Jeff Root wrote:
Rising-Star8471 asked:

Given the numbers from the previous posts, does anyone have
any idea what the mass of an unseen object would have to be
to cause the speed discrepincy?

The mass depends on its distance from Pioneer. A larger
mass would be farther away; a smaller one would be closer.
But the mass would have to be fairly small or it would
affect other bodies in the Solar System. It doesn't.
Also, since the effect on the spacecraft was constant for
more than a decade, the masses would have to be following
the spacecraft at a constant distance behind them. The
masses would have to be approximately in line between the
Earth and the spacecraft, a short distance behind them.
And since the Pioneers were slowing down, in order to
maintain a constant distance, the masses would have to
be slowing down, too.

-- Jeff, in Minneapolis

Then I would have to go with dust. It appears that they are both
traveling the plane of the eclipic, where as the voyagers are both far
above and far below the ecliptic. Its possible that the solar system
still has dust rings beyond the orbit of Neptune that are leftovers
from planetry development. We woulnt neccisarly notice from here
because this dust would have always there to us, We dont have a "dust
free: enviroment to compare the observations to. This would also
explain why it happened to both probes, and the following body of mass
theroy. The probe is still plowing through the dust. When its speed
stablizes, it will have gone through the other side.

Star