From: metares@well.sf.ca.us (Tom Van Flandern)
Newsgroups: sci.astro
Subject: Re: Progress with New Cosmologies (& discrete redshifts)
Date: 11 Oct 92 20:59:31 GMT
Organization: Whole Earth 'Lectronic Link


hayim@locus.com (Hayim Hendeles) writes:

> A while ago, you wrote an article about the possible existence of a 10th
> planet. If I recall correctly, your premise was based on the residuals of
> Neptune's orbit. To be more specific, it seems impossible to reconcile 19th
> century observations with 20th century observations of Neptune.
>
> However, in a recent article (in Time magazine), there was a statement that
> recent studies (by someone in Canada) make it extremely unlikely that there
> is a 10th planet - at least based on observed residuals.  I think the
> argument was based on the accuracy of 20th century observations, along with
> the fact that no perturbations have been detected in any of the spacecraft.
>
> Therefore, I am curious, if you have seen this study and if you agree with
> its conclusions.

     An excellent question, Hayim.  The skeptical opinions about the possible
existence of "Planet X" mostly derive from the work of Standish at JPL.  I do
not fully agree with his conclusions.

     Anderson (also at JPL) is often quoted as saying that no perturbations
attributable to an unknown planet have been seen in the data from several
spacecraft now beyond Neptune's orbit.  While true, this is a little like
saying there is no evidence for another planet in the stock exchange index.
Statistically, the odds are that all spacecraft are farther away from the
hypothetical Planet X than are Uranus and Neptune during part of their
orbits.  Also the spacecraft are constantly barraged by non-gravitational
forces.  Chief among these are attitude control to keep their antennae
pointed earthward.  These introduce constant small impulses to the spacecraft
motion which cannnot be modelled out accurately enough to look for small
accelerations due to distant bodies in the residuals.  Anderson's fuller
statement (seldom quoted) is that the spacecraft data is not up to the task
of shedding light on undiscovered planets.

     The "20th century observations" argument is also often cited from
Standish's work.  When only the more accurate 20th century data is analyzed,
the fits of computation to observation are pretty good, with no significant
discrepancies.  If the 19th century data is included, the unmodelled
residuals are modest in size but definitely significant.  So, the argument
goes, maybe we are just seeing systematic errors in the 19th century data.

     The problem with this argument is that, if we take the best-fitting
orbit from the 20th century data only, and extrapolate it back to the 19th
century, the run-offs are so severe (3-5 arc seconds in 50 years) that nobody
would suggest that it could be due to observational error.  As nearly as we
can tell, the 19th and 20th century orbits are really slightly different.

     The best evidence for this effect is in the Uranus data, not Neptune,
because Uranus (period 84 years) has made several revolutions, whereas
Neptune has yet to complete one revolution since discovery.  But even for
Neptune there is the anomaly of the Lalande pre-discovery observations in
1790.  Lalande cataloged many faint stars with a typical accuracy of +/- 3
arc seconds.  Two of those faint stars turned out to be Neptune.  But they
stand off from the best modern Neptune orbits by about 10 arc seconds.  This
is either a most unfortunate statistical fluke, or something has slightly
disturbed Neptune's orbit since 1790.

     Comets are poor monitors of the outer solar system because they
experience non-gravitational forces from solar radiation pressure and similar
effects.  Fortunately, these are confined to the comet's orbital plane.
There are six comets of more than one return which go out beyond Neptune. All
six of these also show small unmodelled discrepancies *perpendicular* to
their orbital planes, which shorter-period comets do not.  Again it appears
that these bodies are experiencing small accelerations in the outer solar
system which we do not yet know how to explain.

     I should also mention that Standish's latest results, reported at the
AAS Division on Dynamical Astronomy meeting in Chicago this past June,
suggest that when Neptune's mass is set to the new value determined by the
Voyager fly-by, the problems in the orbit of Uranus "seem to disappear".  But
at least three earlier investigators had already tried similar masses of
Neptune in their work, and still saw the unmodelled effects.  So the new
Standish result raises more questions than it answers.  Research is
continuing.  -|Tom|-

-- 
Tom Van Flandern / Washington, DC / metares@well.sf.ca.us
Meta Research was founded to foster research into ideas not otherwise
supported because they conflict with mainstream theories in Astronomy.
Newsgroups: sci.astro