[meteorite-list] Three New 'Trojan' Asteroids Found Sharing Neptune's Orbit

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sat Jun 17 15:40:58 2006
Message-ID: <001801c69245$f0eeac10$67394842_at_ATARIENGINE>

Hi, Larry, List,

    It is a little puzzling, but I assume that what
they're describing is the discovery of an asteroid
in an orbit identical to Neptune's but tilted 25 deg
to Neptune's and having an asteroid in the Trojan
position to where Neptune would be if Neptune
were in that orbit instead of the orbit that Neptune
actually is in, if a woodchuck could chuck wood....

    What's unclear to me is why an asteroid would
settle down in the Trojan position of an asteroid
in an orbit identical to Neptune's but tilted 25 deg
to Neptune's and having that asteroid in the Trojan
position to where Neptune would be if Neptune
were in that orbit instead of the orbit that Neptune
actually is in, if Neptune isn't actually IN that orbit,
providing the gravitational situation which makes
the Trojan position stable?

    I spoze that Neptune's gravitational influence
out there in them thar wide open spaces is great enough
to provide stability even to an inclined co-orbit. My
first thought was that maybe Neptune's influence on
an inclined orbit was only strong enough to sustain
Trojans in a zone near to Neptune's orbit, but then
I realized that all these inclined orbits would have
nodes with the orbit of Neptune, so that the Neptune
Trojans in inclined orbits would pass through Neptune's
orbit at two points, the nodes.

    Since, as Larry pointed out, the Trojans of a major
planet like Jupiter are actually a "cloud" of asteroids.
He says, "...they can be inclined to the orbit of Jupiter
slightly closer or further from the Sun, or slightly in front
of or behind the 60 degree point." To indulge is Science's
favorite sport, the Quibblefest, only the ones slightly
"above" and "below" the major planet's orbit have a
different inclination; the examples cited vary in axis
and time of perihelion passage, but of course the vast
majority of those Trojans vary in all three parameters.
Such a "cloud" should be roughly ellipsoidal stretched
to banana shaped and lying within the boundary wherein
the major planet's gravitational influence greatly exceeds
that of all other bodies, which in the case of major
planets in the wide open spaces of the outer system is
probably a pretty big ranch.

    An object in ANY inclined orbit that was in the
"Neptune" position would smack right into Neptune,
so we can expect this point and all the orbital territory
even near to it to be completely empty by now! And,
unless the pictures in my head are all wrong (it could
happen), the "Neptune" Trojan point should also pass
through Neptune's "Neptune" Trojan point!

    This raises the prospect of what I can only call an
example of really heavy cross-town traffic as the asteroids
of the inclined Trojans slice through the "regular" Neptune
Trojans at the inclined angle. This is not as exciting and
video-game-like as it sounds, since the orbital speed out
in them thar wide open spaces is only 5.43 km/sec mph.
Still, it must get interesting at times... Particularly since
all the differently inclined orbits' Trojan points should
be making that passage at pretty much the same time!
Every 165 years...

    This raises some interesting considerations. How could
such a population of inclined Trojans arise?. Method One:
start with asteroids everywhere and stir and churn for 4 billion
years until only the stable ones are left. Fly in Ointment: four
billion years isn't long enough. Method Two is more intriguing...
Suppose that there are largish objects (500 to 2000 km) in
inclined Neptune-like orbits (as well as in the Neptune orbit).
Repeated low-speed collisions would create Trojan "clouds"
of smaller objects.

    Method Two B is for a still larger object 1000 to 3000
km) to be lurking in an high-inclination Neptune co-orbit
which would periodically deflect Neptune Trojans into inclined
orbits (not the same as the intruder). I hear the astronomers
grimacing; it would eventually hit Neptune. Nah! Every
close pass would alter its orbit, making eventual collision
very improbable. Or, maybe it's impossible. Hard to tell
about dynamic arguments without working it out, but odd
synchronizations abound...

    But... But... Surely we would have found it! Hey! Not
of you don't ever point the telescope out-of-plane... Galileo
found Neptune with the World's Largest Astronomical
Telescope -- 30 mm objective with quality we would
consider suitable for a child's toy, or maybe not even that.
    *Galileo first observed Neptune on December 28, 1612
It was stationary because it had just turned retrograde
that very day; he thought it was a star and charted it as
such.

    As the "more asteroids than in the Main Belt," they are
apparently talking about asteroids 60 km diameter and
larger when they say, "Neptune Trojans may outnumber
the tens of thousands of asteroids in the main asteroid belt."
The Main Belt, of course has far more asteroids than tens
of thousands! Although it is not clear to me why there
would not be numerous small asteroids in this Neptune
Trojan crowd also.

    Ron's newer post of
http://www.newscientistspace.com/article/dn9340-new-trojan-asteroid-hints-at-huge-neptunian-cloud.html
contains more details. The "freeze-in" theory they propose
would require there to be a minimum of 100,000,000
big asteroids to be Neptune co-orbits prior to the freeze,
so they are nothing if not very generous with their asteroids!
(Actually it might require a billion or more, but I don't
want to quibble...) ALL the theories require a big bag
of asteroids for the Outer Outer System. And you know
that whatever the mechanism that starts with big numbers
and then wastes them, many if not most of them would
have been scattered outward.


Sterling K. Webb
----------------------------------------------------------
----- Original Message -----
From: "Larry Lebofsky" <lebofsky_at_lpl.arizona.edu>
To: "Sterling K. Webb" <sterling_k_webb_at_sbcglobal.net>
Cc: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com>; "Ron
Baalke" <baalke_at_zagami.jpl.nasa.gov>
Sent: Friday, June 16, 2006 7:51 AM
Subject: Re: [meteorite-list] Three New 'Trojan' Asteroids Found Sharing
Neptune's Orbit


> Hi, Sterling:
>
> Not to burst your bubble, but a Trojan asteroid is called such because it
> is
> in a stable position with respect to the planet it is co-orbiting with.
>
> There are 5 what are called Lagrange points: L, L2, L3, L4, and L5.
>
> L1 is between the planet and the Sun (but lined up)
>
> L2 is outside the planet and again lined up.
>
> These two are unstable thanks to the pull of the gravity of the planet and
> the
> Sun. I think that there are man-made satellites in both of these, but they
> need small rockets to keep them there (I think SOHO is in L1 and that
> James
> Webb telescope will be at L2). Since they are closer or further from the
> Sun,
> their orbital periods would normally be shorter or longer than the Earth's
> (Kepler's Laws), but the gravity of the Earth helps a bit.
>
> L3 is on the other side of the Sun (anybody remember Man from Planet X or
> Journey to the Far Side of the Sun). Again, not a stable orbit due to the
> pull
> of the Sun and the planet.
>
> Finally, there are L4 and L5 (remember the L5 Society?). L4 is co-orbital
> with
> the planet and 60 degrees in front of it while L5 is co-orbital and 60
> degrees
> behind. These are fairly stable points (actually regions) which is why
> there
> are the leading and trailing Trojans of Jupiter. I think the four that are
> now
> known for Neptune are all in the leading zone.
>
> Actually, if you look at where the Jupiter Trojans are, they are
> actually "clouds," not points. I am not sure of the size of these, but
> they
> can be inclined to the orbit of Jupiter (as in the case of one of the
> Neptune
> ones), slightly closer or further from the Sun, or slightly in front of or
> behind the 60 degree point. In the case of Neptune, that is probably a
> fairly
> large volume.
>
> However, I still do not understand where they come up with the idea that
> they
> are more numerous than the asterod belt. All they have are four and yes,
> there
> may be bunches that are net seen because they are small and relatively far
> from the precise trojan points, but that is a long way from saying that
> there
> are more though, similar to what Sterling is saying, the volume is huge.
>
> Larry
>
>
>
> Quoting "Sterling K. Webb" <sterling_k_webb_at_sbcglobal.net>:
>
>> Hi, Everybody,
>>
>>
>> I think you know I am not too easily boggled (as in
>> "That's mind-boggling!"), but one sentence in this press
>> release boggled me: "Evidence suggests that the Neptune
>> Trojans are more numerous than... the asteroids in the
>> main belt " MORE Neptune Trojans than Main Belt
>> Asteroids, Gracie? Did I hear that right?
>>
>> My first thought was, "Where you going to put them
>> all?" and then I realized that if instead of just being in or
>> along Neptune's orbit, they are scattered all over Neptune's
>> orbital sphere, why, they would cover the surface of a
>> sphere with a diameter of 7,500,000,000 miles, and a
>> sphere with a diameter of 7,500,000,000 miles covers
>> one heck of a lot of real estate! (Way too many zero's
>> for this email!) Lots and lots of room to fit those millions
>> of big rocks into!
>>
>> The second realization was that the statement, "The methods
>> used to observe the asteroids are not sensitive to objects so far
>> out of tilt with the rest of the solar system" is a complete mouthful
>> of weasel-words for "We never bothered to point the big tube
>> in that direction. Doh." If you never point the scope at where
>> they are, your method is solidly 100% non-sensitive to them!
>>
>> Seriously, all searches are restricted to a band within a certain
>> selected number of degrees of the ecliptic on the assumption
>> that there are no more highly inclined objects to look for, on
>> a statistical likelihood. Guess what?
>>
>> More Neptune Trojans than Main Belt Asteroids, huh?
>> Are any of'em as big as Ceres? At closest approach a bright
>> Ceres-sized asteroid at Neptune's distance would be 535
>> times dimmer than Ceres is, about magnitude 13, fading
>> to 15 or 16 at other parts of its orbit, and if it were a
>> reddened object like so many other outer system objects,
>> still fainter by another magnitude or so.
>>
>> It's well to recall the disputed 2003 EL61, discovered by
>> Brown with a Big Gun but not announced and by a Spanish
>> team with a smaller telescope and announced, and verified by
>> getting a shot of it through a lousy 12-inch scope. Bright as it
>> was, it should have been discovered long ago but had never
>> been noticed, because of the fact that it's OUT OF PLANE!
>> Nobody looked...
>>
>> A slew of big bumpers beyond Pluto, some with moons,
>> and a Planet bigger than Pluto... er, CUSE ME, an "object"
>> bigger than the Planet Pluto. Now an asteroid belt as big or
>> bigger than the Main Belt, of probable planetesimals for those
>> Plutonian Planets I posted so tediously about last year... It's clear:
>> THE OUTER SYSTEM IS WHERE'S IT'S HAPPENING!
>>
>> Been thinking about Migrating to Mars?
>> Been saying that someday you're going to get in on the
>> Mining Boom in the Main Belt?
>> Forever threatening to Jump Off for Jupiter?
>> Yearning to buy that ticket for the Shuttle to Saturn?
>>
>> Forget it! It's a Waste of Time!
>>
>> The Outer Outer System is Where It's Happening!
>>
>> For further information,
>> contact OOSCC (the Outer Outer
>> System Chamber of Commerce) at
>> http://sww.ooscc.nep.triton.com/ or
>> http://sww.ooscc.pl.charon.com/
>> or visit one of our many entertaining Expo's
>> on a World or Satellite near you.
>>
>>
>> Sterling K. Webb
>
>
Received on Sat 17 Jun 2006 03:40:50 PM PDT