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From: mink@cfa.UUCP (Doug Mink)
Newsgroups: net.space
Subject: Re: Tenth planet
Message-ID: <159@cfa.UUCP>
Date: Mon, 30-Dec-85 15:05:42 EST
Article-I.D.: cfa.159
Posted: Mon Dec 30 15:05:42 1985
Date-Received: Wed, 1-Jan-86 04:27:25 EST
References: <8512272010.AA02178@s1-b.arpa>
Organization: Harvard-Smithsonian Center for Astrophysics
Lines: 32

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As someone with a professional interest in the positions of the outer
planets (I predict occultations), I have followed recent searches for a
tenth planet with great interest.  In fact, positions of Uranus obtained
from observations of occultations of stars by its rings (star-planet to
about a milliarcsecond) have helped narrow down the search region for
the supposed Planet X.  Unhappily, the best solar system ephemeris I
have available, JPL's DE-125, produced for the Voyage Uranus encounter
(see there IS a net.space connection), still fails to match Neptune's
observed position.  As I've been trying to predict occultations by
Neptune's satellite, Triton, so its size can be determined before
Voyager encounters Neptune in 1989, I need Neptune positions better than
any current solar system models can produce.  If Planet X is found, I
hope it cleans up the orbits of the outer planets.

A sidelight on Pluto's discovery:  A few years ago a friend of mine with
an intimate knowledge of the Harvard College Observatory photographic
plate stacks enlisted me in a quest for prediscovery Pluto positions.
He checked plates from 1870 to 1910 because no positions in that period
had been published despite numerous plates of the proper part of the
sky.  It turns out that Pluto was fainter than the plates exposed for
the average patrol exposure duration could detect until 1920 or so, though
a couple of long exposure plates after 1910 showed it.  Since Pluto is so
faint that it could only be detected photographically, it's no surprise
that Percival Lowell didn't find it and that discovery took until 1931.

			-Doug Mink
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