[meteorite-list] Earth Trojan asteroids

[Francis Graham]

Streling K. Webb wrote:
 "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.  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), the 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 "near miss"?"

  Sterling and list, if it was real, it was a near
miss closer than you realize. A near Earth asteroid
passing in the direction of the Sun can be captured.
Recall JE002E4, the temporary "extra moon" of Earth
2002-2004 that may have been a Saturn stage.

Francis





--- "Sterling K. Webb" <kelly at bhil.com> wrote:

> Hi, All,
> 
>     The other web page in my first post about Earth
> Trojans:
>    
>
<http://www.astro.uwo.ca/~wiegert/etrojans/etrojans.html>
>     has lots of animated GIF's, nifty diagrams, and
> downloadable MPEG movies of the
> dynamics of the Trojan points, along with an
> explanation that is almost as good as
> MexicoDoug's!
>     You can't beat all those bright moving colors in
> an explanation, I always say.
> 
>     And while we've been thrashing the topic of
> asteroid 3753 Cruithne, to which I will
> refer to as "Crazy Cruithne" from now on, to death,
> the REALLY interesting thing to me
> I found on that site (above) was a detection image
> of what may turn out to be a true
> Earth Trojan! (You have to track it a long time to
> be sure.)
> 
>     A real Earth Trojan.  That would be wonderful if
> verified.
> 
>     They don't give the magnitude of the potential
> Trojan object, but since they're
> using the big Canada-France-Hawaii telescope, I
> eyeball it by comparison with fainter
> objects in the frame at perhaps magnitude 21 or so? 
> That would make it about 300 to
> 600 meters, roughly.  But I'm guessing.
> 
>     They search 9 or 10 square degrees of sky
> (because of those loopy "halo" orbits)
> and at this scale, that's a lot of territory to
> cover searching by tiny, tiny patches.
> They don't say how much of that territory they've
> covered, searching for an always
> moving target, and don't say if they continue to
> search. If you've ever had the
> experience of inadvertently "losing your way" while
> examining something under a high
> power microscope, you know what I mean. "Where did
> it go?!"
> 
>     I once had a "choice" summer job at my school, a
> temporary electron microscope
> operator.  If you think it's easy to "get lost" at
> 500X, try 50,000X! Incredibly
> frustrating when it occurs to you that it's like
> search a square kilometer area one or
> two square centimeters at a time!  Of course, my
> boss only did that a few times, and
> only to impress on my youthful ego how little I
> really knew (very necessary), then set
> me on simpler routine tasks at lower powers and gave
> the important jobs to the "real"
> operators.  I was a crackerjack calibrator, though. 
> Picky, picky, picky.
> 
>     Magnitude is a whacky unit of measure.  When old
> Ptolemy made the first star chart
> in all of history (that we know of), he naturally
> wanted to indicate the relative
> brightness of the individual stars compared to each
> other.  It wouldn't be very useful
> to puts lots of equally tiny dots all over the first
> skymap.
> 
>     But stars are points on the sky, no matter how
> bright, so you can't make the
> brightest ones huge fat blobs.  He knew of course
> that a dot twice the size of another
> dot had PI times as much area and so could indicate
> a star PI times as bright, but that
> was too big a step and the biggest dots weren't big
> enough.
> 
>     Close, but not quite right.  You don't need to
> make a dot twice as big for people
> to see easily and intuitively that one is bigger
> than another.  A 50% or so increase in
> diameter is enough for that.  Besides, PI was a
> mysterious thing to the Greeks, a
> religious secret if you were a Pythagorean, and
> IRRATIONAL.  The Greeks just hated
> that.
> 
>     Ptolemy was estimating the stellar brightnesses
> by eyeballing and comparing them.
> Great astronomer; no telescope. He knows he can
> reliably group stars by brightness when
> one is about 2.5 times brighter or dimmer than
> another, so he stages up the size of the
> dots to correspond to a scale of "magnitude" in
> which each increase in one "magnitude"
> is a star 2.5 times brighter than a star with next
> smallest dot on The Great Chart.
> 
>     In so doing, he invents the first logarithmic or
> power scale in human history!  I
> don't think he appreciated what he did or how useful
> the notion of logarithmic scales
> could be.  Of course, maybe he did, but kept it his
> own little secret, as there are
> stories that other scholars brought him hard messy
> numerical problems to which he would
> smilingly hand back the answer to the next day.  No
> problemo.  Glad to help out,
> Anaximos, old buddy.  A good trick always helps your
> reputation as a genius, you
> know...
> 
>     OK, he got that whole structure of the solar
> system thing wrong...  Nobody's
> perfect.
> 
>     The modern magnitude scale is based on powers of
> 2.512, a snap to calculate with
> cheap modern calculators.  In the "old days" there
> were tables of magnitude to
> luminosity conversion in fine print by the 0.1
> magnitude step, with little rows off to
> the side to interpolate the 0.01 steps, just like
> there were for regular logarithms.
> That was in the era when a simple four function
> calculator like you can buy for 99
> cents in the Dollar Store or Target today cost $1500
> straight from Remington Rand! (And
> couldn't have done the job, anyway.)
> 
>     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 get 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's 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 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!  Most of them comets,
> which is what these folks are looking for.
> 
>     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.  To me
> that doesn't make sense.  The outer
> system has big nasty gravitational perturber
> planets, and objects have slower orbital
> velocities that make them easier to perturb.  There
> is more room out there, but there
> are more stable orbits inward, where you find
> orbital oddities like "Crazy Cruithne."
> That orbit would never last in the outer system.
> 
>     I think it's what we call a "selective observer
> effect."  Way off, sitting on the
> porch of my dream shack in my own personal Hunch
> Land, I think there's lots of stuff
> running around in the inner system.  Why should it
> be different than the rest of the
> solar system?  Our special position?  Home turf?  No
> space junk here; this is a nice
> neighborhood?   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 cycle.
> 
>     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
> 
=== message truncated ===


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