have any *significant*
interaction with both the Sun and Alpha Centauri(A+B+C) is Sirius
(A+B) - which is quite far removed at 8.6 LY away from the Sun and 9.5
LY away from from Alpa Cen.

This means the Sun and Alpha Centauri system are relatively isolated
in space, where it is conceivable that bodies orbiting far out around
each system are gravitationally perturbed in the manner in which I
illustrate he-

http://uk.geocities.com/aa_spaceagen....html#midrange

Its important I think to study our nearest triple star system in
greater depth (if only it rose above my horizon... but then I can't do
a lot with my tiny 8-inch Newtonian!). How much Hubble or other
space/ground-based telescope time is devoted to Alpha Centauri,
compared to all other stellar astronomy, I wonder...

cheers
Abdul Ahad