[meteorite-list] Trojan And Other Asteroids, Part Two

[Sterling K. Webb]

Hi, All,

    Having trouble posting.  If this a duplicate, delete.  Sorry

    In an earlier post, I pointed out that Venus Trojans would be
brighter and easier to spot.  Since then, I have been pondering that.
We're detecting minor minors at a fantastic (to me) rate these days.
There's always the problem of collecting more data than you evaluate,
stories of yet-unexamined Viking Mars data tapes crumbling to crackles
in vaults somewhere because there's no money to pay somebody to look at
them for the first time (don't know if it's true).  Every detection has
to be re-acquired to calculate orbital elements.  Is it done often
enough that some one would notice that an orbit was a Trojan?

    Except for when someone occasionally gets a wild hair about
searching for Vulcanoids or intra-Mercurial bodies, astronomers do
not willingly work the sky near the Sun for obvious reasons: it'
difficult, very hard to do, constricted in observing times, no really
dark skies, messy, frustrating and probably worthless. And solar
telescopes never look away from the bright god they study.

    Many volunteers search the SOHO images for comets (all of them?)
plunging toward the Sun and are finding them by the hundreds while
sitting on their butts in front a computer just like I'm doing now.
There are LOTS of objects in the inner system coming and going all
the time!

    Yet, when you turn to minor planet lists you see crowds and crowds
of stuff outside the Earth's orbit and very little inside it.  You could
call the inner system "depleted."  To me, that doesn't make sense. In
countless computer simulations of encounters in the outer system over
the decades, most (80%) perturbed objects are ejected from the solar
system completely, and some (20%) are sent into the inner system.  If
20% of all encounter generated orbit changes send bodies inward and if
this persists for the lifetime of the solar system, the inner system
should not be "depleted" of objects. Inner system terrestrial bodies
have the the millions of craters to prove it just ain't so. That was
then.

    This is now. The inner system bodies we know of rarely have
long-term stable orbital dynamics.  You can expect most NEA's to last
up from a million to ten million years, a fraction of a percent of
the age of the solar system.  Therefore, the inner system must be
continually resupplied to maintain the reservoir.  I think that
reservoir is larger than we think. We have been deceived by a
"selective observer effect." It's hard to search, so we don't
search as much, so we don't find, so if we don't find, it ain't
there, so we search less, and so on. in a feedback cycle. It was
hard to get people to search for NEA's.

    Then, there's what I call the "LeVerrier-Lescarbault Effect."
The great discoverer of Neptune, LeVerrier, was convinced by an
amateur astronomer, Lescarbault, that he, Lescarbault, had observed
the transit of a small planet with an orbit inside of Mercury's, the
planet Vulcan. In retrospect, it's clear that Lescarbault's
observation, although possibly real, was vague and imprecise,
untimed and not of much use, and his equipment was junk, but
LeVerrier jumped on the discovery, in which he believed to his
dying day, recalculating the "orbit" and trying to re-acquire it.
Don't suppose the lure of being the only man in history with TWO
planets to his name had anything to do with that, do you?

    Since that incident, professional astronomers have a wise and
natural reluctance to even think about investigating the inner system
for small bodies, understandably, "I'll pass on that."  The XIXth
century is over-run with numerous discoveries of small inner system
bodies never recovered, and with that grade of equipment, transits
were about your only chance to detect an inner system minor planet.
Is EVERY old observation of this kind just a whacko aberration?
Probably not.

    During the 29 June 1878 solar eclipse, two experienced astronomers,
Professor James Craig Watson, director of the Ann Arbor Observatory in
Michigan, and Lewis Swift, an amateur from Rochester, New York, both
claimed independently to have seen a "planetary" object close to the
Sun at totality, about magnitude five or six.  These guys were not
jerks nor incompetent.  Watson was the discoverer of 20 confirmed minor
planets (a lot in those days) and Swift was the discoverer of a number
of comets some of which you've probably heard of as they bear his name.
They knew what they we doing. Both saw a detectable disk, not a
bright point.

    Because their positions for the object differ from each other more
than can be accounted for by the Earth distance between Wyoming and
Colorado (where they respectively were), that half-degree parallax says
to me that they observed a honking big asteroid in the inner system that
was actually passing very close to the Earth and only incidentally in
line with the Sun at the time of eclipse.  Its relative motion could
account for some of the parallax, but eclipse totality observing time is
very short, not long enough to observe relative motion.  Did we have a
coincident "near miss"?

    A number of distinguished XIXth century astronomers saw mysterious
solar transits of short duration, which they always interpreted as a
body close to the Sun because of it.  They had planets on the brain. 
Finding a planet would make you "immortal."  But a short transit is just
what you'd expect if a NEA made a daytime close approach to the Earth. 
By the next night, it would be long gone beyond the magnitude limit of
XIXth century equipment.  The fact that no Vulcan or Vulcanoid
observations were ever repeated or recovered only strengthens the case
for a potential NEA close-approach observation.

    In the famous Lescarbault transit of so-called Vulcan, "an eminent
French astronomer, Emmanuel Liais, who was working for the Brazilian
government in Rio de Janeiro in 1859, claimed to have been studying the
surface of the Sun with a telescope twice as powerful as Lescarbault’s
at the very moment that Lescarbault said he witnessed his mysterious
transit. Liais, therefore, was 'in a condition to deny, in the most
positive manner, the passage of any planet over the sun at the time
indicated' (Popular Science, Volume 13, pages 732-735, 1878)."  I say,
parallax again.  The object was real; it just wasn't near the Sun but
the Earth!  Close enough to be in line with the Sun from France; off
to the side from Brazil, 8,000 miles away.

    In 1970, Henry C. Courten found what he believed to be an
intra-Mercurial object or objects in eclipse photos, and hypothesized an
intra-Mercurial asteroid belt, the Vulcanoids.  The idea was logical
enough.  Rubble trapped close to the Sun's gravity ain't going nowhere! 
It was a good enough idea to inspire several searches, but nothing was
found, of course.  Checking back, I discover they couldn't have found 
anything smaller than 100 kilometers, anyway.  Still looking for a
planet, Vulcan size, not asteroids, if you ask me.

    If there are Vulcanoids, they are not a threat like NEA's.  SOHO
images contain a number of small anomalous objects that are routinely
and thoughtlessly ignored.  They aren't comets, so who cares?  They
show no coma, are often irregular in outline, and much fainter.  Gee,
wonder what they could be?

    To better understand my parallax argument, look at it this way.  The
Sun covers one half degree of the sky; it's almost a million miles
across, but it's almost 100,000,000 miles away.  An object half the size
of Mercury 10,000,000 miles from the Sun, like the imaginary Vulcan, was
said to have shown a disk about 1/500 to 1/800th of the size of the
Sun's disk.  If that object were only ten million miles away from the
Earth, instead of 10,000,000 miles from the Sun, it would have only been
a 150 kilometer body.

    Working our way down that scale of things, If that object were only
one million miles away from the Earth, it would have only been a 15
kilometer body (Chicxulub).  If that object were only 100,000 miles away
from the Earth, it would have only been a one mile body (too many of
those to even try a name).  That's bigger than any bodies we have
OBSERVED to have passed within the Moon's distance, but since literally
dozens of smaller bodies have done so in the last decade, it's not an
impossibility by any means.

    And in the most fascinating case (to me), if a one mile body were to
just barely miss us, not quite grazing the Earth's atmosphere at 150
miles of altitude (boy, you can't get a nearer miss than that!), it
would eclipse the Sun COMPLETELY, covering the entire solar disk exactly
as the Moon does in a "normal" solar eclipse, but only visible in a very
narrow precise path.  The duration of totality would be 0.1 to 1.0
second, and the width of the umbral path would be... one mile, same as
the asteroid.

    So, if you're ever out in the open flat land and see a mile-wide
shadow like a highway of darkness racing straight toward you, the Sun
blink out for a second when it reaches you, and turn to watch a
vanishing ribbon of blackness speeding away from you in a straight line,
you run and tell somebody, OK?

    Since the largest sunspots, those over about 120 arc-seconds, or
about 6% of the Sun's diameter, are clearly visible to the naked human
eye (careful!), an Earth close-approach object transiting the Sun, one
about 3 arc-minutes or more in diameter, would be very noticeable,
particularly on an overcast day, and since the transit would last some
minutes, last long enough to be noticed.

    There are a small handful of XIXth century anomalous daytime
transiting object reports, reported by "ordinary" people, not
astronomers, all seen in a single narrow locality but nowhere else,
lasting for a few minutes up to twenty minutes, and most describing
the dark object not as a round spot, but irregular, "like a fist,"
a "mountain," or a "potato." (The famous potato strikes again.)
Ten close approaches per century by a good sized object is not out
of the question if there are more of them than we think there are.



Sterling K. Webb
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