[Index]

(meteorobs) Excerpts from “CCNet 19/2001 – 2 February 2001”

  • Subject: (meteorobs) Excerpts from “CCNet 19/2001 – 2 February 2001”
  • From: Lew Gramer
  • Date: Fri, 02 Feb 2001 12:09:22 -0500
------- Forwarded Message

From: Benny Peiser <B.J.Peiser@livjm.ac.uk>
To: cambridge-conference <cambridge-conference@livjm.ac.uk>
Subject: CCNet 19/2001 - 2 February 2001
Date: Fri, 2 Feb 2001 12:30:01 -0000 

CCNet 19/2001 - 2 February 2001
-------------------------------

(1) METEORITE NARROWLY MISSES EARTH [???]
    DPA (German Press Agency), 25 January 2001

[...]

(7) ESTIMATING TOTAL MASS OF COMET POPULATION STILL A MAJOR PROBLEM
    Lubos Neslusan <ne@ta3.sk>

[...]

========================================================================

(1) METEORITE NARROWLY MISSES EARTH

>From DPA (German Press Agency), 25 January 2001
http://www.rp-online.de/news/wissenschaft/2001-0125/meteor.html ...

[English translation immediately follows...]

Meteorit raste knapp an der Erde vorbei

Cambridge (dpa). In einem Abstand von nur rund 300.000 Kilometern ist Mitte
Januar ein etwa 30 Meter grosser Brocken an der Erde vorbeigerast. Dies
meldete das Minor Planet Center der Internationalen Astronomischen Union in
Cambridge (Massachusetts) am Mittwochabend.

Das Objekt mit der vorlaeufigen Bezeichnung 2001 BA 16 sei allerdings erst
drei Tage nach der groessten Annaeherung am 16. Januar von Astronomen der
Lincoln Laboratories in New Mexico entdeckt worden. Bei einem Zusammenstoss
mit der Erde waere es zu einem spektakulaeren Meteoritenhagel gekommen.

Gesteinsbrocken von weniger als 60 Metern Durchmesser werden auf dem Weg
durch die Atmosphaere in der Regel von den auftretenden Kraeften zertroemmert.
Das AusmassF moeglicher Schaeden haengt von der Groesse der Einzelbrocken und
dem Aufschlagort ab. Es ist daher nicht bekannt welche Schaeden dieser
Meteoritenhagel ausgeloest haette.

Copyright 2001, dpa
-------------
METEORITE NARROWLY MISSES EARTH

A chunk of rock some 30 metres across shaved the earth by a distance of
300,000 km in mid January. This was reported on Wednesday evening (Jan. 24)
by the Minor Planet Centre of the International Astronomical Union in
Cambridge Massachusetts. The object with the temporary designation 2001
BA16, however, was said to be discovered by astronomers of the Lincoln
Laboratries in New Mexico only three days after its closest approach on
January 16. A collision with Earth would have resulted in a spectacular
meterorite shower.

Chunks of rock smaller than 60 metres in diametre and travelling through the
atmopshere are smashed up, as a rule, by occurring forces. The level of
possible damage depends on the size of individual rocks and the location of
impact. Consequently, it is unknown what damage such a meteorite shower
would have triggered.

========================================================================
* LETTERS TO THE MODERATOR *
========================================================================

(7) ESTIMATING TOTAL MASS OF COMET POPULATION STILL A MAJOR PROBLEM

>From Lubos Neslusan <ne@ta3.sk>

currently affiliated at:
   Queen Mary and Westfield College
   University of London
   Mile End Road
   London, E1 4NS

It seems to be worthy to add a short comment to the finding of comet =
cloud
mass reduction by American astronomers, Dr. Paul Weismann and Dr. Alan
Stern, reported in CCNet (18/2001).

The most recent previous estimate of the total mass of the CURRENT Oort
cloud by Weismann (1995) was about 34 Me (Earth masses). The older =
estimates
were even higher (45-50 Me by Weismann in 1990; at least 380 Me by Mark
Bailey in 1994). As the INITIAL mass of Oort cloud (i.e. the mass in =
time of
its creation) had to be larger by a factor of 2 to 5, it is clear that =
this
mass significantly exceeded the sum of the masses of Uranus and =
Neptune,
which were assumed as the main ejectors of comets into the cloud. The =
law of
energy conservation, however, does not permit the ejection of such =
large
masses. The primordial concept of comet origin, assuming the creation =
of
these in the outskirts of the protoplanetary disc and their subsequent
planetary ejection in large distances, would thus be invalid.

This problem arising from the lack of sufficiant energy is serious =
enough to
look for alternative explanations regarding the origin of comets. The =
most
recent alternative attempt was published last year (Neslusan L.: 2000, =
`The
Oort cloud as a remnant of the protosolar nebula', Astron. Astrophys. =
361,
369-378). According to this new concept, the common birth-place of =
comets
are the cool, dense, inter-stellar molecular clouds (an idea that has =
been
suggested several times by other theories), most probably in the =
beginning
of star formation. This assumption yields that the cometary nuclei had =
to be
present also in the protosolar nebula already before its collapse into
protosun and protoplanetary disc. Whilst the gaseous and (microsopic) =
dusty
components of nebula collapsed by the laws of hydrodynamics, the =
macroscopic
bodies, as cometary nuclei, took part in the collapse in a different =
way
and, as was demonstrated, remained at large nebula-centric distances.

New determinantions of sizes of cometary nuclei coming from the Oort cloud
can, however, still support the primordial concept, if they show that the
mass of a typical Oort cloud comet is smaller or, at least, not larger
than the new estimates by Weissman and Stern.

Lubos Neslusan

--------------------------------------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)=20
--------------------------------------------------------------------
The CCNet is a scholarly electronic network. To subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information circulated on this network is for scholarly and educational
use only. The attached information may not be copied or reproduced for
any other purposes without prior permission of the copyright holders.
The fully indexed archive of the CCNet, from February 1997 on, can be
found at: http://abob.libs.uga.edu/bobk/cccmenu.html

DISCLAIMER: The opinions, beliefs and viewpoints expressed in the
articles and texts and in other CCNet contributions do not necessarily
reflect the opinions, beliefs and viewpoints of the moderator of this
network.

------- End of Forwarded Message