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
 



CCCMENU CCC for 1997

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