PLEASE NOTE:
*
CCNet DIGEST, 30 April 1998
---------------------------
(1) NEWS ARTICLE ABOUT IMPACT THREAT
Phil Burns <pib@nwu.edu>
(2) THREAT OF ASTEROIDS: TOO CLOSE FOR COMFORT
http://www.abcnews.com/sections/science/DailyNews/asteroid980429.html
(3) GIACOBINIDS IN 1998
Don Yeomans <dyeomans@mail1.jpl.nasa.gov>
(4) SIMULATING ATMOSPHERIC ENTRY HEATING OF MICRO-METEOROIDS
A. Greshake et al., Humboldt University,
Berlin
(5) NONGRAVITAIONAL EFFECTS IN COMET MOTION
G. Michalak, Wroclaw University Observatory,
Poland
(6) NONGRAVITATIONAL MOTION IN THREE SHORT-PERIOD COMETS
M. Krolikowska et al., Polish Academy of
Science
(7) MUSINGS ON FULMINE
Ed Grondine <epgrondine@hotmail.com>
=====================================
(1) NEWS ARTICLE ABOUT IMPACT THREAT
From Phil Burns <pib@nwu.edu>
Today (April 29, 1998) many news media here in the U. S. carried
an
article from the Scripps Howard News Service written by Lawrence
Spohn.
You can find a copy online at
http://www.abcnews.com/sections/science/DailyNews/asteroid980429.html
The article, which quotes Mark Boslough, Eleanor Helin, Grant
Stokes,
and Alan Hale, reemphasizes the difficulties faced in obtaining
funding
for programs to search for potentially hazardous objects.
-- Phil "Pib" Burns
Northwestern University, Evanston, IL. USA
pib@nwu.edu
http://pibweb.it.nwu.edu/~pib/
====================
(2) THREAT OF ASTEROIDS: TOO CLOSE FOR COMFORT
By Lawrence Spohn
Scripps Howard News Service
Albuquerque, New Mexico, April 29 —
Asteroid trackers say the government may be getting serious about
the
real threat of an asteroid or comet with Earth's name on it.
They reported serious discussions between NASA and the Air Force
to
collaborate on identifying any nearby cosmic nemesis that might
be on a
collision course with Earth.
But they'll believe it, they said, when they see the government
money
and expanded programs necessary to effectively search the heavens
for
"near-Earth objects" that have the potential to
devastate life on the
Blue Orb.
Among nearly 400 space scientists and engineers attending Space
'98 and
Robotics '98 conferences in Albuquerque this week, they said they
already have found dozens of PHOs, or "potentially hazardous
objects,"
whose orbits someday will bring them too close to Earth for
comfort.
The threat is real even if it may seem improbable and distant,
said
Mark Boslough, a scientist at Sandia National Laboratories in
Albuquerque.
MORE TELESCOPES
Boslough accurately predicted that a series of comet impacts on
Jupiter
four years ago would have the explosive force of more than all of
the
world's nuclear bombs. The impacts were so extreme they sent
Jovian
debris streaming into space and caused lasting atmospheric
changes on
the giant planet's face.
But without additional government funding, it will take decades
to find
all the dim space wanderers that could pose an Earthly threat,
said
Eleanor Helin, who directs the Near Earth Asteroid Tracking
program at
the National Air and Space Administration's Jet Propulsion
Laboratory
in Pasadena, Calif.
The program uses an Air Force Research Laboratory satellite
tracking
telescope in Hawaii that has advanced technology developed and
tested
at the Air Force's Starfire Optical Range at Kirtland Air Force
Base in
Albuquerque.
But the Jet Propulsion Laboratory program gets only six nights a
month
to make asteroid searches with the Hawaii telescope. Noting that
her
program alone has identified 118 threatening asteroids among
12,025 new
ones it has identified in the last few years, Helin said the
program
needs to be tripled.
It should include two additional telescopes and at least 18
nights of
observations, she said. At that rate, she believes astronomers
could
identify 90 percent of the threats within 15 years.
"We're operating on a beg, borrow or steal basis, like
everybody else
in this business," said Grant Stokes, of the LINEAR Space
Surveillance
program at the Massachusetts Institute of Technology.
NASA, AIR FORCE TALKING
It is using sophisticated, light-sensitive electronics, developed
by
MIT for the Air Force, in a meticulous sky search that in March
alone
found 13 new near-Earth objects and one comet.
"They're letting us do it, but we're Air Force-funded and
-controlled,"
Stokes said. He said he has been told that an Air Force general
in
Colorado Springs, Colo., and NASA administrator Dan Goldin have
begun
discussions on how to collaborate on a formal, united near-Earth
search
using civilian and military resources.
New Mexico astronomer Alan Hale, who co-discovered one of the
most
spectacular comets ever seen, Comet Hale-Bopp, suggested
government
officials may sense that the issue may be "capturing the
public's
fancy."
HOLLYWOOD WEIGHS IN
He said two movies about cosmic collisions with Earth are due to
open,
Deep Impact this weekend and Armageddon this summer.
Deep Impact is based on Los Alamos National Laboratory scientist
Jack
Hills' research that predicts a large comet or asteroid impact in
one
of the major oceans would cause massive tidal waves that would
swamp
coastal cities. The largest impact could send a wave surge as far
inland as the Midwest, some scientists have calculated.
The Sandia and Los Alamos national laboratories are
nuclear-weapons
labs, and some weaponeers believe warheads could be used to
deflect or
destroy a threatening asteroid or comet.
Boslough said scientists have plenty of evidence that potentially
catastrophic collisions occur about once a century, but the
ultimate
damage depends on where on Earth the object strikes and how big
it is.
Even small objects that never reach the surface but detonate in
the
atmosphere can explode with the force of a nuclear bomb, Boslough
said,
citing the Tunguska event in Siberia early this century.
The shock wave and heat can threaten life directly or indirectly
through fire storms, he said.
Scientists believe the evidence is compelling that a killer comet
struck Earth 65 million years ago and caused the extinction of
the
dinosaurs possibly through global climate change from
sun-shielding
debris spewed in the atmosphere.
Copyright 1998 Scripps Howard News Service
===============================
(3) GIACOBINIDS IN 1998
From Don Yeomans <dyeomans@mail1.jpl.nasa.gov>
Hi Duncan,
With regard to you recent remarks in Benny's CC forum, you may be
interested in the following table. If history is any guide, the
Giacobinids will not be very impressive this year since the Earth
arrives at the comet's descending node before the comet passes
through
this position and the distance between the comet and Earth orbits
near
the comet's descending node are relatively large. I'd say that
Oct. 9,
2018 looks pretty good for the next significant Giacobinid
shower.
However, when it comes to meteor showers, there are always
surprises
and it would certainly be a good idea to look for Giacobinid
activity
in Oct. of this year.
With kind regards,
Don
Giacobinid Meteor Shower Circumstances (1926 - 2031)
Year C-E (AU) q (AU) Earth
at Shower
Max. Radiant
Desc. Node (Oct.)
ZHR (Deg.)
1926 -0.0005 0.99373 69.1
before 9.981 17
1933 +0.0054 0.99953 80.2
after 9.767 5000
1946 +0.0015 0.99571 15.4
after 10.157 5000
1952 -0.0057 0.98869 195.5 before
9.648 180
1985 +0.0329 1.02826 27.2
after 8.549 700?
1992 +0.039 1.0340 172.0
after
8.32
260.58 +57.39
1998 +0.038 1.0337 49.5
before
8.87
260.62 +57.42
2005 +0.043 1.0379 91.8
after
8.70
260.52 57.54
2012 +0.035 1.0305 131.7
before
9.20
260.78 57.36
2018 +0.017 1.0127 22.7
after
9.00
261.64 56.78
2025 +0.013 1.0089 174.2
before
8.47
261.81 56.71
2031 +0.076 1.0692 29.6
after
8.37
256.91 58.34
The column entries are:
Year of Giacobinid Shower (or potential shower)
C-E: The distance (in AU) between the comet's and Earth's
orbit at
the comet's descending node.
q: Comet's perihelion distance (in AU)
Earth at Descending node: The number of days before or
after
the comet that the Earth arrives at the comet's descending node.
The date the Earth arrives at the comet's descending node or
the time of the predicted shower maximum.
ZHR: Approximate, observed zenith hourly rate
Radiant: Predicted RA and DEC of shower (in deg., J2000).
Donald K. Yeomans - JPL
==========================
(4) SIMULATING ATMOSPHERIC ENTRY HEATING OF MICRO-METEOROIDS
A. Greshake*), W. Klock, P. Arndt, M. Maetz, G.J. Flynn, S. Bajt,
A.
Bischoff: Heating experiments simulating atmospheric entry
heating of
micrometeorites: Clues to their parent body sources. METEORITICS
&
PLANETARY SCIENCE, 1998, Vol.33, No.2, pp.267-290
*) HUMBOLDT UNIVERSITY, INSTITUT FUER MINERALOGIE, MUSEUM
FUER NATURKUNDE, INVALIDENSTR 43, D-10115
BERLIN,GERMANY
Depending on their velocity, entry angle and mass,
extraterrestrial
dust particles suffer certain degrees of heating during entry
into
Earth's atmosphere, and the mineralogy and chemical composition
of
these dust particles are significantly changed. In the present
study,
pulse-heating experiments simulating the atmospheric entry
heating of
micrometeoroids were carried out in order to understand the
mineralogical and chemical changes quantitatively as well as to
estimate the peak temperature experienced by the particles during
entry
heating. Fragments of the CI chondrites Orgueil and Alais as well
as
pyrrhotites from Orgueil were used as analogue material. The
experiments show that the volatile elements S, Zn, Ga, Ge, and Se
can
be lost from 50 to 100 mu m sized CI meteorite fragments at
temperatures and heating times applicable to the entry heating of
similar sized cosmic dust particles. It is concluded that
depletions of
these elements relative to CI as observed in micrometeorites are
mainly
caused by atmospheric entry heating. Besides explaining the
element
abundances in micrometeorites, the experimentally obtained
release
patterns can also be used as indicators to estimate the peak
heating of
dust particles during entry. Using the abundances of Zn and Ge
and
assuming their original concentrations close to CI, a maximum
heating
of 1100-1200 degrees C is obtained for previously analyzed
Antarctic
micrometeroites. Thermal alteration also strongly influenced the
mineralogy of the meteorite fragments. While the unheated samples
mainly consisted of phyliosilicates, these phases almost
completely
transformed into olivine and pyroxene in the fragments heated to
greater than or equal to 800 degrees C. Therefore, dust particles
that
still contain hydrous minerals were probably never heated to
temperatures greater than or equal to 800 degrees C in the
atmosphere.
During continued heating, the grain size of the newly formed
silicates
increased and the composition of the olivines equilibrated.
Applying
these results quantitatively to Antarctic micrometeorites,
typical peak
temperatures in the range of 1100-1200 degrees C during
atmospheric
entry heating are deduced. This temperature range corresponds to
the
one obtained from the volatile element concentrations measured in
these
micrometeorites and points to an asteroidal origin of the
particles.
Copyright 1998, Institute for Scientific Information Inc.
=========================
(5) NONGRAVITAIONAL EFFECTS IN COMET MOTION
G. Michalak: The orbit of the comet 1914 II Kritzinger.
Nongravitational effects in the comet motion. ACTA ASTRONOMICA,
1998,
Vol.48, No.1, pp.103-112
WROCLAW UNIVERSITY OBSERVATORY, KOPERNIKA 11, PL-51622 WROCLAW,
POLAND
Using all available observations of the one-apparition comet 1914
II
Kritzinger we show that the gravitational solution makes (O - C)
residuals non-randomly distributed. We therefore apply three
other
models of the comet motion: (i) with a displacement of the
photometric
center from the center of mass of the comet along the radius
vector,
(ii) with a change in the velocity vector due to a single
outburst of
the comet, and (iii) with Marsden's standard nongravitational
parameters A(1), A(2), A(3). It turns out that models (ii) and
(iii)
fit the observations of comet 1914 II Kritzinger equally well and
give
the same mean residual and the same (O - C) residual
distributions. In
consequence, from the quality of the fit we are not able to
distinguish
which of the two models is better. It is suspected that for some
comets
undergoing an outburst, the model (ii) can be an alternative to,
usually applied, Marsden's model (iii). Copyright 1998, Institute
for
Scientific Information Inc.
=====================
(6) NONGRAVITATIONAL MOTION IN THREE SHORT-PERIOD COMETS
M. Krolikowska, G. Sitarski, S. Szutowicz: Forced precession
model for
three periodic comets: 30P/Reinmuth 1, 37P/Forbes, and
43P/Wolf-Harrington. ACTA ASTRONOMICA, 1998, Vol.48, No.1,
pp.91-102
*) POLISH ACADEMY OF SCIENCE, SPACE RESEARCH CENTRE, BARTYCKA
18A,
PL-00716 WARSAW,POLAND
The nongravitational motion of three short-period comets -
discovered
in the twenties and running on similar heliocentric orbits - has
been
investigated. 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 precessional
parameters:
A, eta, I, phi, f(p) and s have been determined along with
corrections
to orbital elements from astrometric observations of the comets.
We
were able to link successfully all the observations of each comet
over
interval of time spanning about seventy years. According to our
solutions, the nucleus of comet Reinmuth 1 is oblate whereas
those of
comets Forbes and Wolf-Harrington are prolate along the
spin-axis.
Copyright 1998, Institute for Scientific Information Inc.
==========================
(7) MUSINGS ON FULMINE
From Ed Grondine epgrondine@hotmail.com
Benny -
Amazing what a couple of million dollars worth of television
advertising for "Deep Impact" has done. The following
was accepted by
the moderator of the Ancien-L list without so much as a hiccup.
MUSINGS ON FULMINE
Hello -
The Latin word "fulmine" has usually been translated as
"lightening",
but I am beginning to think that this translation has not always
been
correct.
In his landmark work "Linguistica Tyrrhenica" Fred C.
Woudhuizen
establishes the morphological chain pulum (stars) > fulum
(stars) in
Etruscan (pages 48 and 75). Since lightening does indeed come
from the
skies, this might be the end of it, but...
Pliny, writing on lightening in his Natural History, Book II,
Chapter
LIII relates: "Tuscany believes that some also burst out of
the ground,
which it calls "low bolts", and that these are rendered
exceptionally
direful and accursed by the season of winter, though all the
bolts that
they believe of earthly origin are not the ordinary ones and do
not
come from the stars but from the nearer and more disordered
element; a
clear proof of this being that all those coming from upper heaven
deliver slanting blows, whereas these which they call earthly
strike
straight."
To restate this, the Etruscans have two types of fulmine, one
earthly
and another from the stars. What are these "fulmine"
from the stars?
I think that these fulmine may have included exploding
meteorites,
known technically as bolides. What may be even more significant
is that
in the same passage Pliny also relates that Bolsena was
completely
burned up by a fulmine. Now while a lightening strike may set a
few
buildings on fire, we know for certain that a bolide such as the
one
that exploded over Tel Leilan in Syria can reduce a town to a
soil
layer.
This may seem quite a stretch, but consider the following passage
from
Lucretius on meteorites: "it is a fruitless task to unroll
the Tuscan
scrolls, seeking some revelation of the gods' hidden purpose. ...
If it
is really Jupiter and the other gods who rock the flashing frame
of
heaven, why ... Lastly, why does he demolish the holy shrines of
the
gods and his own splendid abodes with a devastating bolt?"
Bolsena
(Volsinii) was the ceremonial center for a league of Etrucan
cities and
as such would have the temple of Jupiter. This appears to
be the same
event related by Pliny.
What happened next along the River Tiber? To the north, the king
of
Clusium attempts to take control of the federation. To the south,
Tarquinius Superbus builds a new home for Jupiter, but the
enslaved
local population revolts, and the rest, as they say, is
history...
Just some musings, and I hope I have not distracted you to much
from your exams. Perhaps you may have at hand other materials
bearing
on this?
Salve -
E.P. Grondine
end of ancien-l list posting
The more astronomically inclined members of the CCNet might find
it of
interest that in Book II, Chapter XXX Pliny also gives pretty
well dated
occurences of "three suns" and "three moons"
- these sound a lot like
atmospheric "skip" incidents to me. Even more alarming,
Pliny also
records the occurence at the time of the 107th Olympiad of
"chasma", an
opening of the sky of a bloody type, "quo nihil terribilis
mortalium
timori est": fire falls from it to the earth. All in
all, Pliny has
passed on to us a very nice collection of reports.
Best Wishes -
Ed
----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
The CCNet is a scholarly electronic network. To subscribe, please
contact the moderator Benny J Peiser at b.j.peiser@livjm.ac.uk.
Information circulated on this network is for scholarly and
educational use only. The attached information may not be copied
or
reproduced for any other purposes without prior permission of the
copyright holders.