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From: Lynn.es@XEROX.ARPA
Newsgroups: net.space
Subject: Re: Tenth planet
Message-ID: <851224-112816-1291@Xerox>
Date: Tue, 24-Dec-85 14:29:19 EST
Article-I.D.: Xerox.851224-112816-1291
Posted: Tue Dec 24 14:29:19 1985
Date-Received: Wed, 25-Dec-85 23:20:13 EST
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Soon after Tombaugh found Pluto, it was fairly evident to him that he
had not found the perturbation cause.  During the 30's and 40's he
completed a photographic survey of a wide band about the ecliptic
without finding anything.  So either the wandering ways of Uranus and
Neptune are 1) errors in measurement, 2) caused by another effect (dust
disks, Oort cloud, whatever), 3) caused by a planet that was very far
from the ecliptic when Tombaugh photographed, or 4) caused by a planet
too dim to show up in Tombaugh's survey.  Pluto runs about magnitude 13
to 14, and if I remember right, Tombaugh's survey should have found
anything brighter than 16 or so.  You can check the details by reading
Tombaugh's recent book, titled something like "Out of the Darkness".

I have heard of a few astronomers (Charles Kowal at Palomar is the only
name I can remember right now) interested in the tenth planet, but no
results.  It seems the data are inconsistent, so they have to decide
whose observations to consider too unreliable to use.  Also, the effect
is only a little larger than the expected errors of measurement.  

One idea is to look for the planet in the IRAS satellite IR sky survey.
It is said to be far more sensitive to a planet-type object than
Tombaugh's survey.  All you have to do is weed out the several hundred
thousand objects found by IRAS that are not planets!  Even among moving
objects in the IRAS data, thousands of asteroids clutter up the search.
There are also some pessimists that claim we will eventually find the
tenth planet in the 1% of the sky that IRAS missed photographing.

/Don Lynn