In article ,
Abdul Ahad wrote:
When Pioneer 10 eventually passes Aldebaran - projected to be in
around 2 million years time (!), do we know how "close" the flyby is
likely to be...not that we'd be around to witness such an event of
course. How accurate are the [interstellar] dynamical considerations
in projecting these trajectories I wonder?

Last I heard, the biggest uncertainty was simply poor knowledge of the
relative velocities of the stars (which are moving much faster than
Pioneer itself).

I mean the gravity/mass
estimates of stars and their perturbing influences in the vicinity of
a spacecraft's trajectory projected across such vast interstellar
volumes of space... on journeys over millions of years ... surely adds
up to major inaccuracies in the computations?

Not really, not unless you assume undiscovered dim stars near the path
(which is a possibility -- sky-survey missions like Hipparcos have had
limited sensitivity). Everything else is just too far away to make a
big difference on that time scale.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |