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(meteorobs) Excerpts from "CCNet, 6 December 1999"
A large and juicy edition of CCNet this time...
Lew
------- Forwarded Message
From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: CCNet, 6 December 1999
Date: Mon, 6 Dec 1999 10:01:13 -0500 (EST)
CCNet, 6 December 1999
-----------------------
[...]
(5) NEWS ON THE LUNAR LEONIDS
Joan and David Dunham <dunham@erols.com>=20
(6) LEONIDS ARTICLE - WITH SOME FLAWS
Daniel Fischer <dfischer@astro.uni-bonndot de>=20
(7) NATURE OF THE TUNGUSKA IMPACTOR
Peter Snow <p.snow@xtra.co.nz>=20
[...]
(9) STABLE CHAOS IN THE ASTEROID BELT
M. Sidlichovsky, ASTRONOMICAL INSTITUTE PRAHA
[...]
(11) SLOW & FAST DIFFUSION IN ASTEROID-BELT RESONANCES
S. Ferraz Mello, UNIVERSITY OF SAO PAULO
[...]
(13) ON THE PERTURBING FUNCTION IN ORBITAL ELEMENTS
I. Tupikova et al., LOHRMANN OBSERVATORY
[...]
(18) SURVIVAL OF LIFE ON ASTEROIDS & COMETS
B. C. Clark et al., LOCKHEED MARTIN ASTRONAUT
========================================================================
(5) NEWS ON THE LUNAR LEONIDS
>From Joan and David Dunham <dunham@erols.com>=20
A summary of the six confirmed lunar impacts is given in the table=20
below. This is an ASCII plain text table that must be viewed with a=20
fixed-space font such as Courier for the columns to line up properly. =20
We are naming these with letters in the order of discovery. The UT=20
date is 1999 November 18. In each case, the events were confirmed on=20
my videotapes made at George Varros' backyard in Mount Airy, Maryland,=20
and the timings are from my tapes. The previously-reported estimates of =
the locations of D and E were rather far off in longitude, according to =
measurements of the video images made by Ben Wun and me earlier today.
Accuracy, Approx. Discovered Selenographic
Name UTC sec. Mag1 Mag2 by Long. Lat. Description
h m s
F 3:05:44.2 0.6 5 9? David Palmer 69W 44N 50km e of Harding
D 3:49:40.40 0.03 3 7 David Palmer 69W 2N w. wall of =
Hevelius
E 4:08:04.1 0.6 5 8 David Palmer 77W 15S 120km SW of Rocca
A 4:46:15.2 0.1 3 8 Brian Cudnik 71W 14N 50km ENE of =
Cardanus
B 5:14:12.93 0.05 7 8 Pedro Sada 58W 15N 200km WNW of Marius
C 5:15:20.23 0.05 4 7 Pedro Sada 59W 21N 75km S Schiaparelli =
Mag1 is the approximate magnitude of the flash estimated from my tape =
on=20
the half-frame on which it first appears. Mag2 is the estimated=20
magnitude a half-frame, or 1/60th second, later. In all cases I can't=20
see any evidence of the flash in the half-frame 1/30th second after the =
first one, except for D, where it seems to appear there at about 9th=20
mag. The selenographic locations should be accurate to within about 2=20
deg. or 50 km, but the locations of F and E could be in error more due=20
to foreshortening near the limb and lack of nearby features in the Moon =
images generated with the Occult program used for the location=20
determination. Their locations can be improved by using a grid overlay =
that we plan to generate. All of these are in the western part of=20
Oceanus Procellarum (Ocean of Storms) except D and E, which are in=20
highlands area a short distance west of the western shore of Oceanus=20
Procellarum. The times of B and C have been determined by Don=20
Stockbauer, Victoria, Texas, after creating an accurately time-inserted =
copy using an IOTA-Manly video time inserter. He also determined the=20
time of A, but for technical reasons to less accuracy; it will be=20
possible to refine it later. D, E, and F have been timed from the tape=20
just using a stopwatch.=20
D seems to be the brightest impact. Besides Palmer's and my videotapes, =
it is also in videotapes by Pedro Sada and by Rick Frankenberger in San =
Antonio, Texas. My image for the event also shows three stars, from=20
north to south (right to left in the image) being 7.6-mag. SAO 146577,=20
8.2-mag. SAO 146578, and 8.9-mag. SAO 146574, all of whose occultations =
were recorded a few minutes later. The first two stars are also=20
visible in David Palmer's frame of the D impact.
Sada reports two more events estimated at about 5th magnitude at=20
4:32:50.8 and 4:34:49.7 UTC, but they have not been found in other=20
tapes (the field of view of my 5-inch telescope used for the 6 known=20
events was aimed at a more southern part of the Moon than usual, so=20
they would have been missed if they occurred a little north of the=20
equator). The 2nd event was fairly close to the terminator. Other=20
possible unconfirmed events (some chance of their being videotape=20
defects) were recorded by me at 4:50:15.9 UTC and by David Palmer at=20
2:42:02.
The images for all six events are at http://iota.jhuapldot edu. That site=20
also has a link to the article about the impacts that was published on=20
page 2B of the December 1st Baltimore Sun, and the NASA news Web site=20
that has an animation of impact A. Some of Palmer's images are on the=20
IOTA Web site at http://www.lunar-occultations.com/iota
The mass of the impacting meteoroids, and the resulting craters, has=20
still not been resolved. Mass estimates range from 50 grams to 20 kg,=20
and crater sizes from several meters to almost 100 meters, in any case=20
probably too small to be visible from earth-based observations.
David Dunham, IOTA, 1999 December 3
Joan and David Dunham
7006 Megan Lane
Greenbelt, MD 20770
(301) 474-4722
dunham@erols.com
========================================================================
(6) LEONIDS ARTICLE - WITH SOME FLAWS
>From Daniel Fischer <dfischer@astro.uni-bonndot de>=20
http://www.sciencenews.org/sn_arc99/12_4_99/fob3.htm - the doubts by
Weissman (last paragraph) seem unfounded as most of the flashes=20
reported by Dunham were imaged by video cameras in *different*=20
locations; thus satellite glints can be firmly excluded, right?=20
Regards, Daniel
>From SCIENCE NEWS ONLINE, 4 December 1999, =20
Vol. 156, No. 23
THE BEST LEONID SHOWER IS YET TO COME?
By R. Cowen
The streaks of light came fast and furious. Some raced across the sky=20
in nearly parallel tracks, leaving behind hazy trails. A few seemed to=20
dive into the moon.
If last month's Leonid meteor shower proved disappointing in the United
States, it took Europe and the Middle East by storm. And if the
predictions of two astronomers continue to hold true, Earth will be in
for a really big show in 2001 and another in 2002.
At the shower's peak, on Nov. 17, some observers saw between 3,000 and
5,000 shooting stars, or meteors, in a single hour. Activity reached a
crescendo at 9:05 p.m. EST - just 3 minutes earlier than predicted by
David J. Asher of Armagh Observatory in Northern Ireland and Rob
McNaught of the Australian National University in Weston.
Scenes from the 1999 Leonid shower: Meteor's fireball and its fading
light seen for more than 20 minutes over the Italian Alps. (Lorenzo
Comolli)
This is the first accurate prediction of a meteor storm, says Brian G.
Marsden of the Smithsonian Astrophysical Observatory in Cambridge,
Mass.
The Leonid meteor shower happens every November, when Earth passes=20
through a stream of dusty debris, or meteoroids, expelled by Comet=20
55P/Tempel-Tuttle. Dust grains slam into Earth's atmosphere and burn,=20
creating the streaks of light known as meteors. About every 33 years,=20
when the comet passes near, Earth encounters a large amount of debris,=20
resulting in a heavy shower or storm.
Exactly which years the Leonid dust particles will generate a storm has =
been difficult to predict. That's because astronomers hadn't realized=20
that the debris stream is composed of distinct, narrow strands of
dust, each expelled by the comet during a different passage by the sun, =
notes Asher. It's a matter of hit or miss: If Earth plows through the=20
center of a dense strand, a storm will occur.
By simulating the motion of strands in the solar system, Asher and=20
McNaught conclude that the dust strand Earth traveled through last=20
month was shed by the comet in 1899. Although that's the same
material the planet traveled through during the spectacular storm of=20
1966, last month's event wasn't as dazzling because Earth crossed the=20
strand's edge rather than its center, Asher says.
Donald K. Yeomans of NASA's Jet Propulsion Laboratory (JPL) in=20
Pasadena, Calif., says he agrees with the pair's explanation for the=20
1999 event. "I do take their future predictions more seriously now," he
adds.
Next year, McNaught and Asher calculate, Earth will pass for the first=20
time through the edge of a band of dust cast off by the comet in 1866,=20
yielding a puny shower. In 2001, however, Earth will plow sequentially=20
through no less than three trails=97debris expelled in 1767, 1699, and=20
1866=97and the light show should prove more stunning than last month's.
In 2002, when Earth again encounters material from 1866, as well as=20
from 1933, the Leonids should also put on a great show, McNaught and=20
Asher say.
Their findings may shed light on a puzzling feature seen just hours=20
after the Leonid shower reached its 1999 peak. Observers saw flashes of =
light near the moon, as if meteoroids had crashed on its surface.=20
Researchers reported the phenomenon in a Nov. 26 circular of the=20
International Astronomical Union.
The brilliance of these flashes requires that the meteoroids have as
much mass as a bowling ball=97a rare but not extraordinary occurrence,
estimates Alan W. Harris of JPL. Moreover, Asher and McNaught calculate
that the moon intercepted a denser part of the 1899 stream than Earth=20
did and thus encountered a greater number of large meteoroids at the=20
time the flashes occurred. However, cautions Paul R. Weissman of JPL,=20
the flashes could merely have been sunlight glinting off satellites or=20
space debris.
References and sources for this article at=20
http://www.sciencenews.org/sn_arc99/12_4_99/fob3ref.htm
>From Science News, Vol. 156, No. 23, December 4, 1999, p. 356.=20
Copyright =A9 1999, Science Service.
========================================================================
(7) NATURE OF THE TUNGUSKA IMPACTOR
>From Peter Snow <p.snow@xtra.co.nz>=20
With regard to V.A. Bronshten's comments re the Nature of the Tunguska=20
impactor , i.e cometary versus asteroidal in nature, he states that no=20
rocks have been found in the area that would suggest asteroidal origin. =
I visited the area 1996 specifically to view rocks that were quite=20
close to the campsite. These rocks were brecciated and were shallowly=20
embedded in deep peat. The Tungu`s who hunted the area prior to the=20
Tunguska explosion, it is said, claimed the stones appeared after the=20
explosion. Smaller fragments of the stones I believe were taken from=20
the site one was described as being glassy in nature. There is a=20
Russian physicist who has studied these rocks, his name escapes me at=20
the moment. I believe his working hypothesis is that they were=20
extraterrestrial in nature. Thought this may be of interest
Dr Peter Snow
========================================================================
(9) STABLE CHAOS IN THE ASTEROID BELT
M. Sidlichovsky: On stable chaos in the asteroid belt. CELESTIAL=20
MECHANICS & DYNAMICAL ASTRONOMY, 1999, Vol.73, No.1-4, pp.77-86
ASTRONOMICAL INSTITUTE PRAHA,BOCNI II 1401,PRAGUE 14131 4,CZECH=20
REPUBLIC
The twenty most chaotic objects found among first hundred of numbered=20
asteroids are studied. Lyapunov time calculated with and without inner=20
planets indicates that for eleven of those asteroids the strongest=20
chaotic effect results from the resonances with Mars. The filtered=20
semimajor axis displays an abrupt variation only when a close approach=20
to Mars takes place. The study of the behaviour of the critical=20
argument for candidate resonances can reveal which is responsible for=20
the semimajor axis variation. We have determined these resonances for=20
the asteroids in question. For the asteroids chaotic even without the=20
inner planets we have determined the most important resonances with=20
Jupiter, or three-body resonances. Copyright 1999, Institute for=20
Scientific Information Inc.
========================================================================
(11) SLOW & FAST DIFFUSION IN ASTEROID-BELT RESONANCES
S. Ferraz Mello: Slow and fast diffusion in asteroid-belt resonances: A =
review. CELESTIAL MECHANICS & DYNAMICAL ASTRONOMY, 1999, Vol.73, No.1-
4, pp.25-37
UNIVERSITY OF SAO PAULO,INST ASTRON & GEOFIS,CAIXA POSTAL 3386,SAO=20
PAULO,BRAZIL
This paper reviews recent advances in several topics of resonant=20
asteroidal dynamics as the role of resonances in the transportation of=20
asteroids and asteroidal debris to the inner and outer solar system;=20
the explanation of the contrast of a depleted 2/1 resonance (Hecuba=20
gap) and a high-populated 3/2 resonance (Hilda group); the overall=20
stochasticity created in the asteroid belt by the short-period=20
perturbations of Jupiter's orbit, with emphasis in the formation of=20
significant three-period resonances, the chaotic behaviour of the outer =
asteroid belt, and the depletion of the Hecuba gap. Copyright 1999,=20
Institute for Scientific Information Inc.
========================================================================
(13) ON THE PERTURBING FUNCTION IN ORBITAL ELEMENTS
I. Tupikova*), M. Soffel, S. Klioner: On the classical expansion of the
perturbing function in individual orbital elements. CELESTIAL MECHANICS&
DYNAMICAL ASTRONOMY, 1999, Vol.74, No.3, pp.147-152
*) LOHRMANN OBSERV,INST PLANETARE GEODAESIE,MOMMSENSTR 13,D-01062
DRESDEN,GERMANY
Starting from the classical expansion of the perturbing function in the =
three-body problem, the transformation to individual orbital elements=20
is performed in principle up to any degree in small parameters. Some=20
corrections to the results presented in the well-known article by Yuasa
on secular perturbations of asteroids are given. Consequences for the=20
expansion of the indirect part of the perturbing function are=20
discussed. Copyright 1999, Institute for Scientific Information Inc.
========================================================================
(18) SURVIVAL OF LIFE ON ASTEROIDS & COMETS
B. C. Clark*), A.L. Baker, A.F. Cheng, S.J. Clemett, D. McKay,=20
H.Y. McSween, C.M. Pieters, P. Thomas, M. Zolensky: Survival of life on =
asteroids, comets and other small bodies. ORIGINS OF LIFE AND EVOLUTION =
OF THE BIOSPHERE, 1999, Vol.29, No.5, pp.521-545
*) LOCKHEED MARTIN ASTRONAUT,ADV PLANETARY STUDIES GRP,DENVER,CO
The ability of living organisms to survive on the smaller bodies in our
solar system is examined. The three most significant sterilizing=20
effects include ionizing radiation, prolonged extreme vacuum, and=20
relentless thermal inactivation. Each could be effectively lethal, and=20
even more so in combination, if organisms at some time resided in the=20
surfaces of airless small bodies located near or in the inner solar=20
system. Deep within volatile-rich bodies, certain environments=20
theoretically might provide protection of dormant organisms against=20
these sterilizing factors. Sterility of surface materials to tens or=20
hundreds of centimeters of depth appears inevitable, and to greater=20
depths for bodies which have resided for long periods sunward of about=20
2 A.U. Copyright 1999, Institute for Scientific Information Inc.
----------------------------------------
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