PLEASE NOTE:
*
CCNet DIGEST 10 July 1998
-------------------------
"The End of the World Cup is
nigh"!
(1) HISTORICAL IMPACT EVENTS
Ted Bryant <ted_bryant@uow.edu.au>
(2) NEO DISCOVERY RATES
Lew Gramer <dedalus@latrade.com>
(3) ASTRONOMERS DISCOVER A NEARBY STAR SYSTEM JUST LIKE OUR OWN
SOLAR
SYSTEM
Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
(4) SOME MUSINGS ON ATMOSPHERIC PRESSURE WAVES
E.P. Grondine <epgrondine@hotmail.com>
(5) UNUSUAL SPECTRA OF NEAR-EARTH ASTEROIDS & EXTINCT COMETS
M.D. Hicks et al., CALTECH
(6) ASTEROID 1991 VH
P. Pravec et al.,ACADEMY OF SCIENCE OF THE
CZECH REPUBLIC
(7) HDO IN COMET 1996 B2 (HYAKUTAKE)
D. Bockelee Morvan et al., PARIS OBSERVATORY
==================
(1) HISTORICAL IMPACT EVENTS
From Ted Bryant <ted_bryant@uow.edu.au>
Dear Dr. Peiser:
I am involved in the description of geological signatures of
catastrophic tsunami. Most of this work is concentrated around
the
southeast coast of New South Wales, Australia. Recently we
extended our
work to Queensland and Western Australia. This has led us to
believe
that these three coastlines were severely impacted by
catastrophic
tsunami about 400 radiocarbon years ago. As the coastlines do not
share
a common body of water, we now believe that we are looking at the
impact of a fragmenting comet into the oceans around Australia,
and the
generation of catastrophic tsunami. The New South Wales coast
evidence
shows that there have probably been 6 events along
this coast in the
last 6-7,000 years. We think one of the biggest events occurred
very
early and have some evidence to suggest that it was also
generated by a
comet impact that was shared by other sites globally. Aborigines
certainly witnessed these events. They have legends both for
comet
impacts and tsunami. For more information I invite you to visit
my web
sites at
http://www.uow.edu.au/science/geosciences/staff/EAB.htm
http://www.uow.edu.au/science/geosciences/research/tsun.htm
Sincerely,
Dr. Ted Bryant
Assoc. Prof. in Geosciences,
University of Wollongong,
Wollongong, N.S.W.,
Australia, 2522.
phone: 61-242-213-172
fax: 61-242-214-250
e-mail: ted_bryant@uow.edu.au
===========================
(2) NEO DISCOVERY RATES
From Lew Gramer <dedalus@latrade.com>
[as posted on meteororb-list]
Saw this on the AAVSO list, and thought it (somewhat) more
appropriate
here.
Lew
------- Forwarded Message
To: "AAVSO-DISCUSSION" <aavso-discussion@physics.mcmaster.ca>
From: "Marvin Baldwin" <mbald00@hsonline.net>
Subject: Re: June observing
Date: Sun, 05 Jul 98 00:24:14 PDT
Brian Skiff just laid out some amazing statistics about asteroid
discoveries and I've gotta see if I'm understanding this
correctly. The
asteroid survey telescope, the LONEOS Schmidt, just in the month
of May
alone, took data resulting in 8000 asteroid position measurements
and
the discovery of 145 previously unknown asteroids??
At the same time, month of May alone, the military project,
LINEAR,
took data resulting in 80,000 asteroid position measurements and
discovered 3600 previously unknown asteroids about 1% of which
were
determined to be near-Earth objects??
Are these 3600+ newly found asteroids tracked sufficiently to fix
their
orbits or are most of them simply lost until they are picked up
again
in the future in a similar manner with the possibility of
matching them
up with the old data and fixing their orbits at that time?
Are most of these new asteroids being found when they are nearby
or are
they being spotted half way across the solar system?
Then there is the question concerning the size of the near-Earth
objects (statistically speaking) and the additional question,
concerning the discovery rate, as to how many are expected to be
found
eventually.
Marv Baldwin
Butlerville, Indiana, USA
----------
From Brian Skiff
Arne asked some possibly rhetorical questions about our June
observing,
and we've chatted since then, but I'll fill in folks here in case
there's some interest.
We try to run the LONEOS Schmidt, which is an asteroid survey
telescope, whenever the Moon is less than 80-percent illuminated.
After
the June Full Moon, my colleague Bruce Koehn observed for a few
nights
with our summer student Chris Onken (from Univ of Minnesota),
then I
took over for a couple of nights. Actually, these were
formal training
nights for Chris, and I didn't do much besides watch. On
the first of
these nights Chris chose some fields that included our first
near-Earth
asteroid discovery, 98MQ, so things started well. Chris worked
alone at
LONEOS for three more nights while I did follow-up astrometry of
asteroids at our 1.1-m telescope; on the last of these nights I
got a
preliminary lightcurve for 98MQ (period of 6-7 hours, but an
amplitude
of only ~0.06 mag.---tough to do accurately at mag. 17.5 with the
1.1-m
telescope). Then I was back at LONEOS for the succeeding
nine nights,
violating all kinds of Arizona labor laws in the process.
Just about
gave it all away mentally/physically, too. Should have gone
directly
back to Sun-like stars photometry at the venerable 21-inch on
Mars
Hill, but took two days off to recoup. (If I sounded completely
incoherent on the NPR interview that ran last Monday, it was
because
I'd just gotten out of bed after the thirteenth of the fourteen
nights
when they called.)
We're taking about 200 data frames of 17.4Mb each on these short
summer
nights; call it 3.5Gb (8Mb per minute!). The reduction
software, which
Bruce and Chris are working on, is primitive enough that we
barely get
a handle on the moving objects, and certainly nothing's been done
to
pick up the variables and supernovae that doubtless show up on
these
frames. We're covering about 600 square degrees three times
each night
to R mag. 18, so there's a lot of real estate involved. The
reductions,
which are done on the fly by four high-end Pentium II towers (no
keyboard or monitor), are basically complete for the moving
objects
only a few minutes after the final frame is taken. In May, a much
cloudier and problem-plagued run, we reported about 8000 asteroid
positions to the Minor Planet Center, among which were 145
discoveries.
To put this in perspective, during the same period LINEAR (a
military
project) produced _80,000_ positions and was credited with over
3600
asteroid discoveries, including half a dozen comets and basically
all
the near-Earth objects found in the interval (some three dozen).
(Your
military tax dollars at work!)
I found the June dark run very satisfying aesthetically. Thanks
to the
low winter-like extinction values, which Arne reported on (around
0.12-0.14 in V), the nights were absolutely gorgeous. The evening
&
morning twilights were likewise wonderfully saturated in
color. I
found the zodiacal light was readily visible both morning &
evening; I
got to see a fairly old and a quite young Moon; saw the Pleiades
go
from being difficult in bright twilight to being well up in full
darkness as Venus slipped past it; saw Aldebaran within a day or
two of
heliacal rising; saw the activity associated with the unexpected
Pons-Winnecke meteor shower; spent parts of several nights doing
visual
deep-sky observing in the Milky Way and eastwards with my Pronto
telescope, which showed stars to V mag. 14 on these glorious
nights.
The most amazing thing of all, of course, was that I got _paid_
to do
this! (Your NASA tax dollars at work!)
It appears to be clearing up again tonight, so I'm off to spend
some
NSF tax dollars doing photometry on stars....
All for now.
Brian
==========================
(3) ASTRONOMERS DISCOVER A NEARBY STAR SYSTEM JUST LIKE OUR OWN
SOLAR
SYSTEM
From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
Joint Astronomy Center
Contact numbers:
Jane Greaves (JAC)
jsg@jach.hawaii.edu
phone (USA) (808) 969 6562 (until July 3rd)
phone (USA) (805) 683 6722, room 214 (from July 5th)
USA Press Contact:
Stuart Wolpert (UCLA)
stuartw@college.ucla.edu
phone (USA) (310) 206 0511
UK Press Contact:
Helen Walker (RAL)
hjw@ast.star.rl.ac.uk
phone (UK) 01235 446490
Wednesday 8th July, 1998
Astronomers discover a nearby star system just like our own Solar
System
HILO, HAWAII -- An international team of astronomers from the
Joint
Astronomy Centre (JAC) in Hawaii, the University of California at
Los
Angeles (UCLA) and the Royal Observatory in Edinburgh announced
today
the discovery of a ring of dust particles around a nearby star,
Epsilon
Eridani, that appears to signify a Solar System very similar to
our
own.
The ring is "strikingly similar" to the outer comet
zone in our Solar
System, and shows an intriguing bright region that may be
particles
trapped around a young planet, said JAC astronomer Jane Greaves,
who
led the research team.
"What we see looks just like the comet belt on the outskirts
of
our Solar System, only younger," said Greaves, who presented
the
findings today at the "Protostars and Planets"
Conference in Santa
Barbara. "It's the first time we've seen anything like this
around
a star similar to our Sun. In addition, we were amazed to see a
bright
spot in the ring, which may be dust trapped in orbit around a
planet."
Why is Epsilon Eridani so interesting?
Greaves was a member of the international team that reported new
images
of dusty disks around the hotter stars Fomalhaut and Vega in
April
(Dusty Disks). However, the new image of Epsilon Eridani is even
more
exciting for several reasons:
"Epsilon Eridani is far more similar to our Sun than either
Vega
Fomalhaut." she said. "This star system is a strong
candidate for
planets, but if there are planets, it's unlikely there could be
life
yet. When the Earth was this young, it was still being very
heavily
bombarded by comets and other debris."
"It is also a star in our local neighbourhood, being only
about 10
light years away, which is why we can see so much detail in the
new
image"
Epsilon Eridani is clearly visible to the naked eye, in the
constellation Eridanus (the River), which stretches from the foot
of
Orion (near the bright star Rigel) to the 9th brightest star in
the
sky, the southerly Achernar (barely visible from the USA and
Europe).
Epsilon Eridani is among the 10 closest star systems to the
Earth.
"If an astronomer could have seen what our Solar System
looked like
four billion years ago, it would have been very much as Epsilon
Eridani
looks today," said Benjamin Zuckerman, UCLA professor of
physics and
astronomy. "This is a star system very like our own, and the
first time
anyone has found something that truly resembles our Solar System;
it's
one thing to suspect that it exists, but another to actually see
it,
and this is the first observational evidence."
The research team -- which also includes astronomers from the
University of Arizona, University College London, and the
Rutherford
Appleton Laboratory -- has submitted its findings to the
Astrophysical
Journal Letters, the most widely-read scholarly journal in
astronomy.
More about the discovery:
Beyond Pluto in our Solar System is a region containing more than
70,000 large comets, and hundreds of millions of smaller ones,
called
the "Kuiper belt". The image obtained by Greaves' team
shows dust
particles that the astronomers believe are analogous to our
Kuiper belt
at the same distance from Epsilon Eridani as the Kuiper belt is
from
our Sun. Although the image cannot reveal comets directly, the
dust
that is revealed is believed to be debris from comets, Greaves
said.
Epsilon Eridani's inner region contains about 1,000 times more
dust
than our Solar System's inner region, which may mean it has about
1,000
times more comets, the astronomers said. Epsilon Eridani is
believed to
be only 500 million years to 1 billion years old; our Sun is
estimated
to be 4.5 billion years old, and its inner region is believed to
have
looked very similar at that age.
In our Solar System, the first 600 million years was a time of
"heavy
bombardment" when the planets were assaulted by massive
meteorites and
other celestial objects until the gravitation of Jupiter and
Saturn
cleaned out these destructive objects. Life on Earth probably did
not
start until after the era of heavy bombardment, said JAC
astronomer
Wayne Holland.
How was the new image obtained?
The new image -- which is from short-radio wavelengths, and is
not an
optical picture -- was obtained using the 15-meter James Clerk
Maxwell
Telescope at the Mauna Kea Observatory in Hilo, Hawaii. The JCMT
is the
world's largest telescope dedicated to the study of light at
"submillimeter" wavelengths. The team of astronomers
used a
revolutionary new camera called SCUBA (Submillimeter Common User
Bolometer Array), which was built by the Royal Observatory in
Edinburgh
(which is now the UK Astronomical Technology Centre). SCUBA uses
detectors cooled to a tenth of a degree above absolute zero (-273
degrees Celsius) to measure the tiny amounts of heat emission
from
small dust particles at a wavelength close to one-millimeter.
Implications and mysteries of the new discovery
What is the significance of the similarity between Epsilon
Eridani and
our own Solar System?
"The implication is that if there is one system similar to
ours at such
a close star, presumably there are many others," Zuckerman
said. "In
the search for life elsewhere in the universe, we have never
known
where to look before. Now, we are closing in on the right
candidates in
the search for life."
Epsilon Eridani is probably too young to support even primitive
life,
the astronomers said, but there may be other similar star systems
that
are billions of years older, and are good candidates to search
for
life. Although astronomers have not yet located a star system
that is
the right age with the right atmosphere to support life, they are
getting closer.
A region near the star that is partially evacuated indicates that
planets may have formed, the astronomers said; the presence of
planets
is the most likely explanation for the absence of dust in this
region
because planets absorb the dust when they form.
What is the bizarre bright spot in the image obtained by the
astronomers?
"There may be a planet stirring up the dust in the ring and
causing the
bright spot," said Bill Dent of the Royal Observatory,
Edinburgh, "or
it could be the remnants of a massive collision between
comets."
Epsilon Eridani is about three-quarters as massive as the sun,
but only
one-third as luminous. When astronomer Frank Drake conducted the
first
serious search for radio signals from other civilizations in the
late
1950s, Epsilon Eridani was one of the first two stars he studied.
Today, researchers know something Drake did not: Epsilon Eridani
is
much too young to have intelligent life. However, the new image
shows
there may be at least one planet, and perhaps life in the future.
In addition to Greaves, Holland, Zuckerman and Dent, the
astronomers on
the project are Gerald Moriarty-Schieven and Tim Jenness at JAC;
Harold
Butner at the University of Arizona, Tucson; Walter Gear at
University
College London; Helen Walker at the Rutherford Appleton
Laboratory; and
UCLA graduate students Richard Webb and Chris McCarthy.
Information and images are available on the World Wide Web at
website
http://www.jach.hawaii.edu/News/kbelt.html.
The JCMT is operated by the Joint Astronomy Centre, on behalf of
the UK
Particle Physics and Astronomy Research Council, the Netherlands
Organisation for Scientific Research, and the National Research
Council
of Canada. This work was also supported, in part, by NSF and NASA
grants to UCLA.
================
(4) SOME MUSINGS ON ATMOSPHERIC PRESSURE WAVES
From E.P. Grondine <epgrondine@hotmail.com>
Benny -
Several days ago I read a short piece in which it was claimed
that two
previously unknown small tribes of people had been discovered
living in
isolation on the north coast of Indonesia. These people
supposedly
have dark skin and dark hair, which is not that unusual in that
part of
the world, but what was truly unusual was that it was claimed
that the
people of these tribes supposedly communicate not with speech but
entirely by sign language.
This immediately called to my mind Charles Pellegrino's most
recent
book on the myth of Atlantis and the explosion of Thera,
"Unearthing
Atlantis". In this work Pellegrino had speculated that
the reported
deafness of both Moses and Murshilishi might have been caused by
an
incredibly loud sound which accompanied the explosion of Thera.
Pellegrino calculated an estimate of the size of the noise and
how far
the atmospheric shock wave must have traveled, and concluded that
this
hypothesis was entirely likely.
Thinking along these lines, it seems to me that some impact
explosions
must also have produced sounds so loud as to be deafening. I do
not
think that this effect of impact explosions has been widely
noted, and
I do not think that researchers may be on the lookout for reports
of
wide-spread deafness.
A little further down this path, the K/T event must have produced
a
tremendous atmospheric shock wave, one that certainly must have
led to
the loss of hearing by every animal on Earth. An eyeball
estimate of
the K/T shockwave leads me to suspect that not only must it have
been
big enough to lead to deafness, indeed, it was probably large
enough to
rupture the cells in the lungs of every animal on Earth exposed
to it.
I have observed that the animals which survived the K/T impact
event
were those which burrowed and lived at least part of the time
below
ground. I used to think that this burrowing allowed them to
escape the
fire caused by the K/T impactor, a fire which must effectively
have
burned up the entire surface of the Earth. Now, I wonder if
the other
animals may not have died even earlier. In any case,
determining the
exact cause of death will lead to much better models of K/T size
impacts, and so this is probably best left to the specialists.
Returning to our Indonesian tribes, it would be lovely if they
were
survivors of the "wall of water" impact, but it is most
likely that
they are either simply a fraud like the purported primitive
people
which were supposedly "discovered" in the Philippines
some years back,
or that they may have simply developed and inherited the lack of
hearing through isolated breeding.
Ah well, no harm done in speculating (at least of the scientific
variety), and in any case it will be most interesting to see how
these "new" tribes turn out.
Best wishes -
Ed
=======================
(5) UNUSUAL SPECTRA OF NEAR-EARTH ASTEROIDS & EXTINCT COMETS
M.D. Hicks*), U. Fink & W.M. Grundy: The unusual spectra of
15
near-Earth asteroids and extinct comet candidates. ICARUS, 1998,
Vol.133, No.1, pp.69-78
*) CALTECH, JET PROP LAB, MS 183 501, 4800 OAK GROVE DR,
PASADENA, CA,
91109
We present moderate resolution reflectance spectra from 0.55 to
1.0 mu
m for 15 near-Earth asteroids and extinct cometary nuclei
candidates
obtained at the Catalina Station 1.54-m telescope near Tucson,
Arizona.
Though our limited wavelength coverage often makes firm
classification
difficult, an analysis of our measurements reveals that there is
an
over-representation of asteroids with unusually deep 0.9-to 1-mu
m
absorption features, Several of our objects have spectra
consistent
with Q-type asteroids and within the limits of our
signal-to-noise
ratio, are compatible with a chondritic composition. It is
apparent
that the near-Earth asteroids as a population have an unusual
taxonomic
distribution, one that is much closer to that of meteoritic falls
than
may have been previously assumed. (C) 1998 Academic Press.
===============
(6) ASTEROID 1991 VH
P. Pravec*), M. Wolf, L. Sarounova: Occultation/Eclipse events in
binary asteroid 1991 VH. ICARUS, 1998, Vol.133, No.1, pp.79-88
*) ACADEMY OF SCIENCE OF THE CZECH REPUBLIC, ASTRON INST,
CZ-25165
ONDREJOV, CZECH
We present the results of photometric observations of the Apollo
asteroid 1991 VH. Its lightcurve consists of two components: the
first
is the rotational lightcurve with period P-s = (0.109327 +/-
0.000003)
d and amplitude 0.09 mag, while the second, with period P-t =
(1.362
+/- 0.001) d, shows two minima with depth 0.16-0.19 mag, each
with a
duration of about 0.10 d, and little or no variation at phases
between
them. We present a model of the occulting/eclipsing binary
asteroid
with the secondary-to-primary diameter ratio d(s)/d(p) = 0.40
that
explains the observed lightcurve, In this model, the primary's
rotation
is not synchronized with the orbital motion and produces the
short-period lightcurve component (P-s). The orbital period is
P-1. The
mutual orbit's semimajor axis is estimated to be a (2.7 +/- 0.3)
d(p);
the eccentricity is 0.07 +/- 0.02. The similarity between the
lightcurve of 1991 VH and those of 1994 AW(1) (Pravec and Hahn,
Icarus
127, 431, 1997) and (3671) Dionysus (Mottola et al. 1997, IAU
Circular
6680) suggests that binary asteroids may be common among
near-Earth
asteroids. Based on the three known cases, we tentatively derive
some
typical characteristics of this new class of asteroids. They are
mostly
consistent with the hypothesis that binary asteroids are
generated by
tidal disruptions of weak, gravitationally bound aggregates
(so-called
''rubble piles'') during encounters with the Earth (Bottke and
Melosh,
Nature 281, 51, 1996). A possible relationship between the
population
of binary asteroids and the belt of small near-Earth asteroids is
discussed. (C) 1998 Academic Press.
==================
(7) HDO IN COMET 1996 B2 (HYAKUTAKE)
D. Bockelee Morvan*), D. Gautier, D.C. Lis, K. Young, J. Keene,
T.
Phillips, T. Owen, J. Crovisier, P.F. Goldsmith, E.A. Bergin, D.
Despois, A. Wootten: Deuterated water in comet C 1996 B2
(Hyakutake)
and its implications for the origin of comets. ICARUS, 1998,
Vol.133,
No.1, pp.147-162
*) PARIS OBSERVATORY,F-92195 MEUDON, FRANCE
The close approach to the Earth of Comet C/1996 B2 (Hyakutake) in
March
1996 allowed searches for minor volatile species outgassed from
the
nucleus. We report the detection of deuterated water (HDO)
through its
1(01)-0(00) rotational transition at 464.925 GHz using the
Caltech
Submillimeter Observatory. We also present negative results of a
sensitive search for the J(5-4) line of deuterated hydrogen
cyanide
(DCN) at 362.046 GHz. Simultaneous observations of two rotational
lines
of methanol together with HDO in the same spectrum allow us to
determine the average gas temperature within the telescope beam
to be
69 +/- 10 K. We are thus able to constrain the excitation
conditions in
the inner coma and determine reliably the HDO production rate as
(1.20
+/- 0.28) x 10(26) s(-1) on March 23-24, 1996. Available IR, UV,
and
radio measurements led to a water production rate of (2.1 +/-
0.5) x
10(29) s(-1) at the time of our HDO observations. The resulting
D/H
ratio in cometary water is thus (29 +/- 10) x 10(-5), in good
agreement
with the values of(30.8-(+3.8)(5.3)) x 10(-5) (H. Balsiger et
al.,
1995, J, Geophys. Res. 100, 5827-5834). and (31.6 +/- 3.4) x
10(-5) (P.
Eberhard et al., 1995, Astron. Astrophys. 302, 301-316)
determined in
Comet P/Halley from in situ ion mass spectra, The inferred 3
sigma
upper limit for the D/H ratio in HCN is 1%. Deuterium abundance
is a
key parameter for studying the origin and the early evolution of
the
Solar System and of its individual bodies. Our HDO measurement
confirms
that, in cometary water, deuterium is enriched by a factor of at
least
10 relative to the protosolar ratio, namely the D/H ratio in H-2
in the
primitive Solar Nebula which formed from the collapse of the
protosolar
cloud. This indicates that cometary water has preserved a major
part of
the high D/H ratio acquired in this protosolar cloud through
ion-molecule isotopic exchanges or grain-surface reactions and
was not
re-equilibrated with Hz in the Solar Nebula. However, there are
strong
presumptions that interstellar grains were partly mixed in the
early
nebula prior to cometary formation with water reprocessed in the
warm
inner part of the nebula and transported by turbulent
diffusion.
Scenarios of formation of comets consistent with these results
are
discussed. (C) 1998 Academic Press.
----------------------------------------
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