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
--Richard L.S. Taylor, Probability Research Group, 1
"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 <email@example.com>
(3) THE FUTURE OF LIMITLESS ENERGY SUPPLIES: JAPAN PLANS ORBITING SOLAR
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 <firstname.lastname@example.org >
(7) ESTIMATING TOTAL MASS OF COMET POPULATION STILL A MAJOR PROBLEM
Lubos Neslusan <email@example.com>
(8) IS OUR SOLAR SYSTEM NOMENCLATURE IN CRISIS?
Phil Plait <firstname.lastname@example.org>
(9) PLUTO AND CHARON: BINARY PLANETS?
Michael Paine <email@example.com>
(1) METEORITE NARROWLY MISSES EARTH
From DPA (German Press Agency), 25 January 2001
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
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 <firstname.lastname@example.org>, 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
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
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
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
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
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
From SpaceDaily, 1 February 2001
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
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
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
"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
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
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
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
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 <email@example.com >
ASTEROIDS 2001: From Piazzi to the 3rd Millennium
Santa Flavia, Palermo, 11-16 June 2001
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.
Topics to be discussed at the conference include:
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,
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
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 <firstname.lastname@example.org>
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.
(8) IS OUR SOLAR SYSTEM NOMENCLATURE IN CRISIS?
From Phil Plait <email@example.com>
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 firstname.lastname@example.org
The Bad Astronomy Web Page: http://www.badastronomy.com
(9) PLUTO AND CHARON: BINARY PLANETS?
From Michael Paine <email@example.com>
As I indicated in my essay of 25 Sep 2000
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.
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OPEN LETTER TO READERS OF CCNet
From Neil de Grasse Tyson <email@example.com>
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 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
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
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.
Neil deGrasse Tyson
Department of Astrophysics
& Director, Hayden Planetarium
Division of Physical Sciences
American Museum of Natural History
CCCMENU CCC for 2000
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