Here’s an interesting take on the Pioneer effect–the mysterious deceleration that seems to be afflicting Pioneer 10 and 11 as they head out of the Solar System.
If the effect is real, it ought to influence the orbits of the outer planets. Pluto, in particular, ought top feel this force if it’s out there. In the last few years, a few astronomers have calculated what sort of influence the Pioneer effect should have on Pluto, concluding that it should produce significant periodic effects. The fact that we don’t see these effects means we can rule out the Pioneer effect as a phenomenon affecting the outer planets, they say. And that means it probably isn’t a fundamental effect but some kind of artifact.
But now it sees that it’s too early to be making these kinds of assertions. Gary Page from George Mason University in Virginia and a couple of pals say the calculations are less than convincing. They point out that our knowledge of Pluto’s orbit is based entirely on optical observations and so are far less well characterised than the nearer planets.
In fact, so poor is our knowledge of Pluto’s orbit that it is impossible to say whether it is being pulled by a Pioneer-like force or not.
Page and pals say:
“Of course, this does not mean that the Pioneer effect exists. It does mean that we cannot deny the existence of the Pioneer
effect on the basis of motions of the Pluto as currently known.”
Ref: arxiv.org/abs/0905.0030: How Well Do We Know The Orbits Of The Outer Planets?