PLEASE NOTE:
*
Date sent: Wed, 26 Nov
1997 09:56:32 -0500 (EST)
From:
Benny J Peiser <B.J.PEISER@livjm.ac.uk
To:
cambridge-conference@livjm.ac.uk
Priority: NORMAL
CAMBRIDGE-CONFERENCE DIGEST, 26 November 1997
(1) COMET OR ASTEROID?
(2) 1997 LEONIDS STORM
(3) OXFORD VI INTERNATIONAL CONFERENCE ON ARCHAEOASTRONOMY AND
ASTRONOMY IN CULTURE
=========================================================================
(1) COMET OR ASTEROID?
ESO Education and Public Relations Dept.
ESO Press Release 11/97
For immediate release: 24 November 1997
COMET OR ASTEROID?
When is a minor object in the solar system a comet? And when
is it an
asteroid?
Until recently, there was little doubt. Any object that was
found to display
a tail or appeared diffuse was a comet of ice and dust grains,
and any that
didn't, was an asteroid of solid rock. Moreover, comets normally
move in
rather elongated orbits, while most asteroids follow
near-circular orbits
close to the main plane of the solar system in which the major
planets move.
However, astronomers have recently discovered some
`intermediate'
objects which seem to possess properties that are typical for
both
categories. For instance, a strange object (P/1996 N2 --
Elst-Pizarro) was
found last year at ESO (ESO Press Photo 36/96) which showed a
cometary tail,
while moving in a typical asteroidal orbit. At about the same
time, American
scientists found another (1996 PW) that moved in a very elongated
comet-type
orbit but was completely devoid of a tail.
Now, a group of European scientists, by means of observations
carried out at
the ESO La Silla observatory, have found yet another object that
at first
appeared to be one more comet/asteroid example. However,
continued and more
detailed observations aimed at revealing its true nature have
shown that it
is most probably a comet. Consequently, it has received the
provisional
cometary designation P/1997 T3.
The Uppsala-DLR Trojan Survey
Some time ago, Claes-Ingvar Lagerkvist (Astronomical
Observatory,
Uppsala, Sweden), in collaboration with Gerhard Hahn, Stefano
Mottola,
Magnus Lundstroem and Uri Carsenty (DLR, Institute of Planetary
Exploration, Berlin, Germany), started to study the distribution
of
asteroids near Jupiter. They were particularly interested in
those that move
in orbits similar to that of Jupiter and which are located
`ahead' of
Jupiter in the so- called `Jovian L4 Lagrangian point'. Together
with those
`behind' Jupiter, these asteroids have been given the names of
Greek and
Trojan Heroes who participated in the famous Trojan war. Thus
such asteroids
are known as the Trojans and the mentioned programme is referred
to as the
Uppsala- DLR Trojan Survey.
In September and October/November 1996, the ESO Schmidt
telescope
was used to cover about 900 square degrees twice centered on the
sky
field in the direction of the Jovian L4 point. The observations
were made by
ESO night-assistants Guido and Oscar Pizarro. By inspection of
those from
September, Claes-Ingvar Lagerkvist found a total of about 400
Trojan
asteroids, most of which were hitherto unknown. Their accurate
positions
were measured on a two-coordinate measuring machine at the ESO
Headquarters
in Garching (Germany). During the same period, the 0.6-m Bochum
telescope at
La Silla was used for additional observations of positions and
magnitudes.
An asteroid with a tail?
A new object was found by Claes-Ingvar Lagerkvist on a film
obtained with
the ESO 1-metre Schmidt telescope on October 1, 1997. The
appearance was
that of a point light source, i.e. it was presumably of
asteroidal nature,
cf. ESO Press Photo 31a/97.
However, when Andreas Nathues (DLR, Institute of Planetary
Exploration) soon
thereafter obtained seven unfiltered CCD images on three
consecutive nights
with the 60-cm `Bochum telescope' at La Silla, Uri Carsenty found
a tail
extending 15 arcseconds in the WSE direction from the point
source, cf. ESO
Press Photo 31b/97. The (red) magnitude was about 19, or 150,000
times
fainter than what is visible to the naked eye. More observations
were
obtained at La Silla during the following nights, confirming the
persistent
presence of this tail.
NTT observations confirm the cometary nature of P/1997 T3
In late October 1997, further images of the new object and its
tail were
taken with the ESO 3.5-m New Technology Telescope (NTT) at La
Silla, cf. ESO
Press Photo 31c/97. On these, the narrow tail was seen to be at
least 90
arcsec long and pointing roughly in the Sun direction. The steady
appearance
and the sunward orientation of the tail indicates that it
consists of dust.
Moreover, a preliminary image analysis shows the presence of a
weak and very
condensed coma of dust grains around the nucleus.
Interestingly, a series of images through several broadband
filters with a
total of almost 30 min exposure time did not show any trace of a
normal,
anti-sunward tail seen in most comets.
Still, these observations indicate that the object resembles a
typical comet
much more than originally thought. This is also supported by the
fact that
its orbit, calculated on the basis of positional observations
during the
past month, has been found to be moderately elongated
(eccentricity 0.36).
The mean distance to the Sun is 6.67 AU (1000 million
kilometres), but it
comes as close as 4.25 AU (635 million kilometres) at its
perihelion. The
orbital period is about 17 years.
More observations needed!
It will be interesting to follow this new object in coming
years. Will it
remain `cometary' or will the unusual tail disappear after a
while? Could it
be that some `asteroids' in `cometary' orbits, if observed in
more detail
with a larger telescope, as was done in this case with the NTT,
will also
turn out to have a faint coma and even a tail?
It is at this moment still unknown which implications the
discovery of
apparently `intermediate' objects may have on our understanding
of the
origin and evolution of the solar system. In particular, it is
not at all
clear whether they represent a completely new class of objects
with an
internal structure (and composition?) that is significantly
different from a
`dirty-snowball' cometary nucleus or a rocky asteroid. It may
also be that
some asteroids have substantial deposits of icy material on or
near the
surface that may be set free under certain circumstances and
mimic cometary
activity. This might in theory happen by collisions with other,
smaller
objects or due to an internal heat source. Only further
observations of such
objects will allow to tell.
Where to find more information
Here are some WWW-addresses where more useful information may
be
obtained about the comet/asteroid phenomenon (the clickable links
are
available at the web-based version of this Press Release at the
ESO
website)::
----------------------------------------------------------------------------
Text and photos with all links are available on the ESO Website
at URL:
http://www.eso.org/outreach/press-rel/pr-1997/
----------------------------------------------------------------------------
======================================================================
(2) 1997 LEONIDS STORM
From: kaze@tcp-ip.or.jp
Subject: 1997 Leonids storm in Hawaii
Date: Sat, 22 Nov 1997 22:44:39 +0900
Dear Dr. Marsden:
I would like to submit you as an observational report for IAUC
that the TV
Leonid meteors' short-time outburst was detected at Mt. Mauna Kea
in Hawaii
by Masao Kinoshita in the morning on November 17 LT(LT=UT-10h)
1997.
Masao Kinoshita(Osaka, Japan) observed 1997 Leonids'
short-time storm
using TV systems at Nov. 17.5637 UT corresponding the solar
longitude of
235.27 deg.(2000.0 Eq.) at Mauna Kea(height 3,500 m), Hawaii. The
storm had
continued for only 2 sec. from 13h31m51s to 53s UT and more than
100-150
meteors appeared in the video pictures(70deg.*50deg. of the
celestial
sphere) for that 2 sec. Used TV systems consisted of an
image
intensifier(Hamamatsu), a video camera(SONY) and a lens with
focal lengths
of 24 mm/F 1.4(Canon).
This Leonids storm consisted of -2 to 4 mag meteors and all
meteors
appeared within 10 deg. width view. Simply corrected, hourly rate
of
this storm amounts to 180,000 to 200,000. Excluding the
term of this
storm, hourly rate of TV Leonids was 30-40 during 13h -16h UT.
Mail Sender: Kazuhiro Suzuki, Toyokawa, Aichi, Japan
FAX:+81-5337-6-2852 E-mail: kaze@tcp-ip.or.jp
URL: http://www.tcp-ip.or.jp/~kaze/rmd.htm
======================================================================
(3) OXFORD VI INTERNATIONAL CONFERENCE ON ARCHAEOASTRONOMY AND
ASTRONOMY IN CULTURE
From: Museo de La Ciencia y El Cosmos de Tenerife
<museo@cosmos.mcc.rcanaria.es
FIRST ANNOUNCEMENT
La Laguna, November 1997
It is a pleasure to inform you that, hopefully, in two years
from
now we will be cellebrating the Oxford VI International
Conference
on Archaeoastronomy and Astronomy in Culture and the S.E.A.C.
1999
Annual Meeting in the city of San Cristobal de La Laguna,
(Tenerife,
Canary Islands, Spain), forward on the topic Astronomy and
Cultural
Diversity.
The Conference will be jointly organized by:
* Instituto de Astrofísica de Canarias
* Museo de la Ciencia y el Cosmos del Cabildo de Tenerife
* Universidad de La Laguna (Departamentos de Astrofísica y de
Prehistoria, Antropología e Historia Antigua)
* with the collaboration of the Archaeological Museum of
Tenerife.
The meeting would last from Morning of Monday, June 21st,
1999, to
late afternoon on Tuesday, June 29th, 1999, La Laguna, Tenerife.
* General Topics and Methodology
* New Research in Traditional Areas: Eurasia
* New Research in Traditional Areas: Precolumbian America
* From the Atlas to the Caucasus: the other side of the
Mediterranean
before & after Islam
* Astronomy in Islands: a peculiar evolution?
* The Voyage of the Sages: Mutual Influences and Interchanges for
Astronomy in Culture
* Ethnomathematics and Ethnoastronomy: the sky of living people
* The Origin of the Constellations
* Research in New Areas: Exotic Astronomies and Cultural
Diversity
We recommend you to visit our web site
http://www.mcc.rcanaria.es/oxford6/oxford6.htm
Dr. Juan Antonio Belmonte
Chairman Oxford VI Conference
Instituto de Astrofísica de Canarias
C/ Vía Lactea S.N.
38200 La Laguna, Tenerife, Spain
Tph: 34-22-605265 or 34-22-263454
Fax: 34-22-605210 or 34-22-263295
e-mail: jba@iac.es