[meteorite-list] Pluto's Fate to be Decided by 'Scientific andSimp

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed Aug 16 00:07:28 2006
Message-ID: <003501c6c0d4$c8d611b0$6a4fe146_at_ATARIENGINE>

Hi,

    There's a long history of hunting for a "large" planet
beyond Pluto, Pickering proposed one, Lyttleton, and
others besides Lowell. They were all looking for a small
gas giant, a sub-Uranus sized dim gas giant (which is
what Pluto was presumed to be for the first 30 years
after its discovery).
    The search was a mathematical one, working on
"residuals" -- those "irregularities in the orbits of Uranus
and Neptune" -- but it depends on mass assumptions.
    So the accurate determination of Neptune's mass
rules out "large" bodies in the gas giant sense, but a
"Plutonian" planet the size of Mars, with a density of
2.0 would have a mass of 0.04 to 0.05 of that of the
Earth. At a distance of 150 to 200 AU, its gravitational
influence on Neptune and Uranus would be less than
the less-massive but much nearer Pluto, and Pluto's
perceptible (in orbit timing) influence is very, very
small.
    In terms of "gravitational" detection, forget it.
    A Mercury-sized body at such distances would be
even more undetectable; it would mass 0.008 to 0.010
Earth mass, pretty puny. At a distance of 150 to
200 AU, it would gravitationally "invisible" and
damn near optically invisible as well.
    Some of the "TBO" planets have respectable
albedoes. Pluto can be as bright as 0.50 to 0.65, but
others are quite dim, < 0.10. Pluto was probably
discovered first because of a) luck and b) it was
the brightest of the "Plutonian" planets.
    And, hey! I was being cautious in talking about
Mars-size and Mercury-size Plutonians. How about
a Venus/Earth sized body, density 1.8, mass 0.28
Earths, at 242 AU. Its orbital period would be close
to 4000 years (3720 years if eccentricity was ~0.0,
which it wouldn't be), and an albedo of 0.07?
    It would be very dim, and as for gravitational
detection, it would hardly have moved in the
century we have (crude) data for the other planets:
it would be nestled well inside the error bars...
And remember 2003EL61 and 2005FY9 -- both
are almost as bright as Pluto; they can be imaged
with a 12" scope ONCE THEIR LOCATIONS
ARE KNOWN, but otherwise, they hide out very
well. Finding them with a 12" scope would take
you a century or two...
    Loan me such a Venus/Earth-sized plutonian,
and I'll stash it at 242 AU somewhere in the K-belt,
and we'll see just how it takes to find it! But watch
me; I'm tricky. I might give it a high inclination orbit.


Sterling K. Webb
----------------------------------------------------------
----- Original Message -----
From: "Ron Baalke" <baalke_at_zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com>
Sent: Tuesday, August 15, 2006 11:33 AM
Subject: Re: [meteorite-list] Pluto's Fate to be Decided by 'Scientific
andSimp


>>
>> Bigger than Pluto? At greater AUs'out?
>>
>> This could explain the comets that come out of the blue appear once and
>> never return.
>>
>> Did not astronomers think that it was interstellar perturbations that
>> "jarred" the K-belt?
>>
>> A large "planet(s)" out there would have much more effect than stars
>> light years away.
>>
>
> We would have seen evidence of a large planet by now, which we've haven't.
> Analysis by Myles Standish at JPL indicates that a large planet out
> beyond Neptune does not exist. Some astronomers have been searching
> for a Planet X based on what appeared to be irregularities
> in the orbits of Uranus and Neptune. However, when the extremely accurate
> measurements of the mass of Neptune made by the Voyager 2 flyby in 1989
> are inserted in the equations, these irregularities vanish. Prior to the
> Voyager 2 flyby, the mass number used for Neptune was off by five-tenths
> of 1 percent. When the new value for Neptune's mass is factored into the
> equations, the orbits of the outer planets are shown to be moving as exp
> ected, going all the way back to the early 1800's. The results of
> Standish's
> analysis are published in the May 1993 issue of The Astronomical Journal
>
> Ron Baalke
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>
Received on Tue 15 Aug 2006 09:39:15 PM PDT