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• Information circulated on the cambridge-conference network is for
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CCNet 70/2001 -  22 May 2001
----------------------------


"About the time of the Hale-Bopp appearance in 2213 BC, there seems
to have been a widespread collapse of ancient civilization, followed by an
apparent lengthy dark age. So I wrote up the following and sent it
around to a few scientists who had commented on the comet, and to
several publications. I got almost no response, and as far as I know, it was
never published. It seems like a good enough idea for research into
idea-generation to include here. [...] Not only did two great ancient
civilizations suddenly collapse and enter into chaos for over a century
- sinisterly coincident with the previous appearance of comet
Hale-Bopp - a cataclysmic event, followed by a serious sudden temporary
climate change, appears to have taken place at the onset of the
collapse. Did some large part of comet Hale-Bopp collide with our
delicate small blue planet in 2213 BC? Clear in our present memory are
those remarkable Earth-based and space telescope photographs of Comet
Shoemaker-Levy, broken up into a string of giant objects, serially colliding
with the giant planet Jupiter between July 16 and July 22, 1994. Is it
possible that the comet Hale-Bopp we saw for a month in the spring of
1997 is only a part of a once larger comet that appeared in 2213 BC?
Might some of the rest of that comet now be part of the matter of our
planet Earth after having collided with it in 2213 BC?"
--Tom Slattery, About Ancient/Classical History, 21 May 2001


(1) COMET CATASTOPHE: A SPECULATIVE FEATURE BY TOM SLATTERY
    Robert Clements <Robert.Clements@dva.gov.au>
 
(2) MISSING CARBON-2 MOLECULE HOLDS CLUES TO COMET'S ORIGIN
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(3) COPYCAT COMET CRACKS INTO THREE PIECES, MAYBE MORE
    Space.com, 21 May 2001

(4) COMET'S DEMISE REVERSES 'DIRTY SNOWBALL' THEORY
    Los Angeles Times, 21 May 2001

(5) WHAT WE LEARNED FROM COMET LINEAR
    John Wagoner <stargate@astromax.com>

(6) WILD WIDE UNIVERSE
    The Hindu, 21 May 2001

(7) COMET C/1999 S4 (LINEAR)
    Comets & Meteor Showers

(8) PYRAMIDS IN THE SKY
    Duncan Steel <D.I.Steel@salford.ac.uk>

(9) SHAPE OF PYRAMIDS
    Rolf Sinclair <rolf@santafe.edu>

(10) IMPACTS & HUMAN EVOLUTION
     Worth Crouch <doagain@jps.net>

(11) MORE OBSERVATIONS OF SHOEMAKER-LEVY 9 IMPACT
     de Pater I, Brecht SH: SL9 impacts: VLA high-resolution observations at
lambda=20 cm

(12) MODIFICATION OF THE JOVIAN RADIATION BELT BY SHOEMAKER-LEVY 9
     Brecht SH, de Pater I, Larson DJ, Pesses ME
 
(13) THE SHOEMAKER-LEVY 9 IMPACT & ENHANCED RADIAL DIFFUSION
     de Pater I, Brecht SH: SL9 impacts and simulations of enhanced radial
diffusion

(14) FORCED PRECESSION MODELS FOR SIX ERRATIC COMETS
     Krolikowska M, Sitarski G, Szutowicz S: Forced precession models for
six erratic comets

(15) THE ORBIT EVOLUTION OF 32 PLUTINOS OVER 100 MILLION YEARS
     Wan XS, Huang TY: The orbit evolution of 32 plutinos over 100 million
year

(16) THE CHEMISTRY OF INTERSTELLAR SPACE
     Herbst E: The chemistry of interstellar space


========
(1) COMET CATASTOPHE: A SPECULATIVE FEATURE BY TOM SLATTERY

From Robert Clements <Robert.Clements@dva.gov.au>
 
As posted on About Ancient/Classical History
From N.S. Gill, your Guide to Ancient/Classical History
<http://ancienthistory.about.com>
May 21, 2001
Volume V Issue 21 ISSN: 1521-9232
 
GUEST FEATURE
 
COMET CATASTOPHE. A SPECULATIVE FEATURE BY TOM SLATTERY

"Did our ancient ancestors get bopped by a fragment of Hale-Bopp? If so,
where did it hit? And: might there be another fragment following Hale-Bopp
out there that could intersect with our planet's orbit? Again?"
http://ancienthistory.about.com/library/bl/bl_slattery_comet.htm

About the time of the Hale-Bopp appearance in 2213 BC, there seems to have
been a widespread collapse of ancient civilization, followed by an apparent
lengthy dark age. So I wrote up the following and sent it around to a few
scientists who had commented on the comet, and to several publications. I
got almost no response, and as far as I know, it was never published. It
seems like a good enough idea for research into idea-generation to include
here.

COMET-CAUSED COLLAPSE OF THIRD MILLENNIUM BC CIVILIZATIONS?

As the newly discovered Comet Hale-Bopp grew brighter in the early spring of
1997 and eventually made a remarkable nightly appearance lasting about a
month, speculation about its calculated previous appearance in 2213 BC and
resultant effects on our early ancestors seeing it at dawn of civilization
began to be exchanged. But nothing could be found in the scant written
records of these early civilizations.

Newsweek, March 24, 1997, page 60, noted a scramble to discover contemporary
mention of the comet's last appearance over four millennia ago had turned up
nothing in the spotty records of ancient China, the Mohenjo-daro
civilization of the north Indian subcontinent, ancient Mesopotamia, and
ancient Egypt. A mere mention would certify one or more of the presently
shaky archeological chronologies, so experts on ancient civilizations would
seem to have been powerfully motivated to scrutinize the scanty surviving
records to find even a surviving mythological allusion. And yet, so far they
have found nothing.

That is, at very least, curious. The absence of ancient record may strike
those familiar with ancient acute fascination for celestial events as
indicating something significantly lacking in either ancient records or in
archeological discovery of them. What could be wrong?

A disturbing answer is that perhaps there may have been observation. The
comet may have been seen. But before careful observations could be recorded
- possibly awaiting final official decisions on portents, or maybe simply
waiting a normal cyclical resolution to the heavenly phenomenon - a
disastrous collision with Earth by a significant comet fragment may have
taken place. And this caused sudden catastrophic global climate changes.

Coincident with the previous appearance of Comet Hale-Bopp in 2213 BC,
something singularly dreadful seems to have happened on our small fragile
blue planet. Not only does it appear that both the ancient Mesopotamian and
Egyptian civilizations totally collapsed for a century or more, there is
evidence of a sudden catastrophic-but-temporary climate change at this time.
Is there a "bad weather" connection? Should we be concerned with the
connection if there is one?

It is unlikely that the date 2213 BC could be wrong, although over the past
four millennia it is conceivable that something gravitationally significant
may have intersected with the orbit of comet Hale-Bopp and altered it, thus
changing the date of its last appearance. But astronomically speaking, 4200
years is fairly insignificant, and objects with that much serious gravity
are pretty sparse in space. So the orbit-extrapolated date of 2213 BC would
seem reliable.

It would seem that Hale-Bopp made at least a notable if not spectacular
appearance in the night sky four millennia ago, and the astronomy-based
state religions of numerous centers of early agricultural civilization would
have noted and recorded it either in official religious mythology or in
observed fact, and somewhere at least fragment should have survived. But
there appears to be no recorded mention.

Whatever happened that led to the remarkable omission would seem to have
happened swiftly and planet-wide here on Earth. And while records from the
ancient Mesopotamian and Egyptian civilizations mention no comet, they do
contain suggestions of a catastrophe that may leave us with some worrisome
implications for our near or distant future.

The ancient Egyptian chronology used by Egyptologist Aidan Dodson in his
1995 book Monarchs of the Nile, based on latest research, has the pharaoh
Pepi II (prenomen Neferkare) ruling Egypt between 2290 and 2196 BC when
Hale-Bopp is calculated to have last appeared in 2213 BC. According to this
dating system, comet Hale-Bopp would have made its appearance in the 77th
year of good king Pepi's reign.

But there is something puzzling about Pepi II. According to the surviving
records, his reign lasted 94 years. Egyptologists have gone into figurative
contortions to explain this. The prevailing view is that Pepi's accession
came when he was only six, and that he lived to be a hundred. But, as Dodson
mentions, some have suggested that Pepi's long reign should be reduced to
sixty-four years. The length of the reign, then, is, at very least, in
dispute. And given the difficulties in precise dating, 64 years is close
enough to to the year 77 of Pepi II's reign, when the comet would have
appeared, to raise questions about the causes of its end.

What is not in dispute is what followed the reign of Pepi II. The next
pharaoh, Nemtyemsaf II, lasted a year, probably a fraction. Then, in 2195 BC
(if we accept the ninety-four-year reign, or 30 years earlier, 2225 BC, or
maybe somewhere in between like 2213 BC?), came a period of such political
and record-keeping chaos that not only is it called the First Intermediate
Period, but the dynasties are uncertain and called "VII" and "VIII," and
even the next two dynasties following the First Intermediate are
conspicuously puzzled-out and called "Dynasties IX/X" and "Dynasty XIa." The
period of confusion between the present disputes for the end Pepi II's reign
and the end of Dynasty XIa thus goes from just prior to or just after 2200
BC to 2066 BC, about a century to a century and a half.

Something happened at about the time the comet appeared that threw Egypt
into chaos for a number of generations, several lifetimes, long enough for
word-of-mouth memory to forget. It appears to have occurred suddenly, caused
chaos, and by the time chaos ended generations later, the initiating series
of events were no longer part of living memory.

Corroboration comes from Mesopotamia. Something brought down the Akkadian
civilization.

Around 2200 BC - give or take at least a decade in the approximate dating
and close enough to the comet's last appearance to raise questions -
civilization collapsed. Reference to the initial collapse is contained in
"The Curse of Naram-Sin," a clay-tablet docu-drama about transgression and
heavenly punishment of the last king of Akkad, Naram-Sin. In it, hill people
known as the Guti, probably ancestors of the modern Kurds (and possibly the
same word if one pronounces "Guti" with a combination of a Boston accent, a
soft "G" and a hard "t" to make it "Kurdi") overrun Akkad amid allusions to
a sudden climate change. Subsequently people we call the Amorites, whom the
Sumerian script calls the MARTU (who spoke a language closer to Hebrew than
Akkadian), appeared from the west and overran what would appear to be a
futile attempt to restore the Akkadian Empire from the ancient city of Ur.
This was followed - in Mesopotamia, as would appear to have simultaneously
occurred in Egypt - by a period of chaos lasting a century and a half to two
centuries.

Two independent areas of ancient civilization collapsed at about the time
comet Hale-Bopp last appeared. That should be troubling. The sudden
appearance of a strange celestial object might cause temporary panic in the
populations of these two ancient empires. Indeed we see the same phenomenon
in the cult-suicide of Applewhite and his followers even in our enlightened
scientific age. But temporary panic would hardly seem sufficient to have
brought about the kind of serious political and economic collapse that
lasted over a century in both ancient areas of civilization.

A group of Yale University archaeologists and scientists investigating the
period at an archeological site in Mesopotamia called Tell Leilan has
uncovered something that in this context may summon a scary scenario. In an
article in Science, 20 August 1993 (page 995) titled "The Genesis and
Collapse of Third Millennium North Mesopotamian Civilization," Weiss, et al,
found, if I may quote a bit of the abstract: "At 2200 B.C., a marked
increase in aridity and wind circulation, subsequent to a volcanic eruption,
induced a considerable degradation of land-use conditions. After four
centuries of urban life, this abrupt climate change evidently caused the
abandonment of Tel Leilan."

Not only did two great ancient civilizations suddenly collapse and enter
into chaos for over a century - sinisterly coincident with the previous
appearance of comet Hale-Bopp - a cataclysmic event, followed by a serious
sudden temporary climate change, appears to have taken place at the onset of
the collapse.

Did some large part of comet Hale-Bopp collide with our delicate small blue
planet in 2213 BC? Clear in our present memory are those remarkable
Earth-based and space telescope photographs of Comet Shoemaker-Levy, broken
up into a string of giant objects, serially colliding with the giant planet
Jupiter between July 16 and July 22, 1994.

Is it possible that the comet Hale-Bopp we saw for a month in the spring of
1997 is only a part of a once larger comet that appeared in 2213 BC? Might
some of the rest of that comet now be part of the matter of our planet Earth
after having collided with it in 2213 BC?

What effect would a high-speed impact of a several-mile-diameter giant
snowball have with our planet's landmass, in, say far away North America,
Siberia, or Australia - in other words far enough from Egypt and Mesopotamia
not to have been recorded as the cause of devastating effects? It seems
conceivable that the impact could throw up debris similar to that of a
volcanic eruption, or alternatively, it would seem that the resultant giant
vapor cloud could bring about, first, a solar-energy occlusion, and then a
resulting sudden mini-ice-age, and then planetary water-weight shift would
precipitate increases in volcanic activity adding magnitude to the temporary
climate change.

The coincidence of (1) the comet Hale-Bopp's last appearance in 2213 BC, (2)
the total collapse of two significant ancient civilizations for over a
century beginning around 2200 BC, and (3) good evidence of a sudden
climate-changing catastrophe around 2200 BC seems too much for thoughtful
folks to ignore. Something sudden and terrible, associated with the comet
Hale-Bopp, would appear to have happened.

Did our ancient ancestors get bopped by a fragment of Hale-Bopp? If so,
where did it hit? And: might there be another fragment following Hale-Bopp
out there that could intersect with our planet's orbit? Again?
 
© 2001 About.com, Inc.

============
(2) MISSING CARBON-2 MOLECULE HOLDS CLUES TO COMET'S ORIGIN

From Andrew Yee <ayee@nova.astro.utoronto.ca>

Office of Public Affairs
University of Texas-Austin
P O Box Z
Austin, Texas 78713-7509
(512) 471-3151
FAX (512) 471-5812

Contact:
Rebecca Johnson or Mary Lenz
Office of Public Affairs
(512) 475-6763

Missing carbon-2 molecule holds clues to comet's origin

AUSTIN, Texas -- Astronomers seeking to chart the solar system's evolution
reaped a windfall of information when a comet disintegrated just as it made
its closest approach to the sun and they were able to observe the comet's
contents and, possibly, its origin.

Their work will be published Friday (May 18) in the journal Science -- a
special issue devoted to studies of the comet, called C/1999 S4 (LINEAR),
that disintegrated last July.

Dr. Tony L. Farnham, a planetary scientist at The University of Texas at
Austin, and his colleagues discovered a deficiency in the molecule carbon-2
in Comet C/1999 S4 (LINEAR). Farnham, lead author of the paper, is the
Harlan J. Smith Planetary Post-doctoral Researcher in the UT Austin
department of astronomy. (LINEAR refers to the Lincoln Near Earth Asteroid
Research project funded by the U.S. Air Force to study near earth objects.)

Co-authors include Dr. David G. Schleicher and Dr. Laura M. Woodney of
Lowell Observatory in Flagstaff, Ariz.; Peter V. Birch of Perth Observatory
in Western Australia; Clara A. Eberhardy of the University of Washington in
Seattle; and Lorenza Levy of Northern Arizona University in Flagstaff.

"We usually get a look at the surface of a comet, but this time we got to
look inside," Farnham said. The group observed the comet both before and
after it broke up, using telescopes at UT Austin's McDonald Observatory,
Lowell Observatory and Perth Observatory.

Comets are sometimes referred to as 'dirty snowballs,' because they are made
up of dust and rock held together by ice. When they venture close to the
sun, the ice vaporizes and elements inside are released.

The carbon-2 deficiency discovered by Farnham and his colleagues indicates
that the comet formed near Neptune, probably billions of years ago. Most
comets were formed during the solar system's earliest years in two regions:
near Jupiter and Saturn, and farther out, near Neptune.

They didn't stay in those regions, however, because the force of gravity of
those giant planets catapulted the comets away, and created two comet
habitats: the Oort Cloud (a halo of Jupiter-origin comets enveloping the
solar system) and the Kuiper Belt (a belt of Neptune-origin comets orbiting
in the plane of the solar system along with the planets, beyond Neptune's
orbit).

Different lines of evidence may indicate another history for C/1999 S4
(LINEAR). Other researchers found the comet to be lacking in other
carbon-chain molecules, pointing to a Jupiter-region origin, Farnham said.
He said the discrepancy "may be telling us that it has a surface  material
different from what's inside. It's possible that the comet formed near the
Jupiter region, and other materials formed on the surface as it migrated
out," into the outer solar system. But Farnham cautioned that there is no
proof of this.

Understanding the origin of comets is important because they carry key
information about the history of the solar system that cannot be derived
from studying planets. Comets have changed very little since the solar
system formed. They are relics of an earlier time. Geological processes
(like volcanic eruptions and the movements of glaciers) have rewritten the
surfaces of most of the planets since their formation.

"Comets have been in storage, especially dynamically new comets, like this
one," Farnham explained. He said comets remain in the cold realms of the
Oort Cloud and Kuiper Belt until some large body like a planet or a passing
star gives them a gravitational kick into the inner solar system. A
'dynamically new' comet is one that has never been in the inner regions of
the solar system before.

Farnham also calculated a lower limit for the radius of the comet's nucleus
before break-up: about 0.4 kilometers. In addition, he observed an
'outburst' from the comet, at the same time other researchers using the
Hubble Space Telescope photographed a piece of the comet breaking away.
Comet C/1999 S4 (LINEAR) was not visible to the naked eye.

For more information, contact Dr. Tony L. Farhnam at (512) 471-1483, or via
e-mail at farnham@astro.as.utexas.edu or see:
     http://www.ll.mit.edu/LINEAR
 
============
(3) COPYCAT COMET CRACKS INTO THREE PIECES, MAYBE MORE

From Space.com, 21 May 2001
http://www.space.com/scienceastronomy/solarsystem/comet_breakup_010521.html

By Robert Roy Britt
Senior Science Writer

If copyright laws applied to cosmic acts, then Comet 2001 A2 would be in
court right now.

First it broke into two pieces earlier this spring just after a rapid
brightening session. Now one of those two chunks has split apart and
researchers say there may be many smaller pieces flying through space.

If the scenario sounds familiar, it's because this isn't the first comet to
break apart in recent months. The disintegration act comes less than a year
after another comet, called 1999 S4, broke into several large pieces and
countless smaller ones, all in plain view of numerous telescopes. That event
led to a bevy of revealing scientific papers on comet formation that were
released just last Thursday.

Both of these comets have been popularly called "LINEAR," named after the
Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research
telescope, which was used to discover them.

The most recent LINEAR comet, 2001 A2, was discovered just this year on Jan.
3 and presumed initially to be intact. It brightened suddenly and
unexpectedly back in March and April. As comets approach the Sun, their
nucleus of gas and dust burns off and forms a halo, or coma, that glows with
reflected sunlight.

Then on April 30th, researchers at the University of Arizona's Lunar and
Planetary Laboratory photographed the comet after its nucleus had broken
into two pieces. When a comet breaks apart, more fresh material is exposed,
which likely contributed to the sudden brightening.

The latest split

Now the comet is about 62 million miles (100 million kilometers) from Earth,
but it is no longer visible from the Northern Hemisphere. On May 14,
scientists using a European Southern Observatory telescope in Chile noticed
that one of the comet's two fragments appeared to be elongated.

On May 16, last Wednesday, it became clear that the comet had split into
three pieces. A colorful image of the latest breakup was released Friday.

Hermann Boehnhardt of the European Southern Observatory works on the team
that spotted the three large chunks. He told SPACE.com that the orbit of
2001 A2 is so different from 1999 S4 that the two comets are not likely
close relatives in terms of where they were created in the disk of gas and
dust that swirled around our Sun when it was born.

Depending on what the comet does in coming months, Boehnhardt said,
additional observations might allow researchers to figure out where it
formed and why it broke apart.

Drifting apart

When Boehnhardt and his colleagues first spotted the comet in three pieces,
roughly 310 miles (500 kilometers) separated the two freshly-split chunks.
The distance between this pair and the other piece was about 3,700 miles
(6,000 kilometers) on May 14 and increased by about 620 miles (1,000
kilometers) within two days.

No one can yet say how big the pieces are or how large the comet's nucleus
was before it broke apart.

The comet moves in an exceedingly elongated orbit around the Sun and it is
making perhaps its first return trip to the inner solar system after a long
hiatus in the Oort Cloud, a halo of comets that surrounds the solar system.

If it is the comet's first pass, that means it has not been in the main part
of the solar system since back when it formed, likely about 4.6 billion
years ago when the rest of the solar system developed. Its contents would be
pristine, and researchers will be interested to study it and see if it adds
to the long list of discoveries made by observing the other LINEAR comet
that broke apart last summer.

Where it is, where it's going

Comet 2001 A2 can now be seen with the unaided eye by observers in the
Southern Hemisphere as a faint object in the southern constellation of Lepus
(The Hare).

It will pass through its perihelion -- the point in its orbit nearest to the
Sun -- on May 25, at a distance of about 72 million miles (116 million
kilometers). Then it will reappear in Northern Hemisphere skies at the end
of June after it swings under the Sun. By then, it might be visible to the
naked eye, though that is not certain and its recent further disintegration
clouds that possibility.

Hal Weaver, a Johns Hopkins University researcher involved in the recent
studies of Comet 1999 S4 that broke up last summer, said it's possible the
same fate might await 2001 A2.

"We'll have to keep watching over the next several months," Weaver said.
Meanwhile, he's working on a French-led team making plans to observe 2001 A2
with the Hubble Space Telescope, likely in July.

Copyright 2001, Space.com

===========
(4) COMET'S DEMISE REVERSES 'DIRTY SNOWBALL' THEORY

From Los Angeles Times, 21 May 2001
http://www.latimes.com/news/science/science/20010521/t000042583.html

From Times Staff

Astronomers watching the "under-performing" Comet Linear last July were
astounded when it unexpectedly burst apart, offering them a direct view of
its internal structure in its disintegrating heart. Icy comets are usually
described as "dirty snowballs." Linear was comprised of rocky matter with
only a little ice, making it more of a "snowy dirtball."

Its fragments, scientists reported in the May 18 issue of the journal
Science, appear to be the same material that makes up planets. The comet was
relatively free of carbon-rich compounds observed in the ice of other
comets, casting some doubt on the theory that comets delivered the precursor
molecules necessary for life on Earth.

Copyright 2001, Los Angeles Times

==========
(5) WHAT WE LEARNED FROM THE LAST YEAR'S COMET LINEAR

From John Wagoner <stargate@astromax.com>

SKY & TELESCOPE'S NEWS BULLETIN - MAY 18, 2001
For images and Web links for these items, visit http://www.skypub.com

Last June, amateur and professional astronomers alike focused their
telescopes on what was thought to be a mediocre comet as best. Discovered by
the Lincoln Near Earth Asteroid Search, Comet LINEAR (C/1999 S4) soon became
a cosmic curiosity. In Hubble Space Telescope observations taken in July,
the comet appeared to have erupted, with a large fragment having clearly
broken off the nucleus. In the month that followed, the comet crumbled apart
completely, faded from view, and in the process, exposed its interior to
science.

In a series of papers published in today's Science, astronomers reveal what
they have learned thus far from the deceased comet. In addition its chemical
composition and probable origin, (see following story) astronomers now think
they may understand why the comet came apart in the first place. Originally
they assumed that Comet LINEAR's breakup was due to massive outgassing --
perhaps the result of an outburst of carbon monoxide (CO), the most probable
suspect. However spectroscopic analysis found the comet to be highly
depleted of CO, thus making a pressure build-up of gas within the nucleus an
unlikely cause.

Instead, Hal Weaver (Johns Hopkins University), author on three of the
Science papers, believes the comet was most likely rotating quickly on its
approach to the Sun. If the rotation pole was pointed toward the Sun, says
Weaver, "there would be more efficient heat transfer throughout the comet."
But he adds that it isn't clear the comet was rotating fast enough to break
apart. The critical rotation speed depends largely on the initial size of
the comet's nucleus, a quantity
yet to be determined.

Another interesting facet of Comet LINEAR is what wasn't seen. The assumed
mass of the comet before it crumbled is 100 times larger than the mass found
afterward. Some of this is to be expected. Larger blocks are directly
detectable, as are the smallest of particles, which refract light much the
same way a thick fog would. But just as a thick fog easily hides all but the
largest of objects from view, so too did LINEAR's dust cloud.

"Watching the unraveling of the comet allows us to look in reverse at its
formation," says Weaver. Thus determining the size of the intermediate
fragments directly relates to the size of cometary nuclei in general. An
abundance of intermediate-size building blocks imply that, on the whole,
cometary nuclei may be smaller than previously thought.

Comet breakups are far from unusual. For example, another LINEAR discovery,
C/2001 A2 -- currently visible in Southern Hemisphere skies -- recently
broke in half on its approach to the Sun. On May 16th, the 8.2-meter Yepun
reflector of the Very Large Telescope took an image showing that a third
piece has broken off. LINEAR C/2001 A2 reaches its closest point to the Sun
on May 24th. The comet also continues to brighten. Observers report that it
is a naked-eye 5th magnitude, where the comet is about 20 deg. above the
west-southwest horizon after evening twilight. It will not be visible from
the Northern Hemisphere until late June. Here are coordinates for Comet
LINEAR C/2001 A2 at 0 hours Universal Time for the coming week:

R.A. Dec.

May 19 5h 35m -23.4 deg.
May 21 5 31 -24.1
May 23 5 27 -24.8
May 25 5 21 -25.5

A COMET'S LINEAR-AGE

Even before its slow-motion disintegration last year, Comet LINEAR (C/1999
S4) was the crosshairs of many telescopes. Its brightness allowed planetary
scientists to conduct spectroscopic studies that would be impossible on
dimmer passers-by. Curiously, Comet LINEAR proved to be unlike other bright
comets, in that it contained relatively little carbon monoxide (CO) relative
to its water content.

Frozen CO vaporizes even at very cold temperatures, so when seen abundantly
in the comas of Halley, Hale-Bopp, and Hyakutake, astronomers concluded that
these iceballs formed very cold, in the vicinity of Uranus or Neptune,
before being flung out into the distant cometary reservoir known as the Oort
Cloud. This trio of comets also exhibited a high ratio of deuterium to
hydrogen, typical of that found in interstellar clouds of gas. Because the
comets' D-to-H ratio was at least double that found here on Earth, cosmic
chemists began to think that only a fraction of our planet's water could
have been delivered by comets.

However, Comet LINEAR's low CO value implies that it formed somewhat closer
to the Sun's warmth, perhaps near Jupiter, before taking up residence in the
Oort Cloud. As Michael C. Mumma (NASA/Goddard) and his colleagues explain in
today's issue of Science, such comets should have D:H ratios much closer to
that of seawater, which could mean that incoming comets delivered the bulk
of Earth's water after all. "The idea that comets seeded life on Earth with
water and essential molecular building blocks is hotly debated," Mumma
notes, "and for the first time, we have seen a comet with the right
composition to do the job." But his team will have to wait for another
bright comet to test their hypothesis further, because Comet LINEAR's D:H
ratio could not be determined.

Of course, comets weren't the only small bodies that formed near Jupiter.
Asteroids did too, and the most distant ones contain up to 20 percent water.
In 1997, Harold Levison (Southwest Research Institute) and Martin Duncan
(Queen's University) estimated that roughly 8 percent of all the objects
initially present in the outer asteroid belt (3.3. to 5.0 astronomical units
from the Sun) were ejected by Jupiter into the Oort Cloud. Over time, some
of these must boomerang their way back to the inner solar system. Even if
LINEAR wasn't one of them, it's definitely caused a stir among planetary
scientists.

[...]

Copyright 2001 Sky Publishing Corporation. S&T's Weekly News Bulletin and
Sky at a Glance stargazing calendar are provided as a service to the
astronomical community by the editors of SKY & TELESCOPE magazine.
Widespread electronic distribution is encouraged as long as these
paragraphs are included. But the text of the bulletin and calendar may not
be published in any other form without permission from Sky Publishing
(contact permissions@skypub.com or phone 617-864-7360). Updates of
astronomical news, including active links to related Internet resources, are
available via SKY & TELESCOPE's site on the World Wide Web at
http://www.skypub.com/.

===========
FLYBYS: ASTEROIDS 2000 XG47 & 2001 GQ2

From Spaceweather.com, 26 January 2001

Two near-Earth asteroids are passing by our planet on April 27th: 2000 XG47
and 2001 GQ2. Amateur astronomers with 8 inch or better telescopes and CCD
cameras can spot the space rocks as they brighten to ~13th magnitude in the
days ahead. 2000 XG47 (pictured above) is a ~1.5 km object that comes no
closer to Earth than 0.106 AU. 2001 GQ2 is much smaller (only ~300m across)
but it's just as bright as its larger cousin because 2001 GQ2 is nearer to
us  -- only 0.02 AU (about 8 lunar distances) from our planet on Friday.

==========
(6) WILD WIDE UNIVERSE

From The Hindu, 21 May 2001
http://www.indiaserver.com/thehindu/2001/05/21/stories/0421403r.htm

OUTER SPACE is as violent as the earth! Accidents and collisions are
happening all the time by the comets, meteors, and other space objects. And,
when these collide with our planet, they could be devastating.

For hundreds of years, man has feared attacks from beings of other planets
and the prospect of some gigantic object crashing into our atmosphere
endangering life. The dinosaurs, which ruled the planet, are said to have
vapourised into thin air after a giant meteorite or a comet hit the earth.

The Chicxulab crater in Mexico, Lonar lake in Maharashtra, the fireworks in
Siberia in 1908 known as the Tunguska event, meteorite fall in Piplian
Kalan, a village in Rajasthan, are all examples of the objects from the
limitless universe falling into the earth.

These matters and more were quite exhilaratingly presented in the Birla
Planetarium's new sky show - `The Violent Universe', which has been
inaugurated on Saturday with the Union Minister of State for Home, Ch.
Vidyasagar Rao, attending.

With a depiction of the city's night sky, the viewers are transported to the
outerspace beyond the solar system. The planets and the asteroid belt
between Mars and Jupiter from where huge chunks of rocks sometimes hurtle
towards the earth are shown. The `Oort cloud' beyond the orbit of Pluto from
where the comets originate which, too, at times crash into our planet is
projected dramatically.

As the planetarium Director, Dr. B.G. Sidharth, explains, the universe is a
strange place as the collisions and explosions that destroy and kill can
also create and give birth to new celestial objects and perhaps, even life!
Astronomers also believe the comets collision with earth to be responsible
for the origin of life.

But, what happens when a giant rock debris comes in direct conflict with
earth? Can we ward off the danger with our nuclear weapons as shown in
Hollywood flicks? A round-the-clock monitoring service is on in the United
States to look for signals from outer space and also to watch out for such
probable catastrophic collisions.

Certainly, a new treat for the star gazers at the planetarium.

By V. Geetanath

Copyrights © 2001 The Hindu & indiaserver.com, Inc.

==============
(7) COMET C/1999 S4 (LINEAR)

From Comets & Meteor Showers
http://comets.amsmeteors.org/comets/lcomets/1999s4.html

Discovery

This is another comet found by the automatic minor planet search program
LINEAR in New Mexico. It was found on CCD images obtained between 1999
September 27.40 and September 27.45 and was reported as an unusual moving
object. The nuclear magnitude was given as 17.3-17.6. LINEAR obtained
additional images on September 28 and October 1. On October 1.40 and 1.43,
D. T. Durig (Cordell-Lorenz Observatory, Sewanee, Tennessee) obtained images
of the comet with a 0.3-m Schmidt-Cassegrain and a CCD. He noted a total
magnitude of 16.3 on the second image, as well as a coma 10 arcsec across
and a tail extending 20-25 arcsec toward PA 200°-220°. The cometary nature
was confirmed on October 1.89, when J. Ticha and M. Tichy (Klet Observatory)
imaged the comet with a 0.57-m reflector and a CCD. They determined the
total magnitude as 16.2 and noted a coma 8 arcsec across and a tail
extending more than 10 arcsec toward PA 245°.

Historical Highlights

The first published orbit came from Brian G. Marsden (Harvard-Smithsonian
Center for Astrophysics) on October 1. His parabolic solution, based on
observations collected over five days, indicated a perihelion date of 2000
July 18 and a perihelion distance of 0.72 AU. He suggested "this comet might
become a naked-eye object next July." Marsden revised the comet's orbit on
October 6, using positions collected over eight days. The new perihelion
date was 2000 July 24.2 and a perihelion distance of 0.754 AU. His ephemeris
indicated the comet's maximum brightness could reach magnitude 4.

The comet slowly brightened during the months immediately following
discovery. It was slightly fainter than magnitude 14 during November and was
brighter than 14 as 2000 began. The total magnitude had reached 13.5 during
the first week of March, and the comet was lost in the sun's glare after
March 22.

The comet was recovered in the morning sky on May 4, by K. Kadota (Ageo,
Japan) at a magnitude of about 13. Observations by other observers began
around mid-May after the comet had gained more altitude in the morning sky
and had become brighter than magnitude 12. By the beginning of June most
observers were reporting a brightness slightly fainter than magnitude 10,
with a moderately condensed coma about 3 arcmin across. Visual observations
of the tail became fairly common in larger amateur telescopes after
mid-June, with the length typically estimated as 4-5 arcmin. As June came to
a close, most observers found the comet slightly brighter than magnitude
8.5. The coma was then about 5-6 arcmin across and the tail about 10 arcmin
long.

During June, revised predictions of the maximum brightness of this comet
indicated a maximum magnitude of 4 to 6 would be attained around July 22 or
23. Although an apparent change in the rate of brightening occurred on June
22, which indicated the comet was heading for the magnitude 6 prediction, an
minor outburst around July 5 to 6 was indicated by visual observers and
fathered hopes that the comet might still reach magnitude 4 or 5. This
brightening only lasted a few days, however, and by mid-July most observers
were giving in to the possibility that this comet would not become brighter
than magnitude 6. With respect to the brightening in early July, it is
interesting that on July 28, the Space Telescope Science Institute issued
press release giving details of observations made by the Hubble Space
Telescope on July 5, 6, and 7. The images indicate a brief outburst on the
6th and the appearance of a fragment moving toward the tail from the nucleus
on the 7th. Complete details and images can be found at the Hubble Space
Telescope web site.

The comet continued a slow brightening as July progressed. By July 21, the
general consensus was that the comet's brightness was between magnitude 6.6
and 6.8, with a coma 5 to 6 arcmin across and a dust tail 30 to 60 arcmin
long. But something happened late on the 21st and by July 22, observers were
commonly reporting the magnitude as around 6 and, although the coma diameter
and dust tail had not changed, there was a bright, straight, long gas tail.
My personal observations on July 22.16 revealed a brighter comet than I had
seen a couple of days earlier, a a unmistakable, straight gas tail extending
at least 1 degree. This is exactly why people like me observe comets. Their
potential unpredictability makes them very interesting.

So, on July 23 I asked the question "what will happen next?" and noted "The
gas tail seen on the 21st and 22nd was certainly short-lived and indicates
something sudden and violent occurred to the nucleus. It may only prove to
have been a new pocket of gas that was released, but observers should be on
the lookout for something more within the coma during the next few days and
weeks." Well, the comet has indeed undergone changes that became apparent
shortly before July ended. The comet's nuclear region became noticeably more
diffuse and elongated beginning on July 25, and the comet began fading at a
rate much greater than had been predicted. My final observation was made
with my 33.3-cm reflector on August 2 and revealed a slightly elongated
nebulosity with virtually no condensation. My estimate of the comet's
brightness was 9, which was over 2 magnitudes fainter than expected.

The Hubble Space Telescope was used to observe the comet on August 5. What
it found was more than a dozen tiny comets enveloped by a cloud of dust in
the area where comet LINEAR was supposed to be. The image below is only a
small section of the photo. The large scale images and complete story are on
the Hubble web site. Interestingly, the images were obtained at about the
same time as another, wider field image was obtained with the 2.2-meter
telescope at the Mauna Kea observatory complex.

In a display of how good ground-based observations can be, the European
Southern Observatory released an image obtained at Paranal (Chile) with the
8.2-m Very Large Telescope ANTU unit on the evening of August 6. A portion
of the image is shown below. The complete image and press release is located
on the VLT web site.

============================
* LETTERS TO THE MODERATOR *
============================

(8) PYRAMIDS IN THE SKY

From Duncan Steel <D.I.Steel@salford.ac.uk>

Dear Benny,

I note with interest various recent postings that have involved the
(Egyptian) pyramids and their possible connections with solar system
phenomena (as opposed to earlier suggestions made over recent decades of
alignments with more distant celestial objects: stars and so on). Matt Genge
discussed the possible pyramidal shape of meteorites.

Let me turn attention to another solar system phenomenon. If one were to
look up "zodiacal light" in a selection of astronomy dictionaries,  many
entries will be found to begin by saying that this is the "pyramid-shaped
column of light centered on the ecliptic and seen in the east soon before
sunrise or in the west soon after sunset" - or some such statement. (This
was pointed out to me by Howard Jones some years ago.) This phenomenon is
caused by interplanetary dust, concentrated about the ecliptic, which
scatters sunlight. The major contributor is dust in the 10-100 micron size
range. Such dust is produced/liberated by comets, and there is also a
fraction resulting from inter-asteroid collisions.

Although people living in temperate latitudes (especially cities due to the
artificial lights) may not be familiar with the zodiacal light, those living
nearer the tropics will know it well. The pyramid shapes near the horizon
are bright due to the dust (which has a spatial density increasing towards
lesser heliocentric distances) causing efficient forward-scatter of
sunlight. In a particularly dark location someone with excellent eyes may be
able to see the zodiacal band: a thin band of light following the ecliptic
across the night sky. This brightens as the solar opposition point is
reached, due to the increased efficiency of direct backscatter (similarly
the full moon is typically nine times as bright as the Moon at first or last
quarter, not merely twice as bright). This dust-scattered light near
opposition is called the 'gegenschein' (counter glow). I believe that I
would be correct to say that fully 40% of the total light in the moonless
sky is due to scatter by interplanetary dust.

That, though, is the situation at present. Although one could suggest that
if the pharoahic Egyptians were mimicking something celestial with their
pyramids, the present zodiacal light is impressive enough. However, there is
no compelling reason to suppose that what they saw 4,800 years ago is the
same as what we see now. The lifetimes of interplanetary dust grains are
measured only on timescales of 10^3-10^4 years on various dynamical grounds,
plus collisional lifetime calculations, and ip dust collected in the
stratosphere display cosmic ray track ages indicative of this short time
scale. A recent paper by Bill Napier that was mentioned in CCNet has shown
how the interplanetary dust population may be expected to display radical
departures from any long-term (10^5-10^6 year) average.

The pyramidal zodiacal light might therefore have been much brighter in the
past. Similarly the zodiacal band would have been much brighter. In the past
astronomers/archaeologists have connected the ancient Egyptian allusions to
a "river in the sky" (a celestial analogue of the Nile) with the broad sweep
of the Milky Way. I would suggest that perhaps a much more prominent
zodiacal band is what they were talking about, especially if it were
changing its characteristics and brightness.

If a very bright and active comet were responsible for a major but temporary
dust population boost, as recently modelled by Napier (and previously
discussed in various publications by him and the usual suspects: Asher,
Bailey, Clube, Steel), then an immediate product through which much of the
eventual small dust would stem is a massive meteoroid stream. (Here
"meteoroid" denotes a particle larger than 100 microns and thus not "dust";
that size is the approximate micrometeorite limit, with smaller particles
slowing down in the atmosphere without ablating, whereas larger ones produce
"meteors" and so sublimate away to virtually nothing.) That meteoroid
stream, if it had a perihelion distance of less than 1 AU, would intersect
the Earth at least once per year in various multi-century episodes,
connected with its precession under secular perturbations. When an
intersection occurs, phenomenal meteor showers/storms would occur. The
meteor trains during such storms produce another celetial effect like a
pyramid, within which the viewer is enclosed; the shower radiant is the apex
of the pyramid.

A final couple note. Pyramids of various designs are found elsewhere, not
just in Egypt. Of course they are of different ages, but it might be noted
that in general they are located within the tropics. The tropics are the
places where the zodiacal light is most obvious, and also where it spends
more of the year appearing as a vertical pyramid (as opposed to the slope of
the ecliptic on the horizon for most of the year at higher latitudes).

Just a few things to chew on.

Duncan Steel

===========
(9) SHAPE OF PYRAMIDS

From Rolf Sinclair <rolf@santafe.edu>

Hi Benny --

Regarding the shape of pyramids (CCNet 69/2001 - 18 May 2001): Kurt
Mendelssohn, in "The Riddle of the Pyramids" (1974), made a simple
suggestion, that the shape of the pyramids was inspired by a common pattern
of rays of sunlight, angling down to the left and right when the sun itself
was obscured by a cloud. He also argued that this shape was developed by
trial and error, the
process involving one pyramid that collapsed while partly built. His book
developed the important role that the social organization necessary for the
pyramid construction enterprise would have played in the development of the
Egyptian state, and through this explained a number of features of the
pyramids.

Rolf

==========
(10) IMPACTS & HUMAN EVOLUTION

From Worth Crouch <doagain@jps.net>

Dear Dr. Peiser:

I have been reading considerable criticism in the CCNet about your
forthcoming collaborative paper IMPACTS & HUMAN EVOLUTION. Although some of
the criticism has merit I think much of it is trivial, because it doesn't
address the essence of the arguments found in your paper.

As I understand IMPACTS & HUMAN EVOLUTION there is an attempt to point out
that during the last five million years of human evolution our planet has
been bombarded by cosmic (asteroid/comet) collisions. The collisions were of
various numbers, at various places, and through a distribution of various
magnitudes. There is an attempt to quantify the numbers, places, and
magnitudes and an analysis of their potential consequence on human evolution
is presented. Furthermore, the numbers, places, and magnitudes of the
collisions written about are not inconsequential; therefore some consequence
on human evolution should be easily understood without much argument, some
arguable, and some never to be known. A few possible consequences are:

* Due to the dispersion of humanoids our ancestors survived direct
impacts.
* Various humanoids possibly became extinct, because they failed to
adapt as well as our ancestors to environmental conditions following
cosmic impacts.
* Volcanism, earthquakes, and fires following impacts encouraged our
ancestors to increase their adventure onto the plains or at least to the
periphery of the woodlands to avoid forest fires and competition for
diminishing forest resources.
* Thus, bipedal mobility would be encouraged along with upright
posture. Moreover, our ancestors would have an advantage, because their
hands would become increasingly free to make better tools than other
humanoids; consequently the evolution of the human thumb could take place.
* Furthermore, our ancestors would have had an advantage if sunlight
were reduced due to dust in the upper atmosphere resulting from
cosmic impacts. Those that could better make fire, fashion garments,
and develop warmer places to live would have a better chance to survive
and reproduce.
* During times, which resulted from cosmic impacts, when stress was
placed on humanoids to provide food, our ancestors had an advantage. Those
that had language would be more fit to hunt, garden, and gather food
because they could work in specialty teams better than those without
language communication.

Some of this means that intelligence was a survival strategy that our
ancestors incorporated through evolution to perpetuate themselves and
advance the species through stressful times.

I suppose I could go on for quite a while explaining how some stress, but
not too mush, could advance the evolutionary process of our ancestors, but
this is well understood by most biologists, geologists, and paleontologists.
The simple point of IMPACTS & HUMAN EVOLUTION is that cosmic impacts
provided environmental stress from outer space that could advance human
evolution and probably speed it up a bit. I don't think any good scientists
would discount the importance of IMPACTS & HUMAN EVOLUTION if in fact the
impacts altered the environment so that increasing stress was placed on our
evolving ancestors; thus causing them to adapt and advance so our species
could evolve. Moreover, after examining the devastation of the small 1908
cosmic impact in Siberia it would be very hard to believe the impacts
described in IMPACTS & HUMAN EVOLUTION would not stress the nearby humanoid
populations into even more adaptations, or extinctions, than I have
described.

Worth F. Crouch
(Talako)
Choctaw Society of Astrobiologists

=============
* ABSTRACTS *
=============

(11) MORE OBSERVATIONS OF SHOEMAKER-LEVY 9 IMPACT

de Pater I, Brecht SH: SL9 impacts: VLA high-resolution observations at
lambda=20 cm
ICARUS 151 (1): 1-24 MAY 2001

We present high resolution (0.3 R-J) VLA observations of Jupiter at a
wavelength of 20 cm which were taken during and after the impacts of Comet
D/Shoemaker-Levy 9. The observations are presented both as a function of
central meridian longitude lambda (cml) and, after applying tomographic
techniques, as a function of jovicentric longitude lambda (III) Following an
impact all radiation peaks (both the main and high latitude emission peaks)
usually shift inward, toward the planet, and brighten up; the first impact,
however, triggered a decrease rather than an increase in the intensity of
the radiation peaks. Although the high latitude regions always brighten,
they do not brighten up as much as the main radiation peaks during the first
few days of the impacts, whereas they brighten up significantly more than
the main radiation peaks later in the impact week. The high latitude
regions, in particular in the southern hemisphere, move slightly closer to
the magnetic equator. (C) 2001 Academic Press.

Addresses:
de Pater I, Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley,
CA 94720 USA
Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA
Bay Area Res Corp, Orinda, CA 94563 USA

Copyright © 2001 Institute for Scientific Information

============
(12) MODIFICATION OF THE JOVIAN RADIATION BELT BY SHOEMAKER-LEVY 9

Brecht SH, de Pater I, Larson DJ, Pesses ME: Modification of the Jovian
radiation belts by Shoemaker-Levy 9: An explanation of the data
ICARUS 151 (1): 25-38 MAY 2001

The SL9 impacts provided a unique data set with which to examine some
surprising physical mechanisms at work. This paper examines some of the data
in light of the collisionless shock acceleration paradigm, called diffusive
shock acceleration. The research finds that both the shock acceleration
mechanism and an enhanced diffusion mechanism are required to explain the
data. Direct numerical simulations and analytic models are used to compare
these mechanisms with the data collected. The results are consistent with
the data. In addition further analysis of these SL9 VLA data strongly
suggests that for periods of days the relativistic radiation belts drift in
a direction opposite to that predicted by normal drift theory. (C) 2001
Academic Press.

Addresses:
Brecht SH, Bay Area Res Corp, POB 366, Orinda, CA 94563 USA
Bay Area Res Corp, Orinda, CA 94563 USA
Univ Calif Berkeley, Berkeley, CA 94720 USA
Sci Applicat Int Corp, Mclean, VA 22102 USA

Copyright © 2001 Institute for Scientific Information

============
(13) THE SHOEMAKER-LEVY 9 IMPACT & ENHANCED RADIAL DIFFUSION

de Pater I, Brecht SH: SL9 impacts and simulations of enhanced radial
diffusion
ICARUS 151 (1): 39-50 MAY 2001

We present detailed calculations on enhanced radial diffusion models and
show that many, though not all, of the phenomena observed during the week
that Comet Shoemaker-Levy 9 crashed into Jupiter can be explained by a
sudden increase in the radial diffusion coefficient. Our calculations use
estimates for the enhancement in the diffusion coefficient which come from
self-consistent calculations of the electromagnetic turbulence generated by
the impacts (Brecht er al. 2001, Icarus). These calculations suggest that
the diffusion coefficient is enhanced at least a few million times above the
nominal value during a short period of time (minutes). Our model shows that
Jupiter's main radiation peaks brighten up much more than the high latitude
regions, as is indeed observed following impacts during the first few days
of the impact week. The calculations also suggest that the largest
enhancements in intensity and largest inward shift of the radiation peaks
occur at jovicentric longitudes similar to 100 degrees less than or similar
to lambda (III) less than or similar to 250 degrees, i.e., the longitude
range where the B = constant contours are furthest from the planet. This
longitude range agrees with the region where the strongest enhancements have
indeed been observed. The dramatic increase in the intensity of the high
latitude peaks following impacts which took place later in the week is
attributed to a direct acceleration of electrons by the upward propagating
shock. Finally, compared to the observations, the radial diffusion models
predict much larger enhancements in the radiation peaks than observed. We
attribute this, as well as the initial decrease in intensity on July 16-17,
to a large loss of electrons caused by pitch angle scattering. (C) 2001
Academic Press.

Addresses:
de Pater I, Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley,
CA 94720 USA
Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA
Bay Area Res Corp, Orinda, CA 94563 USA

Copyright © 2001 Institute for Scientific Information

==========
(14) FORCED PRECESSION MODELS FOR SIX ERRATIC COMETS

Krolikowska M, Sitarski G, Szutowicz S: Forced precession models for six
erratic comets
ASTRONOMY AND ASTROPHYSICS 368 (2): 676-688 MAR 2001

The nongravitational motion of six "erratic" short-period comets is studied
on the basis of published astrometric observations. We present the
precession models which successfully link all the observed apparitions of
the comets: 16P/Brooks 2, 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2,
32P/Comas Sola, 37P/Forbes and 43P/Wolf-Harrington. We used the Sekanina's
forced precession model of the rotating cometary nucleus to include the
nongravitational terms into equations of the comet's motion. Values of six
basic parameters (four connected with the rotating comet nucleus and two
describing the precession of spin-axis of the nucleus) have been determined
along the orbital elements from positional observations of the comets. The
solutions were derived with additional assumptions which introduce
instantaneous changes of modulus of reactive force, and of maximum cometary
activity with respect to perihelion time. The present precession models
impose some constraints on sizes and rotational periods of cometary nuclei.
According to our solutions the nucleus of 21P/Giacobini-Zinner with
oblateness along the spin-axis of about 0.29 (equatorial to polar radius of
1.41) is the most oblate among six investigated comets.

Addresses:
Krolikowska M, Polish Acad Sci, Space Res Ctr, Bartycka 18A, PL-00716
Warsaw, Poland
Polish Acad Sci, Space Res Ctr, PL-00716 Warsaw, Poland
Univ Bialystok, Inst Theoret Phys, PL-15424 Bialystok, Poland

Copyright © 2001 Institute for Scientific Information

=========
(15) THE ORBIT EVOLUTION OF 32 PLUTINOS OVER 100 MILLION YEARS

Wan XS, Huang TY: The orbit evolution of 32 plutinos over 100 million year
ASTRONOMY AND ASTROPHYSICS 368 (2): 700-705 MAR 2001

The orbits of thirty two plutinos that are presently in the 3:2 mean motion
resonance with Neptune have been integrated numerically and accurately to
10(8) years into the future. Fourteen of them are found in unstable orbits
after encountering Neptune or Pluto. Six of eighteen plutinos with stable
orbits are in the Kozai resonance or around its separatrix zone. No node to
node, perihelion to perihelion secular resonance or the so called 1:1 super
resonance are found.

Addresses:
Huang TY, Nanjing Univ, Dept Astron, Nanjing 210093, Peoples R China
Nanjing Univ, Dept Astron, Nanjing 210093, Peoples R China
Natl Astron Observ, Beijing, Peoples R China

Copyright © 2001 Institute for Scientific Information

=============
(16) THE CHEMISTRY OF INTERSTELLAR SPACE

Herbst E: The chemistry of interstellar space
CHEMICAL SOCIETY REVIEWS 30 (3): 168-176 MAY 2001

Interstellar space is not empty, but contains gaseous and particulate matter
that is concentrated into very large regions known as interstellar clouds.
In the denser and cooler clouds, the gas is molecular and most of the
molecules detected are organic in nature. The gas-phase molecules are
synthesised from precursor atoms by rapid exothermic reactions in the gas
and on the surfaces of tiny dust particles. Since dense interstellar clouds
collapse to form stars and planetary systems, the molecules produced in the
clouds may be eventually incorporated into solid bodies such as comets,
meteors, and even planets.

Addresses:
Herbst E, Ohio State Univ, Dept Phys & Astron, Columbus, OH 43210 USA
Ohio State Univ, Dept Phys & Astron, Columbus, OH 43210 USA

Copyright © 2001 Institute for Scientific Information

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