PLEASE NOTE:
*
CCNet 19/2001 - 2 February 2001
-------------------------------
"Almost without exception extra-solar planetary systems
differ
significantly from the solar system in terms of their dynamic
configurations, size, and the radial distribution of their
planets. On
the basis of these discoveries our solar system can no longer be
regarded as
a reference standard for the formation and configuration of
planetary
systems."
--Richard L.S. Taylor, Probability Research Group, 1
February 2001
"The debate over what to call Pluto is a red herring. It is
not the
heart of the problem, it is a symptom. The problem is that we do
not have
a definition of "planet", pure and simple. Major,
minor, comet,
asteroid, KBO... these are labels we have stuck on these objects
without a clear idea of what they mean."
--Phil Plait, The Bad Astronomer, 1 February 2001
"Let's reclassify Pluto as a Mickey Mouse planet."
--Gerrit Verschuur, Memphis University, 1 February 2001
(1) METEORITE NARROWLY MISSES EARTH
DPA (German Press Agency), 25 January 2001
(2) PLANETS WITHOUT STARS
Richard L.S. Taylor <probability.rgroup@virgin.net>
(3) THE FUTURE OF LIMITLESS ENERGY SUPPLIES: JAPAN PLANS ORBITING
SOLAR
POWER STATION
SpaceDaily, 1 February 2001
(4) DISASTER MANAGEMENT WORKING PAPAERS
John Twigg <j.twigg@UCL.AC.UK>
(5) CELEBRATING BRITAIN IN SPACE
Dave Wright <L.F.Wright@livjm.ac.uk>
(6) ASTEROIDS 2001: SECOND ANNOUNCEMENT
Donata Randazzo & Laura Daricello <ceres2001@oapa.astropa.unipa.it
>
(7) ESTIMATING TOTAL MASS OF COMET POPULATION STILL A MAJOR
PROBLEM
Lubos Neslusan <ne@ta3.sk>
(8) IS OUR SOLAR SYSTEM NOMENCLATURE IN CRISIS?
Phil Plait <badastro@badastronomy.com>
(9) PLUTO AND CHARON: BINARY PLANETS?
Michael Paine <mpaine@tpgi.com.au>
=================
(1) METEORITE NARROWLY MISSES EARTH
From DPA (German Press Agency), 25 January 2001
http://www.rp-online.de/news/wissenschaft/2001-0125/meteor.html
...
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 vorläufigen Bezeichnung 2001 BA 16 sei
allerdings erst
drei Tage nach der größten Annäherung am 16. Januar von
Astronomen der
Lincoln Laboratories in New Mexico entdeckt worden. Bei einem
Zusammenstoß
mit der Erde wäre es zu einem spektakulären Meteoritenhagel
gekommen.
Gesteinsbrocken von weniger als 60 Metern Durchmesser werden auf
dem Weg
durch die Atmosphäre in der Regel von den auftretenden Kräften
zertrümmert.
Das Ausmaß möglicher Schäden hängt von der Größe der
Einzelbrocken und dem
Aufschlagort ab. Es ist daher nicht bekannt welche Schäden
dieser
Meteoritenhagel ausgelöst hätte.
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.
===========
(2) PLANETS WITHOUT STARS
From Richard L.S. Taylor <probability.rgroup@virgin.net>,
Probability
Research Group. UK
Early in 2000 Lucas and Roche reported the discovery of a
population of very
young brown dwarfs and free-floating planets the Trapezium
cluster in Orion.
The results were obtained using the UKIRT high-resolution UFTI
camera. Only
a few weeks later three other teams of astronomers (two American,
one
Spanish) also announced the detection of young isolated planetary
mass
objects (IPMOs) in other star forming regions (SFRs). Together
these
observations may indicate that the majority of bodies of
mass ~3 to ~80
MJup may not be associated with stars but form
independently, or in a
smaller number of cases have been ejected from gravitationally
bound systems
to become UBOs (un-bound objects). Many of these objects appear
to have a
mass at and below the deuterium fusion limiting mass of ~13MJup
and hence
can be classified as planets. The number of such objects in the
galaxy is as
yet unknown but may exceed, by orders of magnitude, the total
number of
stars in the Galaxy.
The idea that planets might exist that are not bound from stars
was proposed
first by Opik in 1964, and discussed in detail in 1989 by Fogg.
In a 1990
Fogg argued that ISPs were of two basic types: those formed as
solitary
objects within molecular clouds and those formed within, and
subsequently
unbound from, planetary systems. In the early 1990s the discovery
and study
of circum-stellar disks associated with YSOs (Young Stellar
Objects) forming
in molecular clouds, together with the discovery of
protoplanetary disks,
led to the idea that many stars may be accompanied by planets.
The search
for other solar systems, which had begun with the search for
unseen low mass
stellar companions in the 1940s, but which lacking success had
remained
dormant since the mid-70s, re-gathered momentum in 1995 after
Mayor and
Queloz discovered a Jupiter-mass companion to a solar-like
star.
Progress since then has been rapid and at the time of writing ~46
stars are
known to be accompanied by a planet or planets and a further 12
have brown
dwarf companions above the deuterium fusion mass limit of ~13
Jupiter
masses. The smallest mass of any planet orbiting a main sequence
star so far
discovered is ~0.16 MJup. However, almost without exception
extra-solar
planetary systems differ significantly from the solar system in
terms of
their dynamic configurations, size, and the radial
distribution of their
planets. On the basis of these discoveries our solar system can
no longer be
regarded as a reference standard for the formation and
configuration of
planetary systems.
The distribution of mass and the high eccentricity of planetary
orbits
within many of the extra-solar planetary systems suggests that a
significant
level of gravitational interaction has taken place within them.
The very
small radius orbits occupied by ~Jupiter-mass gas-giant planets
in some
systems are now explained generally in terms of complex giant
planet -
protoplanetary disk interactions. These lead to inward migration
of large
protoplanet(s). The breaking mechanism that has prevented the
loss, through
coalesence with the central star, of inwardly migrating planets
is a problem
that has a number of possible solutions and these continue to be
studied.
Chaos resulting from gravitational interactions between
extra-solar planets
migrating to increasingly small radius orbits can result in some
being
perturbed into orbits of high eccentricity. Such perturbative
interactions
cumulatively may lead to the gravitational ejection of planets
from the
gravitational control of their primary star, hurling them into
interstellar
space to form an unbound planet, a UBPO. The question is whether
the number
of IPMOs discovered within SFRs can be accounted for on the basis
of the
number and age of planets expected to ejected from extra-solar
systems or
whether isolated, that is solitary, formation is the predominant
mode of
origin of ISPs. The latter possibility raises the whole question
of the
number of very low mass and substellar objects (i.e. planets)
that may form
in the galaxy.
The number density of low mass objects, brown dwarfs and ISPs,
objects that
are small dim and hard to detect, is strongly dependant on the
ISMF (initial
stellar mass function). The lowest mass of a main sequence star,
a body
capable of sustaining the thermonuclear burning of hydrogen, is
~0.08M.
Below this limit the fusion of normal hydrogen is not possible
but the much
scarcer isotope deuterium can provide a short lived and much
lower output of
thermonuclear energy down to a mass limit about six and a half
times smaller
~0.012M : i.e. ~13MJup. The important question is if
the stellar
mass function (SMF) continues on downwards for VLM objects to and
below the
H and D thermonuclear reaction limits. That is whether the
mass function
links brown dwarfs and ISPs (we arbitarily define ISPs as bodies
with a mass
range ~ 3 13MJup) into a single power law relationship.
Although M-Type stars are the most abundant Main-Sequence objects
until 1998
it was widely believed that the SMF turned downed very sharply,
or even
ceased to hold below ~0.1M. The possibility that objects
might exist at and
below the hydrogen burning limit of 0.08M was proposed by Kumar
in 1963. The
first identification of a brown dwarf star was announced, in
1985,
independently, by McCarthy (University of Arizona), and
Harrington et al,
(US Naval Observatory). Although this first discovery was
soon followed by
other similar examples of brown dwarf companions, the rate of
discovery was
relatively slow. The first field, that is solitary, free-floating
brown
dwarf was found in 1996 about 30 ly distant from the Sun, its
estimated mass
is <75Mjup).
In 1997 brown dwarfs, were still regarded as being rare and were
reported as
such at conferences. This paucity of brown dwarf discoveries
seemed to show
that the SMF did not continue to such low-masses. However, the
ongoing
advance in detection techniques and imaging systems has led to
more and more
examples of VLM objects being discovered. Searches in stellar
nurseries are
yielding increasingly successful results. In 1998 Tamura et al.,
reported a
study of isolated and companion young very young brown dwarfs
(age ~106
years) in the Taurus and Chamaeleon Molecular Clouds.
In 1986 Boss concluded that the minimum protostellar mass
was 0.02M and
thus the formation of brown dwarf stars is consistent with the
theory of
hierarchial protostellar fragmentation. This implied that
formation of
objects with masses <0.02M - about 20 Jupiter
masses - could not proceed
from the fragmentation of interstellar clouds, and that such
objects must
therefore begin their life as bound planets, forming within a a
circumstellar disk through processes such as accumulation or
gravitational
instability. More recent work has led Boss to revise this limit
downwards to
~3MJup.
Recent surveys of other young star clusters indicate that
low-mass objects
are common. Najita et al., National Optical Astronomical
Observatories,
Tucson, Arizona, using HST/NICMOS were able to make a complete
study to very
low masses in the Young Cluster IC 348 (mass range 0.7 to
0.015M). From
their observations Najita, et al, believe that it is possible to
say that
for low-mass objects the initial stellar mass function shows no
sign of
falling off with reducing mass.believe that the SMF may extend
down to
masses 3MJup. Thus the formation process that produces
stars seems to be
equally capable of forming low mass objects as stars. If true
this could
raise the stellar number density by a factor of anything up to
~105.
Fogg suggested in 1990 the best guess that could be made for the
number
density of unbound planets, ISPs, in the solar neighbourhood was
Nisp > 0.1
pc-3 but this would now appear likely to be an under-estimate.
Although he
proposed four potential mechanisms through which planets could
become
unbound from their primary star - two from fully developed
planetary systems
(Late Type) and two from the early stages of circumstellar
formation (Early
Type). Three of these mechanisms have far too low probability to
account for
the apparent number density of very low-mass objects now being
discovered.
The remaining mechanism is only capable of accounting for numbers
of unbound
planets at or below the lower limit of current observations. This
implies
that the the majority of ISPs have their origin as IPMOs, they
are 'Field
Planets' rather than representative of the far smaller number
planets
unbound from their primary star. Such escapees will be expected
to have
masses around or below ~3MJup.
As one, or several ISPs should lie significantly closer to the
solar system
than the nearest star - within an average distance of the Sun of
a few
tenths of a light year - it may be that the perturbation of
comets from the
Oort Cloud and the Kuiper Belt, and the large departure from the
plane of
the ecliptic of many of outer solar system orbits may be
attribituable to
the close passage of ISPs.
The detection of isolated bodies of planetary mass 13MJup
IPMOs/ISPs is
demanding and to date the lowest mass objects discovered are
between 5MJup
8MJup. These have ages between 2 to 5 million years and it is
possible that
bodies of smaller mass of within this age band, leave alone those
of greater
age, will have cooled sufficiently to take them below our present
threshold
of detection. However, it is possible that indirect
evidence for the
proximity or the close passage of ISPs to the Sun exists.
Recently Murray
(UCL) presented arguments for the presence of a distant
large undiscovered
solar system planet. These were based on the observation
that the aphelion
distances of long-period comets show a slight excess around
30,000 to 50,000
au from the Sun.
Murray suggests that one possible explanation for this non-random
clustering
is that it is due to orbital perturbations by an undiscovered
object
orbiting within the 30,000 to 50,000 au distance range, and
describes a
model consistent with the observations gives a retrograde orbit
(inclination
120o) radius of 32 000 au for the object with a period of
5.8 x 106 yr.
Collander-Brown, et al., (QM&WC) however investigated the
orbital evolution
of both real and hypothetical Edgeworth-Kuiper Objects in order
to determine
whether any conclusions can be drawn regarding the existence of
the planet
postulated by Murray. They conclude that the hypothetical
planet has been
placed on an orbit at such a large heliocentric distance that no
evidence
for its existence, or non-existence, can be found from a study of
the known
Edgeworth-Kuiper Objects.
The distances of 30,000 and 50,000 au determined by Murray are
close to the
postulated mean distances, separating the closest ISPs from the
Sun, for the
upper abundance of ISPs. However, both Murray and Collander-Brown
are
assuming an object in orbit around the Sun and the possibility
that the
perturbation(s) have resulted from the close approach and passage
of one or
more ISPs has yet to be given consideration.
As an IPMOs/ISPs cools it can be expected to develop a
structurally
differentiated interior. For a planetary mass of stellar
composition the
core size will be relatively smaller than in a H, He, depleted
planet like
Jupiter. The much higher gravity and hence gravitational
compression make
the interior structure and physical conditions within an ISP
differ from
those within the deep interiors of solar system gas giants.
Unlike star-bound planets ISPs have no external heat source but
as the radii
of ISPs within the mass range ~3MJup ~13MJup will not
differ significantly
from RJup the heat flow m-2 within an ISPs with an age
similar to that of
Jupiter will to a first approximation be proportional to its
mass. The
nature of these super-planets suggests an inner core that is
overlain by a
deep ocean and atmosphere consisting chiefly of H and He, but
containing
methane and other hydrocarbons, ammonia, sulfur compounds as well
as many
other trace materials.
The organic molecular content of the atmosphere, the possible
presence of a
substantial cis-global open or partially or completely ice-capped
ocean, and
the pressure and temperature gradients expected to be present
provide
potential ecozones of great size for extremophile microbial life.
It is
entirely possible that some equivalent of ocean-floor smokers
could provide
the energy and chemical input necessary for quite complex forms
of
autotrophic life. As the cooling time of planetary mass ISPs is
longer than
present age of the universe ISPs may possibly be the most
widespread life
bearing planets - number of living worlds could be ~1011 or
greater.
If the number of <13MJup bodies is close to the possible upper
bound the
nearest ISP should lie ~10 times closer than the nearest star. If
one or
more ISPs could be detected at such cosmically small distances
they would
constitute important nearby targets for the first step in to
extra-solar-system space exploration. There are many reasons why
it would be
valuable to examine such bodies close up. The main hurdle that
has to be
overcome is to tackle the problem of detection of these
relatively small
diameter cool objects T ~300K. A microwave and/or far
infrared whole sky
map might reveal 'hot-spots' that coincide with no known objects.
Once
identified more detailed study of their motion as well as the
application of
sensitive imaging techniques may reveal them.
To sum up: the prescience of Opik and Fogg seems now to have been
vindicated
by observational data of IPMOs, the discovery of extra-solar
planetary
systems, and the improved understanding of the SMF. On the basis
of current
data it seems likely that the great majority of ISPs are likely
to have
formed as isolated objects - as Field Planets - in SFRs and only
a far
smaller number will be unbound planets.
The bulk composition of IPMOs and unbound planets are likely to
differ
systematically. Unbound planets will be expected to show H, He,
depletion
relative to bulk stellar composition. IPMOs/ISPs formed in
isolation will
closely match bulk stellar composition for the SFR where they
have formed.
The total number of IPMOs/ISPs may be very large. Several times
1011 to as
many as ~1013 such objects may exist in the galaxy. Their
distribution
pattern will match that of stars and therefore one or more such
objects
should lie very close to the Sun. Computational study of
the pattern of
perturbations of Oort Cloud objects back over a significant
number of
orbital cycles may provide evidence for the close fly-by of an
ISP object.
If ISPs exist in vast numbers then many of them will be older as
well as
comparable in age with solar system planets. Some of these
objects may have
supported, or may support, forms of autotrophic extremophile
life. They
could constitute the largest environment for life in the galaxy
and perhaps
in the entire universe.
[Extracted from: Taylor, R.L.S., "Planets Without
Stars: The probable
abundance, nature and significance of ISPs." JBIS, 54,
19-26, (2001).
Electronic PDF format reprint available on request from
probability.rgroup@virgin.net
]
Principal References
Boss, A.P., Theoretical Determination of the Minimum Protostellar
Mass, In
'Astrophysics of Brown Dwarfs', Eds. M.C Kafatos, R.S.
Harrington, S.P.
Maran, Cambridge U.P. (1986) also Science, 276, 1836, (1997)
&
'Looking for Earths' John Wiley, New York, (1998)
Collander-Brown, S., et al., Mon.Not.R.Astr.Soc., 318, 101-108¸
(2000)
Fogg, M.J., Earth, Moon & Planets, 43, 123, (1989) and
Comments Astrophys,
14, 357, (1990)
Harrington, R.S. et al., Ap.J, 88, 1038, (1983) and Harrington,
R.S.,
B.A.A.S. 17, 624 (1985)
Kumar, S.S. 'Planetary Systems', in 'The Emerging
Universe', eds W.C.
Saslaw & K.C. Jacobs, University of Virginia Press,
Charlottsville, (1972)
Lucas, P. W. and Roche P. F., Mon.Not.R.Astr.Soc. 314, 858¸
(2000)
McCarthy, D.W., 'Infrared Speckle Interferometry: A sensitive
Technique for
Physical Measurements of Unseen Companions to Nearby stars', In
Astrometric Techniques, Ed. Eichhorn, (1984)
Marcy, G.W., and Benitz, K.J., ApJ., 464, L147, (1996) and
Marcy, G.W., et
al., ApJ., 481, 926, (1997)
Mayor, M., and Queloz, D., Nature, 378, 355, (1995)
Murray, J. B., Mon.Not.R.Astr.Soc. 309, 31¸ (2000)
Najita J., et al., ApJ, 541, (2000)
Opik E. J,, Irish Astron.J., 6, 296 (1964).
Tamura, M., et al., Science, 282, 1095, (1998)
Zapatero-Osorio, et al., Astron.Astrophys. 317, 164-170,
(1997) &
Zapatero-Osorio, M. R., et al., Science, 290, 103
(2000)
==========
(3) THE FUTURE OF LIMITLESS ENERGY SUPPLIES: JAPAN PLANS ORBITING
SOLAR
POWER STATION
From SpaceDaily, 1 February 2001
http://www.spacedaily.com/news/japan-meti-space-01a.html
Japan Plans To Launch Solar Power Station In Space By 2040
by Takahiro Fukada
Tokyo (AFP) Jan. 31, 2001
Undaunted by its less than glorious track record in space,
Japan's ministry
of economy, trade and industry (METI) has ambitious plans to
launch a giant
solar power station by 2040. "We are starting research for a
solar power
generation satellite from fiscal year 2001 in April," Osamu
Takenouchi, of
METI's airplane, weapons and space industry division told AFP.
"We are planning to start operating the system in
2040," Takenouchi added.
"On Earth, clouds absorb sunlight, reducing (solar) power
generation. But in
space, we will be able to generate electric power even at
night," Takenouchi
said.
METI plans to launch a satellite capable of generating one
million kilowatts
per second -- equivalent to the output of a nuclear plant -- into
geostationary orbit, about 36,000 kilometers (22,320 miles) above
the
earth's surface.
The satellite will have two gigantic solar power-generating wing
panels,
each measuring three kilometers by a 1,000 meter diameter power
transmission
antenna between them, Takenouchi said.
The electricity produced will be sent back to earth in the form
of
microwaves with a lower intensity than those emitted by mobile
phones.
"We intend to ensure the microwaves will not interrupt
mobile phone and
other telecommunications," Takenouchi said.
The receiving antenna on the ground, several kilometers in
diameter, would
probably be set up in a desert or at sea, and the electricity
relayed from
there along conventional cables he said.
The satellite is projected to weigh about 20,000 tonnes and the
total
construction cost is estimated at around two trillion yen (17
billion
dollars), at current prices.
One economic hurdle so far is that it would cost about 23 yen per
kilowatt
hour to generate power in space compared to nine yen for thermal
or nuclear
power generation.
"But we will consider ways to lower the costs,"
Takenouchi said.
A similar plan was aired by the United States' National
Aeronautics and
Space Administration (NASA) but nothing has so far come of it.
One of the reasons for pursuing the dream of beaming power back
to Earth is
that scientists believe it could help reduce global warming.
"Solar power generation will not emit carbon dioxide, and so
would benefit
the environment compared to thermal power," Takenouchi said.
Besides, "the safety and other issues associated with
nuclear power
generation will disappear," Takenouchi said.
Honorary professor of space science at Tokyo University, Jun
Nishimura said
launching such a huge satellite was theoretically possible,
adding the
investment on research and development was money well spent.
Satellites being put into orbit nowadays weigh between 20 and 30
tonnes on
average, Nishimura noted. "But 20 to 30 years earlier,
satellites weighing
only 100 kilograms could be launched."
"The International Space Station will also be huge."
While the lead time needed to develop the technology to build
large-scale
structures in space made 2040 a realistic target date, "the
real question is
cost performance," he said.
"Solar power generation in space can be realized only if the
same amount of
electricity can be generated at the same cost" as
conventional means of
power generation including construction costs, Nishimura said.
Japan started its space development programme in 1969 and has
launched more
than 30 rockets. But the programme has been blighted by a series
of
embarrassing failures.
Last November, the National Space Development Agency of Japan was
forced to
explode an H-2 rocket and satellite by remote control when it
veered off
course after lift-off.
In February 1998, a satellite was lost in space despite a
successful
separation from an H-2 rocket because it was released at the
wrong altitude
and sent into an elliptical orbit.
The H-2 is intended to be Japan's answer to Europe's Ariane
commercial
satellite launch vehicle.
Editor's Note: METI is the new name for what was formerly the
Ministery of
International Trade and Industry - the all powerful MITI.
All rights reserved. © 2001 Agence France-Presse.
===========
(4) DISASTER MANAGEMENT WORKING PAPAERS
From John Twigg <j.twigg@UCL.AC.UK>
The Benfield Greig Hazard Research Centre at University College
London is
launching a series of Disaster Management Working Papers.
The series is designed to make new evidence, analysis and ideas
available to
researchers and practitioners worldwide. Five main categories are
envisaged:
research papers, case studies, field notes, discussion papers,
and
guidelines and training materials.
The first Working Paper has been issued. It is a discussion paper
entitled
'Physician heal thyself? The politics of disaster
mitigation', by John
Twigg. The paper looks at some of the reasons why so little
is being done
to reduce people's vulnerability to natural disasters, and
suggests that
part of the problem lies within the so-called disaster
'community' and is
political, in the broadest sense of the word.
The Working Paper can be downloaded from the Benfield Greig
Hazard Research
Centre's website (http://www.bghrc.com
- go to the site's Disaster
Management page). Further papers in the series will appear in due
course.
===============
(5) CELEBRATING BRITAIN IN SPACE
From Dave Wright <L.F.Wright@livjm.ac.uk>
IT'S ROCKET SCIENCE: THE BROHP ANNUAL CONFERENCE at Charterhouse
School
(Godalming Surrey)
Sponsored by BIS and Supported by BNSC
CELEBRATING BRITAIN IN SPACE
April 12, 13 and 14th 2001
Contributions will include
Director General of BNSC Colin Hicks
Prof John Allen who will propose a toast to Yuri Gagarin on April
12th and
talk about the Advanced Projects Group at HSD, Charles Martin
Eur. Eng. on
ELDO B, Prof McInnes on Solar Sails, David Ashford on Ascender,
Dr John
Becklake on The German contribution, Derek Bollworthy running a
Trials team,
Ian Coxhill on the work of SSTL, Roy Dommett CBE on Blue Streak,
Captain
Eric (Winkle) Brown, Dr. John Griffiths Science Museum on work of
Lubbock
and Gollin, Tom Griffiths on Aberporth, John Harlow on flights
that didn't
quite go to plan, Andy Jeffs on The Beta engine, Keith Hayward
from SBAC on
The Future of the British Aerospace Industry, Dr Barrie Ricketson
on
Hydrogen Propulsion, Dick Stratton, Jay Tate Spaceguard on Near
Earth
Objects, Wayne Cocroft on Industrial Archaeology, Bruce White on
Black
Arrow.
There will be numerous other contributions celebrating the
achievments of
British Engineers and Scientists from Beagle II and the present
day back to
the 1940's. A chance to rub shoulders with the cream of British
Aerospace
Engineers and Scientists. The cost of attendance is £120 but
£99 to BIS
members. This is for three days fully residential attendance plus
conference
dinner. Cheques payable to BROHP, Places will be limited.
For further details go to the Conference web site at
http://members.aol.com/nicholashl/ukspace/ukspace.htm
or write to Dave Wright, 17 Elsmere Ave., Aigburth, Liverpool, L
17 4LB
BROHP2@aol.com or phone
0151-281-1134
A small number of places are available to students free thanks to
BNSC!
Would your firm or organisation sponsor a student to attend?
Missed Rio?
Come to sunny Surrey!
============
(6) ASTEROIDS 2001: SECOND ANNOUNCEMENT
From Donata Randazzo & Laura Daricello <ceres2001@oapa.astropa.unipa.it
>
ASTEROIDS 2001: From Piazzi to the 3rd Millennium
Santa Flavia, Palermo, 11-16 June 2001
SECOND ANNOUNCEMENT
www.astropa.unipa.it/Asteroids2001/index1.html
GENERAL INFORMATION
The international conference "Asteroids 2001: from Piazzi to
the 3rd
Millennium" will be held in Santa Flavia (Palermo) from 11
to 16 June 2001.
The conference aims to present the current understanding of
asteroid
science. Invited reviews, contributed papers, and poster papers
will be
presented. In addition, Asteroids 2001 will bring together
authors for the
Space Science Series book "Asteroids III", that will be
published by the
University of Arizona Press. The conference is organized by
Osservatorio
Astronomico di Palermo G.S. Vaiana, Dipartimento di Scienze
Fisiche e
Astronomiche dell'Universita' di Palermo, Dipartimento di Fisica
e
Astronomia dell'Universita' di Catania, Osservatorio Astrofisico
di Catania
and Osservatorio Astronomico di Torino as part of the
celebrations of the
200th anniversary of Giuseppe Piazzi's discovery of 1 Ceres from
the tower
of Palermo Observatory on January 1st 1801.
Registration and attendance at the Asteroids 2001 conference is
open only to
professionals in astronomy, planetary science, and their
students.
SCIENTIFIC PROGRAMME
Topics to be discussed at the conference include:
1. History
2. Ground-based observations: techniques and reports of results
3. Space-based observations
4. Composition and physical structure
5. Asteroid families and collisional processes
6. Interrelationships with inner SS objects: Near-Earth Objects,
Meteorites,
Meteor streams
7. Interrelationships with outer SS objects: Trojans, Centaurs,
Edgeworth-Kuiper objects, Comets
8. Dynamical structure
9. Inventory, origin, evolution, etc.
The above scientific programme will include two daily sessions.
Morning
sessions, except the opening one, will typically include 2
invited reviews
and 9 contributed papers, afternoon sessions will typically
include 2
invited reviews and 7 contributed papers. Contributions for oral
presentation will be selected by the SOC on the basis of the
submitted
abstracts.
Invited talks will be 25 minutes in length plus 15 minutes for
discussion.
Contributed talks will be 10 minutes in length plus 5 minutes for
discussion. Presenters will be asked to carefully honour their
assigned
time. Authors will be notified in due time if their contribution
is
scheduled as an oral or poster presentation. The preliminary
scientific
programme will be available on the web after April 10th.
=============================
* 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
============
(8) IS OUR SOLAR SYSTEM NOMENCLATURE IN CRISIS?
From Phil Plait <badastro@badastronomy.com>
Hi Benny--
Well, what a mess we have on our hands now, eh? The Pluto
"debate" in CCNet
is now a mish-mash of opinions, with only dimly heard calls for
reason. I
have been in too many arguments like this!
The debate over what to call Pluto is a red herring. It is not
the heart of
the problem, it is a symptom. The problem is that we do not have
a
definition of "planet", pure and simple. Major, minor,
comet, asteroid,
KBO... these are labels we have stuck on these objects without a
clear idea
of what they mean.
I strongly urge the readers of this email list to read the paper
by Alan
Stern and Hal Levison about redefining what is meant by
"planet". Although
humorously written, the paper makes several salient points about
our current
(lack of a) definition, including strengths and weaknesses. The
paper is
available in PostScript form on Alan Stern's website at
http://www.boulder.swri.edu/alan/papers.html
and is titled: "Regarding the
criteria for planethood and proposed classification
schemes".
This may not end the debate, but it will hopefully give everyone
a place to
start having a rational discussion.
My own opinion: emotion plays a part in this, but it must be
relegated to a
personal level and not be used as a debating tool! I believe
Pluto should
not be a "major" planet, and it will be odd and vaguely
sad to see it taken
off whatever lists we keep of such things. But I will not let my
discomfort
stand in the way of my reason. Things change as our knowledge
grows, and it
is not just important but *vital* to a a scientist not to be
married
irrevocably to any one idea.
* * *
* * The Bad
Astronomer *
* * *
Phil
Plait
badastro@badastronomy.com
The Bad Astronomy Web Page: http://www.badastronomy.com
============
(9) PLUTO AND CHARON: BINARY PLANETS?
From Michael Paine <mpaine@tpgi.com.au>
Dear Benny,
As I indicated in my essay of 25 Sep 2000
(http://abob.libs.uga.edu/bobk/ccc/ce092500.html
)
I support the use of physical size to define a (major) planet.
1000km
diameter seems appropriate (it may be arbitrary but a line has to
be drawn
somewhere). That would fix the uncertain status of Pluto but it
does lead to
an interesting problem - the status of Charon, which is about
1200km in
diameter. It it a moon of Pluto or a planet in its own right? My
preference
(for reasons given in my essay) is to regard Pluto and Charon as
a binary
planet. Do we then credit Clyde Tombaugh with discovering the
first binary
planet or the ninth AND tenth planets? Or does credit for
discovering the
tenth planet (Charon) go to James W. Christy and Robert S.
Harrington at the
U.S. Naval Observatory in Flagstaff, Arizona?
I only wish the fantastic scientific discoveries that are being
made about
objects in our solar system received as much attention in the
general press
as the fuss over Pluto's status.
regards
Michael Paine
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*
OPEN LETTER TO READERS OF CCNet
From Neil de Grasse Tyson <tyson@astro.amnh.org>
Regarding our exhibits in New York City's new Rose Center for
Earth
and Space, I am surprised and impressed by the amount of recent
media
attention triggered by our decision to treat Pluto differently
from
the other planets in the solar system
I am surprised because our exhibit has been in place since
opening
day, 19 February 2000, and our treatment didn't seem to be
newsworthy
at the time. I am impressed that people feel so strongly about
Pluto
that much time and attention had been devoted to it in print and
on
the air.
The New York Times' front page article, which ignited the recent
firestorm, donned a title that was somewhat afield of what we
actually did, and which I would like to clarify. The title
read
"Pluto not a Planet? Only in New York", which implied
that we kicked
Pluto out of the solar system and that we are alone in this
action
and that, perhaps more humorously, Pluto wasn't big enough to
make it
in NYC.
I have written previously on the subject, in an essay titled
"Pluto's
Honor" (Natural History magazine February 1999) where I
review how
the classification of "planet" in our solar system has
changed many
times, most notably with the 1801 discovery of the first of many
new
planets in orbit between Mars and Jupiter. These new planets, of
course, later became known as asteroids. In the essay, arguing in
part by analogy with the asteroids belt, I argued strongly that
Pluto, being half ice by volume, should assume its rightful
status as
the King of the Kuiper belt of comets. Apart from my views
expressed
there, I have a different sort of responsibility to the public as
director of the Hayden Planetarium and as project scientist of
the
Rose Center for Earth & Space.
That responsibility is as an educator for a facility that has
received an average of 1,000 people per *hour* over the past
eleven
months. For the exhibit on planets in our "Hall of the
Universe",
rather than use the word planet as a classifier, we essentially
abandon the ill-defined concept and simply group together
families
of like-objects. In other words, instead of counting
planets or
declaring what is a planet and what is not, we organize the
objects
of the solar system into five broad families: the terrestrial
planets, the asteroid belt, the Jovian planets, the Kuiper belt,
and
the Oort cloud. With this approach, numbers do not matter and
memorized facts about planets do not matter. What matters is an
understanding of the structure and layout of the solar system. On
other panels, in an exercise in comparative planetology, we
highlight
rings, storms, the greenhouse effect, surface features, and
orbits
with discussions that draw from all members of the solar system
where
interesting and relevant.
Our intro-exhibit panel meets the visitor's expectations head-on:
------------------
"What is a planet?"
"In our solar system, planets are the major bodies orbiting
the Sun.
Because we cannot yet observe other planetary systems in similar
detail, a universal definition of a planet has not emerged. In
general, planets are massive enough for their gravity to make
them
spherical, but small enough to avoid nuclear fusion in their
cores."
------------------
A second panel, describes and depicts the layout of the solar
system:
-----------------
"Our Planetary System"
Five classes of objects orbit our Sun. The inner
*terrestrial
planets* are separated from the outer *gas giant* planets by the
*asteroid belt*. Beyond the outer planets is the *Kuiper
Belt* of
comets, a disk of small icy worlds including Pluto. Much more
distant, reaching a thousand times farther than Pluto, lies the
*Oort
Cloud* of comets."
-----------------
Our goal was to get teachers, students, and the average visitor
to
leave our facility thinking about the solar system as a landscape
of
families rather than as an exercise in mnemonic recitation of
planet
sequences.
That being said, I have benefited from some reasoned feedback on
what
we have done. As many are already aware, we use our giant 87-foot
sphere (housing the Hayden Space Theater in the upper half and a
recreation of the first three minutes of the Big bang in the
lower
half) as an exhibit unto itself. We invoke it to compare the
relative
sizes of things in the universe for a walkaround "powers of
ten"
journey that descends from the observable universe all the way to
atomic nuclei. About midway in the journey you come upon the size
scale where the sphere represents the Sun. On that scale,
hanging
from the ceiling, are the Jovian planets (the most highly
photographed spot in the facility) while a set of four small orbs
are
also on view, attached to the railing. These are the terrestrial
planets. No other members of the solar system are
represented here.
This entire exhibit is about size, and not much else. But the
absence of Pluto (even though the exhibit clearly states that
it's
the Jovian and Terrestrial planets that are represented) has led
about ten percent of our visitors to wonder where it is.
In the interest of sound pedagogy we have decided to explore two
paths: 1) Possibly add a sign at the right spot on the size
scales
exhibit that simply asks "Where's Pluto" and gives some
attention to
why it was not included among the models. And 2) We are further
considering a more in-depth treatment of the life and times of
Pluto
to add to our kiosks, which contain our computer-searchable data
base
of current astrophysics news that we display in a timely fashion
on a
video "bulletin" wall. This material might even contain
a sampling
of the various points-of-view expressed on how planets should be
counted for those who feel compelled to do so.
I close with the opinion that a mid-ex style mission to Pluto
might
resonate much more deeply with the public and with congress if
instead of saying "we must complete the reconnaissance of
solar
system's planets by sending probes to Pluto" we say "we
must BEGIN
the reconnaissance of a newly discovered, and hitherto uncharted
swath of real-estate in our solar system called the Kuiper belt,
of
which, Pluto reigns as king.
Respectfully Submitted
Neil deGrasse Tyson
Department of Astrophysics
& Director, Hayden Planetarium
Division of Physical Sciences
American Museum of Natural History
tyson@astro.amnh.org
http://research.amnh.org/astrophysics/tyson