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(meteorobs) Excerpts from "CCNet, 8 October 1999"
This issue is packed with interesting meteor items!
Lew
------- Forwarded Message
From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: CCNet, 8 October 1999
Date: Fri, 8 Oct 1999 11:32:59 -0400 (EDT)
CCNet, 8 October 1999
=====================
[...]
(3) IS PLUTO A KUIPER BELT OBJECT AFTER ALL?
SpaceDaily, 6 October 1999
[...]
(9) COMETS & COMMUNICATION - AMATEURS vs PROFESSIONALS
W. Orchiston, NATIONAL OBSERVATORY OF NEW ZEALAND
(10) TV OBSERVATION OF THE 1098 LEONID METEOR SHOWER
J. Watanabe et al., NATIONAL ASTRONONOMICAL OBSERVATORY
(11) THE LEONID METEOR STORMS OF 1833 and 1966
D.J. Asher, ARMAGH OBSERVATORY
[...]
(13) METEOR STORM FORECASTING
I. Ferrin, UNIVERSITY OF LOS ANDES
(14) TRAJECTORY & ORBIT OF THE TUNGUSKA METEORITE REVISITED
V.A. Bronshten, VARSHAVSKOYE RD 16-130,MOSCOW 113105,RUSSIA
(15) SIMULATION OF PROCESSES ON COMET NUCLEI
D.W.G. Sears et al, UNIVERSITY OF ARKANSAS
(16) WEAK RESONANCES DRIVE ASTEROIDS TOWARD TERRESTRIAL=20
PLANETS ORBITS
A. Morbidelli, D. Nesvorny, COTE AZUR OBSERVATORY
[...]
(18) INTERPLANETARY DUST AS FLUFFY AGGREGATES
R. Nakamura & H. Okamoto, KOBE UNIVERSITY
==========================================
(3) IS PLUTO A KUIPER BELT OBJECT AFTER ALL?
>From SpaceDaily, 6 October 1999
http://www.spacedaily.com/spacecast/news/pluto-99c.html
Possible Pluto Debris Spotted
Boulder - October 6, 1999 - Planetary astronomers working in the Space=20
Studies Department (Boulder) of San Antonio-based Southwest Research=20
Institute (SwRI) suggest that some Kuiper Belt objects (KBOs) may be=20
leftover shards from the giant collision that created the Pluto-Charon=20
system.
Pluto-Charon is the only known double planet in the solar system,=20
orbiting about 40 times as far away from the Sun as Earth. It is=20
embedded in the Kuiper Belt of planetesimals, comets, and miniature icy =
worlds that surround our planetary system in a thick disk. The Kuiper=20
Belt is a larger and more populous, icy-rich analog to its better known =
cousin, the Asteroid Belt of rocky debris orbiting between Mars and=20
Jupiter.
Astronomers have suspected for more than a decade that Pluto and its=20
1200 km-wide satellite, Charon, formed as a pair during a giant=20
collision in the ancient past between proto-Pluto and another Kuiper=20
Belt object. Evidence for this collision includes the orbital=20
configuration, the relative masses, and the angular momentum of the=20
Pluto-Charon system.
Now, SwRI astronomers Drs. Alan Stern, Robin Canup, and Daniel Durda=20
have found clues that some KBOs in neighboring orbits to Pluto may, in=20
fact, be debris created in the Pluto-Charon forming event. Their=20
results are being presented Tuesday, October 12, at the American=20
Astronomical Society's (AAS) Division for Planetary Sciences meeting in =
Padua, Italy.
The evidence found by the SwRI team linking some KBOs called "Plutinos" =
to Pluto-Charon comes in three forms. First, there is a close orbital=20
similarity between some KBOs and Pluto that is consistent with the=20
expected distribution of debris from the Pluto-Charon formation event.=20
Second, the colors of Pluto and some KBOs, and Charon and other KBOs,=20
suggest similar surface compositions. Third, the apparent size=20
distribution of the objects that suggest themselves as potential shards =
of the Pluto-Charon forming collision is similar to both laboratory=20
results from studies of catastrophic collisions and asteroid belt=20
families known to result from collisions.
Future research will be required to prove this new hypothesis, dubbed=20
"Pluto's Family." If borne out by future tests, it would constitute the =
first discovery of a genetically related, parent-daughter family of=20
objects in the Kuiper Belt. Further, because the KBO region surrounding =
Pluto has been known for some time to be delivering some comets to=20
Earth's vicinity, the new work suggests that a small, but nonetheless=20
important, fraction of the comets observed by astronomers may actually=20
consist of samples of Pluto and Charon.
SwRI is an independent, nonprofit, applied engineering and physical=20
sciences research and development organization with a staff of 2,700=20
and an annual research volume of $304 million.
Copyright 1999, SpaceDaily
============================================================
(9) COMETS & COMMUNICATION - AMATEURS vs PROFESSIONALS
W. Orchiston: Comets and communication: Amateur-professional tension=20
in Australian astronomy. PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF=20
AUSTRALIA, 1999, Vol.16, No.2, pp.212-221
*) NATIONAL OBSERVATORY OF NEW ZEALAND,CARTER OBSERV, POB 2909,=20
WELLINGTON,NEW ZEALAND
Australasian amateur astronomers, Grigg and Ross, discovered four=20
different comets between 1902 and 1907. Controversy surrounding these=20
discoveries led to a deterioration in relations between Australia's=20
leading amateur astronomers and Baracchi at Melbourne Observatory,=20
and to the eventual transfer of the 'Australian Central Bureau' to=20
Sydney Observatory. Copyright 1999, Institute for Scientific=20
Information Inc.
============================================================
(10) TV OBSERVATION OF THE 1098 LEONID METEOR SHOWER
[Wow! I didn't know they had TVs in the Middle Ages!]
J. Watanabe*), S. Abe, H. Fukushima, D. Kinoshita: TV observation of=20
the Leonid meteor shower in 1998: No strong activity over Japan. =
PUBLICATIONS=20
OF THE ASTRONOMICAL SOCIETY OF JAPAN, 1999, Vol.51,=20
No.4, pp.L11-L14
*) NATIONAL ASTRONONOMICAL OBSERVATORY,MITAKA,TOKYO 1818588,JAPAN
We carried out a high-sensitivity TV observation of the Leonid meteor=20
shower at the Nobeyama Radio Observatory, from 15h20m UT through=20
20h24m UT on 1998 November 17. We detected 58 Leonid meteors, along=20
with 99 sporadic meteors. The peak of the activity, as expected=20
around 20h UT; was not clearly observed. The average influx rate of=20
meteoroids was 1.4 x 10(-5) km(-2) s(-1) (mag less than or equal to=20
+8) during our observation. Copyright 1999, Institute for Scientific=20
Information Inc.
============================================================
(11) THE LEONID METEOR STORMS OF 1833 and 1966
D.J. Asher: The Leonid meteor storms of 1833 and 1966. MONTHLY=20
NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1999, Vol.307, No.4,=20
pp.919-924
ARMAGH OBSERV,COLL HILL,ARMAGH BT61 9DG,NORTH IRELAND
The greatest Leonid meteor storms since the late eighteenth century=20
are generally regarded as being those of 1833 and 1966. They were=20
evidently due to dense meteoroid concentrations within the Leonid=20
stream. At those times, the orbit of Comet 55P/Tempel-Tuttle was=20
significantly nearer that of the Earth than at most perihelion=20
returns, but still some tens of Earth radii away. Significantly=20
reducing this miss distance can be critical for producing a storm.=20
Evaluation of differential gravitational perturbations, comparing=20
meteoroids with the comet, shows that, in 1833 and 1966 respectively,=20
the Earth passed through meteoroid trails generated at the 1800 and=20
1899 returns. Copyright 1999, Institute for Scientific Information=20
Inc.
==========================================================
(13) METEOR STORM FORECASTING
I. Ferrin: Meteor storm forecasting: Leonids 1999-2001. ASTRONOMY AND=20
ASTROPHYSICS, 1999, Vol.348, No.1, pp.295-299
*) UNIV LOS ANDES,CTR THEORET ASTROPHYS,MERIDA 5101,VENEZUELA
We present a method for meteor storm forecasting, that we apply to=20
the Leonids in 1999-2001. The method makes use of a plot where the=20
particle density distribution around the comet is mapped (Fig. 1) and=20
isolines of equal meteor intensity are drawn. The most significant=20
result found is the existence of a ''ridge'' or region of high=20
particle density, that corresponds to the great Leonid storms and=20
that we identify with the ''dust trails'' that Sykes et al. (1990)=20
and Sykes & Walker (1992) found behind all periodic comets. We=20
present detailed calculations of the trajectories of meteoroids that=20
will reproduce this ridge. We predict the intensity of upcoming=20
Leonid showers by the position of the Earth in relation to the=20
isolines. For 1999 we predict a zenith hourly rate (ZHR) of 3.5 K+/-1=20
K. For the year 2000 we can only limit the intensity to 5 K < ZH R <=20
20 K. And for 2001 the ZHR will only reach to 400+/- 100. Copyright=20
1999, Institute for Scientific Information Inc.
==========================================
(14) TRAJECTORY & ORBIT OF THE TUNGUSKA METEORITE REVISITED
V.A. Bronshten: Trajectory and orbit of the Tunguska meteorite=20
revisited. METEORITICS & PLANETARY SCIENCE, 1999, Vol.34, No.SS,=20
pp.A137-A143
VARSHAVSKOYE RD 16-130,MOSCOW 113105,RUSSIA
A critical survey is presented of all determinations of the azimuth=20
and inclination of the Tunguska meteorite's trajectory based either=20
on eyewitness testimonies or on the mathematical treatment of the=20
forest-leveling field in the area of the catastrophe. The eyewitness=20
testimonies collected in the neighborhood of the Nizhnyaya Tunguska=20
River indicate the most probable azimuth of the trajectory projection=20
to be 104 degrees from the north to the east, which is close to the=20
most recent azimuth estimate from the forest-leveling field, 99=20
degrees. For the most part of the trajectory, its inclination could=20
not exceed 15 degrees. However, it is seen from aerodynamic=20
calculations that the combined action of the gravity field and=20
a nonzero aerodynamic lift could increase the inclination to 40=20
degrees as the end of the trajectory was approached. Meteoroid orbits=20
are calculated for a broad family of trajectories with azimuths=20
ranging from 99 degrees (Fast et al., 1976) to 137 degrees (Krinov,=20
1949) and geocentric velocities ranging from 25 to 40 km/s. Orbits=20
with large azimuth values (120 degrees and larger) are shown to=20
belong to the asteroidal type. They are succeeded by the orbits of=20
short-period and long-period comets, whereas very small azimuth=20
values and large geocentric velocities correspond to the region of=20
hyperbolic orbits. Certain restrictions on the possible trajectory=20
azimuths and geocentric velocities of the Tunguska body are imposed=20
by this study. Copyright 1999, Institute for Scientific Information=20
Inc.
==========================================
(15) SIMULATION OF PROCESSES ON COMET NUCLEI
D.W.G. Sears*), H.W. Kochan, W.F. Huebner: Laboratory simulation of=20
the physical processes occurring on and near the surfaces of comet=20
nuclei. METEORITICS & PLANETARY SCIENCE, 1999, Vol.34, No.4,=20
pp.497-525
*) UNIVERSITY OF ARKANSAS,DEPT CHEM & BIOCHEM,COSMOCHEM=20
GRP,FAYETTEVILLE,AR,72701
Laboratory comet simulation experiments are discussed in the context=20
of theoretical models and recent ground-based and spacecraft=20
observations, especially the Giotto observations of P/Halley. The=20
set-up of various comet simulation experiments is reviewed. A number=20
of small-scale experiments have been performed in many laboratories=20
since the early 1960s. However, the largest and most ambitious series=20
of experiments were the comet simulation experiments known as KOSI=20
(German =3D Kometen Simulation). These experiments were prompted by the =
appearance of Comet P/Halley in 1986 and in planning for the European=20
Space Agency's Rossetta mission that was originally scheduled to=20
return samples. They were performed between 1987 and 1993 using the=20
German Space Agency's (DLR) space hardware testing facilities in=20
Cologne. As with attempts to reproduce any natural phenomenon in the=20
laboratory, there are deficiencies in such experiments while there=20
are major new insights to be gained. Simulation experiments have=20
enabled the development of methods for making comet analogues and for=20
exploring the properties of such materials in detail. These=20
experiments have provided new insights into the morphology and=20
physical behavior of aggregates formed from silicate grains likely to=20
exist in comets. Formation of a dust mantle on the surfaces and a=20
system of ice layers below the mantle caused by chemical=20
differentiation have been identified after the insolation of=20
the artificial comet. The mechanisms for heat transfer between=20
the comet's surface and its interior, the associated gas diffusion=20
from the interior of the surface, and compositional, structural, and=20
isotopic changes that occur near the surface have been described by=20
modeling the experimental results. The mechanisms of the ejection of=20
dust and ice grains from the surface and the importance of gas-drag=20
in propelling grains have also been explored. Copyright 1999,=20
Institute for Scientific Information Inc.
==========================================
(16) WEAK RESONANCES DRIVE ASTEROIDS TOWARD TERRESTRIAL=20
PLANETS ORBITS
A. Morbidelli, D. Nesvorny: Numerous weak resonances drive asteroids=20
toward terrestrial planets orbits. ICARUS, 1999, Vol.139, No.2,=20
pp.295-308
*) OBSERV COTE AZUR,BP 4229,F-06304 NICE 4,FRANCE
A systematic exploration of the chaotic structure of the asteroid=20
belt is presented, first taking into account only the perturbations=20
provided by the four giant planets and then including also the=20
effects of the inner planets. We find that both the inner belt (a <=20
2.5 AU) and the outer part of the main belt (a > 2.8 AU) are mostly=20
chaotic. In the outer part of the belt, chaos is due to the presence=20
of numerous mean-motion resonances with Jupiter and three-body=20
resonances, Jupiter-Saturn-asteroid. In the inner belt; chaos is=20
generated by mean motion resonances with Mars and three-body=20
resonances, Mars-Jupiter-asteroid. Due to the chaoticity of the belt,=20
asteroids tend to slowly migrate in eccentricity. This phenomenon of=20
''chaotic diffusion'' allows many bodies in the inner belt to become=20
Mars-crossers. The number of asteroids leaking out from the inner=20
belt is large enough to keep the population of Mars-crossing=20
asteroids in steady state, despite of the short dynamical lifetime of=20
the latter (similar to 25 Myr). We speculate that chaotic diffusion=20
could have substantially eroded the high-eccentricity part of the=20
asteroid belt, thus providing the impactors responsible for the Late=20
Heavy Bombardment phase of the early Solar System. (C) 1999 Academic=20
Press.
==========================================
(18) INTERPLANETARY DUST AS FLUFFY AGGREGATES
R. Nakamura*), H. Okamoto: Optical properties of fluffy aggregates as=20
analogue of interplanetary dust particles. ADVANCES IN SPACE=20
RESEARCH, 1999, Vol.23, No.7, pp.1209-1212
*) KOBE UNIVERSITY,INFORMAT PROC CTR,ROKKO DAI 1-1,KOBE,HYOGO=20
657,JAPAN
Based on the appearance of chondritic porous aggregates collected=20
from stratosphere, we have modeled interplanetary dust particles as=20
fluffy aggregates consisting of submicron-sized spherical monomers.=20
The optical properties are calculated by a modified version of the=20
discrete dipole approximation where the dipole polarizability is=20
determined by the first term of scattering coefficient in the Mie=20
theory. The accuracy of our calculations is confirmed through the=20
comparison with the rigorous solutions for cluster of spherical=20
monomers. It is found that fluffy aggregates have larger cross=20
sections and less resonant structures in the scattering profiles in=20
comparison with the volume-equivalent sphere. Our model results
in consisted behaviors with the observation of zodiacal light,=20
i.e., slow rise towards the backward direction and negative=20
polarization between the scattering angles 160 degrees less than or=20
equal to theta less than or equal to 180 degrees, For two sets of=20
optical constants of dielectric materials, these properties are riot=20
sensitive to the size of an aggregate as long as the monomer size is=20
smaller than the incident wavelength. (C) 1999 COSPAR, Published by=20
Elsevier Science Ltd.
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