PLEASE NOTE:
*
CCNet SPECIAL, 20 May 1999
NEO RESEARCH & IMPACT RISK DEBATES BETWEEN OPENESS AND
RESTRAINT
----------------------------------------------------------------
POEM OF THE DAY - FROM CCNet's
SPACE-POET LAUREATE
Deadly rocks
Copernicus, Kepler and maybe Newton, too
felt that there must be harmony and
order in the universe.
Each planet in its orbit, majestically
tracing out
God's directive, or like the huge and
polished flywheel
of some monster steel and brass machine
moving in exact, unerring circles for
ever and a day.
Little did they know of past encounters,
the late heavy bombardment of left over
pieces
that marked the face of every solid
globe,
and later still, the devastation from
the sky
that fried a billion trilobites, or left
huge saurians
starving in the dark, with scars still
on the Earth
that only time and rain and plate
tectonics healed.
At last we know that tiny planetoids
abound,
and while they mostly huddle in bounded
bands
under the pull of larger worlds, a few
will always stray
and of those some will target Earth,
where our
own numbers make us vulnerable
to deadly rocks and chunks of iron out
of space.
20.5.99
Malcolm Miller
<stellar2@actonline.com.au>
(1) WHAT ARE THE LESSONS FROM 1997 XF11 and 1999 AN10?
Brian Marsden <marsden@cfa0.harvard.edu>
(2) MOTION OF THE DANGEROUS ASTEROID 1997 XF11
G. Sitarski, UNIVERSITY OF BIALYSTOK
(3) YES, MINISTER: I THINK THIS ASTEROID REQUIRES A RHODESIA
SOLUTION
Robert Clements <Robert.Clements@dva.gov.au>
(4) DON'T WITHHOLD SCIENCE DATA FROM THE PUBLIC
Jim Benson <Jim@SpaceDev.Com>
(5) WHAT WOULD AN10 LOOK LIKE IF IT WERE TO COME CLOSE TO EARTH?
Arvind Paranjpye <arp@iucaa.ernet.in>
(6) WE'RE AFRAID THE CCNet MIGHT BE VERY DANGEROUS
Vincenzo Zappala' <zappala@otoax4.to.astro.it>
(7) CCNet ONLY REFLECTS ACTUAL SCIENTIFIC PROBLEMS & DEBATES
Benny J Peiser <b.j.peiser@livjm.ac.uk>
(8) IMPACT EARTH
Austin Atkinson <ultrazone@easynet.co.uk>
(9) PREPRINTS FOR PROTOSTARS AND PLANETS IV
Sara Russell <sarr@nhm.ac.uk>
(10) CLOSE SHAVE WITH ASTEROID
BBC Online Network, 19 May 1999
(11) YOU'VE GOT TO LAND - TO UNDERSTAND (MATHILDE)
Erik Asphaug <asphaug@es.ucsc.edu>
=================
(1) WHAT ARE THE LESSONS FROM 1997 XF11 and 1999 AN10?
From Brian Marsden <marsden@cfa0.harvard.edu>
Dear Benny,
I suppose one can legitimately debate
whether it was appropriate
for you to draw attention originally to the 1999 AN10 paper by
Milani
et al. (and whether it was appropriate for them to place their
paper
matter-of-factly in the internet), but I do not understand how
Clark
Chapman can object to your now following up the story. Having
whetted
appetites, you owed it to your readers to bring them up-to-date
with
the latest developments. After all, the CCNet is not a newspaper
that
casually reports stories, but a medium for discussing NEO issues
and
providing relevant additional information. Many readers were
surely
expecting that further observations of 1999 AN10 would be made
during
the upcoming weeks and months, but given the earlier large
uncertainty
in the predicted 2027 miss distance, I suppose we were all a bit
surprised the actual miss distance then should be as small as it
is.
But that's the way it goes sometimes: it's the luck of the draw.
It's also why it is important to carry out continuing
observations of NEOs
and to make the related computations. I, for one, would have
thought
the post-conjunction observations would immediately allow us to
dismiss
any possibility whatsoever of the 2039 impact! But, no, as
Paul Chodas
stated (and was in my mind when I prepared MPEC 1999-K07, even if
I did
not say so), the earlier impact probability has been increased by
a
factor of somewhere between 20 and 100. Sure, 1 in a 10 million
is
still 100 times less than the annual chance of impact by an
unknown
1-km object, but is the 2039 impact probability going to increase
by a
further factor of 100 as additional observations of 1999 AN10
come
along? Probably it won't, but nobody can yet say that for sure.
What we specifically need to establish is what
1999 AN10's
revolution period, currently 1.76 years, will be after the
perturbations by the earth have modified it in 2027. If the
period
changes to 1.75 years, there will be another close approach in
2034,
and that is a necessary prerequisite for the 2039 impact. The
nominal
orbit given on MPEC 1999-K07 yields a post-2027 revolution period
of
1.86 years. If this turns out to be anywhere near correct, 1999
AN10
can come nowhere near the earth in 2034. Actually, 1.86 years is
close
to the largest the period can be for this object after
2027. On the
other hand, the period might turn out to be as short as 1.68
years. If
the period is 1.85714... years, then we can expect a close
approach
seven revolutions of 1999 AN10 and thirteen revolutions of the
earth
later, i.e., in 2040. This case was in fact already
considered by
Milani et al., and they found that no earth impact would be
possible in
that year.
The similarity to the 1997 XF11 situation
continues to be quite
startling. Nobody knew it at the time (or for many months
thereafter),
but when that object was first announced on 1997 Dec. 23 there
was
a 1-in-10-million chance it would hit the earth on 2040 Oct. 26.
When
attention was (rather dramatically) drawn to that object on 1998
Mar.
11, the improved definition of the 2028 approach increased that
2040
impact probability, again by a factor of about 100, up to 1 in
100,000,
which is about ten times the annual impact probability of an
unknown
object of its presumed size, 2 km. Of course, the next day, in
response
to the publicity, we had the measurements of the images from the
1990
films, and the probability of 2040 impact dropped immediately to
zero.
As Clark Chapman says, "PHA cases like AN10 are
now routinely having
their future 'near misses' calculated", and that is indeed
as it should
be. Of the "lessons learned last year from XF11", that
is the only one
that is of significance. If that came from my stirring things up
on
1998 Mar. 11, that is surely good. Actually, as CCNet readers
know, it
did not in fact come immediately. I had to stir things up further
in
June and July, by specifically pointing out a possible grazing
impact
in 2037 and a possible deep impact in 2040. And the big issue of
1998
was of course "peer review". Well, almost 10 months
after I mentioned
the 2040 impact, Paul Chodas recently presented a paper on the
subject
at a meeting in Colorado. He completely confirmed my estimate (in
the
CCNet this past January) that the 2040 impact probability for
1997 XF11
had attained a maximum of about 1 (actually 2) in 100,000.
Ten months to complete a peer review--and one that
confirmed the
original calculation! Well, I suppose it is good that we have
sped that
process up, first with the work he, Karri Muinonen and I did on
the
Milani 1999 AN10 paper, then with our repetition of the new 1999
AN10
computations during the past couple of days. But did we expect
the
various computations to be significantly different? Of course, we
didn't--and they weren't! These were computations that anybody
who
knows about orbits can do--and did. Chapman continues to state
that "an
astronomer erroneously predicted that 1997 XF11 had a 1-in-1000
impact
probability in 2028". His implication is that I was that
astronomer. I
was not. That 1-in-1000 probability was publicized by another
astronomer who did not understand the figures given on IAU
Circular No.
6837. If "peer review" is needed, it is with regard to
wild statements
such as Chapman himself makes--like the very curious one in the
Nov.-Dec. 1998 "Planetary Report" apparently denying
any need for NEO
observations beyond the first few days after discovery.
Well, the
cases of both 1997 XF11 and 1999 AN10 surely show otherwise...
But I do agree with Chapman that, as we
discover more and
intrinsically fainter PHAs, we shall find many cases of impact
probabilities verging on significance. Those of us in the PHA
business
obviously need to monitor these, principally by obtaining further
observations when appropriate. And there clearly won't need to be
a
news story, and perhaps not even a mention in CCNet, every
time. But
the "cottage industry" that developed concerning 1997
XF11 and 1999
AN10 is still in its infancy, and astronomers not directly
involved in
the computations have been slow to embrace it. Nevertheless,
particularly now with the IMPACT meeting coming up in Turin
during the
first week in June, I hope that the turning point has been
reached.
Regards
Brian G. Marsden
=================
(2) MOTION OF THE DANGEROUS ASTEROID 1997 XF11
G. Sitarski: Motion of the dangerous asteroid 1997 XF11. ACTA
ASTRONOMICA, 1999, Vol.49, No.1, pp.103-112
UNIVERSITY OF BIALYSTOK,INST PHYS,LIPOWA 41,PL-15424
BIALYSTOK,POLAND
Minor planet 1997 XF11, discovered in December 1997, is moving in
the
heliocentric orbit which almost intersects the Earth orbit. In
October
2028 the asteroid will approach the Earth to within 0.006 a.u. We
improved the asteroid's orbit on the base of 151 astrometric
observations from 1990-1998. To investigate the long-term motion
of the
asteroid we randomly selected 500 sets of orbital elements and
numerically integrated the equations of motion by the recurrent
power
series. We followed evolution of minimum distances between orbits
of
1997 XF11 and the Earth for moments of consecutive passages of
the
asteroid through its descending node. We found that only in 2042
the
minimum distance between orbits of both planets could be smaller
than
the Earth radius. However, the asteroid will pass through its
descending node in July 2042 while a collision with the Earth
could
happen during the October encounter. After 2042 the minimum
distance
between orbits of both planets will be permanently growing up,
and
hence we estimate that during the next several thousand years
collision
with the Earth will be impossible. We also investigated the
asteroid's
motion before 1990. We found that past close approaches of 1997
XF11 to
the Earth occurred in 1971 to within 0.032 a.u, and in 1957 to
within
0.015 a.u. We calculated ephemerides of the asteroid for those
past
approaches aiming at finding some old observations of the minor
planet.
We have also studied accuracy of prediction of the future motion
of
1997 XF11 based, however, on 142 observations of the asteroid
from
1997/98 only. We found that in that case possibility of collision
during 2030-2050, although possible, is completely unpredictable.
Copyright 1999, Institute for Scientific Information Inc.
=================
(3) YES, MINISTER: I THINK THIS ASTEROID REQUIRES A RHODESIA
SOLUTION
From Robert Clements <Robert.Clements@dva.gov.au>
At the risk of Sir Humphrey Appleby, I wonder if we need a
Rhodesia
Solution here.
(I assume that you would be familiar within the British comedy
series,
"Yes, Minister"; but if you aren't: the "Rhodesia
Solution" is called
upon in an episode (The Whisky Priest) where Hacker has to pass
sensitive information to the PM that everyone (inc. Hacker) wants
suppressed. The RS is to phrase the message precisely but
bureaucratically; so the information is present but it's
importance is
carefully hidden).
It's hard not to sympathise with both sides of the argument: CC
is
completely correct in saying that the more alerts we have, the
less
alert people will be when a serious crisis arises; while you're
equally
correct in saying that additional observations of these things
need to
be encouraged while any observations can actually be made. Is it
possible to develop a simple advice protocol that gets the
"please
look" message out to the people who can do the looking
without
introducing the word impactor into the equation (assuming that we
are
talking @ least a medium-term uncertainty... the APD seems to me
fairly
justified if we're talking shorter term situations). Sure it's
euphemistic, sure it's bureaucratic; but in this age of instant
information, euphemism & bureaucracy are starting to look
surprisingly
like survival techniques....
(I'm curious, though: has the orbit of 1999 AN10 been nailed to
the
extent that the numbers for a robotic rendezvous probe could
currently
be crunched? Even without overdramatising the situation, the 600
years
of certainty seems to suggest that this is one celestial
neighbour we
need to get to know...)
All the best,
Robert Clements <Robert.Clements@dva.gov.au>
<http://www.ausnet.net.au/~clemensr/welcome.htm>
=================
(4) DON'T WITHHOLD SCIENCE DATA FROM THE PUBLIC
From Jim Benson <Jim@SpaceDev.Com>
Benny,
I am appalled that anyone in the scientific community would ever
want
to withhold any science data from the public, for any reason! It
just
boggles my mind. Who and what do they think they are protecting?
Is
there some kind of scientific arrogance or job protection scheme
going on
below the surface?
Thank you for your objective and persistent efforts in this area.
Please keep up the good work.
Jim Benson
SpaceDev - NEAP (Near Earth Asteroid Prospector)
-o- Commercial Space Exploration & Development of Space
Resources -o-
http://www.spacedev.com
-o- Info@SpaceDev.Com
To the Moon, asteroids and
Mars, and beyond to the stars.
===================
(5) WHAT WOULD AN10 LOOK LIKE IF IT WERE TO COME CLOSE TO EARTH?
From Arvind Paranjpye <arp@iucaa.ernet.in>
Dear Benny,
this is about 1999 AN 10 -- you wrote that the "object might
come as
close as 37,000 km on August 7, 2027"
Does it mean that we will miss it by a margin of just about
21 minutes or so?
Has any one calculated its magnitude as it zooms pass the earth?
Regards
Arvind
===============
Moderator's note: The following communication has been posted at
the
special request of Vincenzo Zappala', Alberto Cellino and Patrick
Michel
(6) WE'RE AFRAID THE CCNet MIGHT BE VERY DANGEROUS
From Vincenzo Zappala' <zappala@otoax4.to.astro.it>
Dear Benny,
after the overabundance of discussions, polemics, confusions,
etc.
appeared in CCNet during last weeks, we intend to propose an open
debate during the plenary session of the forthcoming IMPACT
workshop
(Torino, June 1-4) on "the role of CCNet in NEO search and
dissemination". We think this is required since we have
found a strong
and possibly dangerous modification of the original goals.
Indeed, we are afraid that the way CCNet works now can be very
dangerous and lead to a very misleading interpretation of the
scientific results by the media.
Vincenzo Zappala', Alberto Cellino, Patrick Michel
===============
(7) CCNet ONLY REFLECTS ACTUAL SCIENTIFIC PROBLEMS & DEBATES
From Benny J Peiser <b.j.peiser@livjm.ac.uk>
Dear Vincenzo, Alberto and Patrick
I would be more than happy to participate in a debate about
"the role
of the CCNet" which you intend to propose for the plenary
session of
the forthcoming IMPACT workshop. I am sure that a number of other
colleagues are equally concerned about the way the CCNet is
sometimes
posting controversial issues related to NEO research (although I
doubt
whether many would agree that CCNet is "very
dangerous").
I believe that much of what is posted on the CCNet is simply a
natural
reflection of *actual* problems we are currently facing within
NEO
and impact research. In additon, I would argue that it is very
healthy
for our openmindedness and scientific credibility that such
debates are
conducted wide in the open - particularly in view of the great
public
interest in the impact hazard and the uncertainties we are
dealing
with.
In case your proposal will be accepted by the organising
committe, I
would be more than happy to discuss the function of e-mail
networks in
the area of today's science in general and the role of the CCNet
in
particular.
Please let me know what kind of format you have in mind for such
a
debate and whether or not you would like me to introduce CCNet
and the
function I believe it has.
I look forward to meeting you in Turin.
With best wishes,
Benny
===================
(8) IMPACT EARTH
From Austin Atkinson <ultrazone@easynet.co.uk>
IMPACT EARTH BY AUSTEN ATKINSON,
PUBLISHED BY VIRGIN
MAY 20 1999 (UK)
PRICE £16.99
Benny,
it may interest fellow subscribers to know that my new book
IMPACT
EARTH, which focuses on the impact problem, is released in the
UK today. It will be published internationally in the near
future.
The book is written for the "common man", an attempt to
explain the
nature of the impact hazard and to encourage some understanding
and
acceptance of the impact phenomenon at grass roots level. I am a
full
time popular-science author and television producer and have
endeavoured to bring what is essentially a difficult (and often
pilloried) subject to the attention of all.
If my fellow list subscribers feel that members of their families
or
other "non-scientists" would like an insight into the
problem, Impact
Earth may be for them. I focus on the human issue, in an attempt
to
make the threat personal. It is after all quite difficult for
many
people on the street to see celestial objects and mother Earth as
being
in anyway connected. It is nigh on impossible for many,
therefore, to
connect small bodies in space with potential global devastation
on
Earth. So Impact Earth attempts to politicise the topic and give
expression to the views of many leading scientists in this field.
Furthermore Impact Earth gives voice to my concerns (concerns
clearly
shared by you Benny and many subscribers to CCNET) that there is
a
conspiracy of silence within the scientific community regarding
potential impacts and to a similar lack of open discussion in
political
circles.
The book includes interviews with scientists from organisations
as
diverse as Sandia National Laboratory, to John¹s Hopkins
University (in
particular their Shield initiative), through to the Natural
History
Museum in London. The book has a foreword by Brian Marsden (Minor
Planet Centre) and an afterword by Jay Tate of Spaceguard UK.
There are numerous bookshop events scheduled (more to be
confirmed in
the near future) in the UK and a list of these can be seen at the
following url:
http://easyweb.easynet.co.uk/~ultrazone/book_signing_promo1.html
I would be delighted to welcome list members at any of these
events and
hope that fellow subscribers and members of Spaceguard will make
themselves known to me during the course of the proceedings.
I will be using the fifty plus radio, TV and newspaper/magazine
interviews organised by my publicists at Virgin to further the
general
aim of increasing public awareness of this issue. I hope
that CCNET¹s
subscribers may find something of interest in Impact Earth.
Austen Atkinson
Hampshire, UK
ultrazone@easynet.co.uk
=============
(9) PREPRINTS FOR PROTOSTARS AND PLANETS IV
From Sara Russell <sarr@nhm.ac.uk>
Preprint versions of all the review chapters from the Protostars
and Planets
IV book have been pasted on our website, with the permission of
the
publishers, University of Arizona Press. Preprints can be
downloaded
from:
http://astro.caltech.edu/~vgm/ppiv/
Protostars and Planets IV comprises 49 reviews by 166
collaborating
authors. It is divided into eight sections:
Molecular Clouds and Star Formation
Circumstellar Envelopes and Disks
Young Binaries
Jets and Outflows
Early Solar System and Planet Formation
Comets and the Kuiper Belt
Extrasolar Planets and Brown Dwarfs
Initial Conditions for Astrobiology
Editors: V. Mannings, A. P. Boss, & S. S. Russell
*************************************
Dr Sara Russell,
Meteorite Researcher,
Department of Mineralogy,
The Natural History Museum,
Cromwell Road,
London,
SW7 5BD, U.K.
Tel: +44 (0) 171 938 8776
Fax: +44 (0) 171 938 9268
=============
(10) CLOSE SHAVE WITH ASTEROID
From the BBC Online Network, 19 May 1999
http://news.bbc.co.uk/hi/english/sci/tech/newsid_347000/347764.stm
By BBC News Online Science Editor Dr David Whitehouse
A large asteroid could miss the Earth by only 38,000 kilometres
in
2027, according to new astronomical observations. This is an
extremely
close shave - the Moon orbits ten times further from Earth.
The calculations suggest that an impact is not possible that year
but,
in theory, the Earth's gravity could perturb the asteroid's path,
possibly leading to an impact in 2039.
The near-miss trajectory of a newly-discovered asteroid, called
1999
AN10, was announced in April. Now, the observational data of
Australian
astronomer F. Zoltowski allows calculations of just how close the
asteroid may come to Earth.
Closer and closer
Astronomers at the Minor Planet Center at the US
Smithsonian
Astrophysical Observatory used Zoltowski's work to work out an
estimated approach distance for AN10 of 56,500 kilometres from
Earth.
The fly-by will occur on August 7, 2027.
But the closest possible distance that AN10 could come to the
Earth on
that day is only 38,000km.
The calculations suggest the asteroid will not impact. But the
new
calculations confirm the initial speculation that the asteroid
might
approach within the Earth's sphere of gravitational influence.
It could therefore be perturbed in such a way that it might
impact some
years later.
Impossible to predict
Dr Benny Peiser of Liverpool John Moores University in England
says
that the chaotic behaviour of this asteroid makes it practically
impossible to predict all possible approaches for more than a few
decades after any close encounter.
He says the orbit will remain dangerously close to the orbit of
the
Earth for about 600 years.
Astronomers stress that a collision is only one of a range of
possibilities for this kilometre-wide chunk of rock. If it did
strike,
it would cause continent-wide devastation and alter the Earth's
climate.
Copyright 1999, BBC
================
(11) YOU'VE GOT TO LAND - TO UNDERSTAND (MATHILDE)
From Erik Asphaug <asphaug@es.ucsc.edu>
Dear Benny,
In countering the trajectory of poet Malcolm Miller's notion that
NEAR
had performed a 'merciless interrogation' of asteroid Mathilde, I
probably applied too great a corrective thrust. Radar
reconnaisance
will soon fill in the shape of the hemisphere unimaged by NEAR's
flawless flyby, and we might enjoy some resolved looks at
Mathilde from
future telescopes. But it will be decades before we know more
about
this particular asteroid than its shape, its mass, its albedo and
some
of its color -- alongside NEAR's record of a strange geology,
about
which we know even less.
On a more positive note, it is delightful that the once-lowly
asteroid
('these clods of dirt...' -- K.F. Gauss) has risen to inspire
poetry. I
am reminded of a shorter poem whose authorship escapes me but
that
Johnny Cochran might have written: 'You've got to land / to
understand.'
Erik Asphaug
asphaug@earthsci.ucsc.edu
----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
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
*
CCNet SPECIAL
-------------
1999 AN10 GOES OVER THE TOP DOWN UNDER
From Sydney Morning Herald
[http://www.smh.com.au/news/9905/21/text/pageone2.html]
OUTBACK AMATEUR DISCOVERS ASTEROID THREAT TO THE WORLD
Friday, May 21, 1999
By JAMES WOODFORD, Science Writer
Over the next three decades the world will become obsessed with
1999 AN10 -- a kilometre-long asteroid which an Australian
amateur
astronomer has revealed as the most deadly known object in outer
space.
Searching the sky last week with his $7,200, 30-centimetre
diameter
telescope from his front yard at Woomera in South Australia, Mr
Frank
Zoltowski made six observations of AN10 just before sunrise over
two
days.
The asteroid, was almost due east of his home, 25 degrees above
the
horizon, 160 million kilometres away, and travelling at around 45
kilometres per second. As a result of his observations,
astronomers have
realised that AN10 will (sic) pass as close as 39,000 kilometres
from
Earth in 2027, instead of previous and much more comfortable
predictions
of 30 million kilometres (sic).
The Minor Planet Centre, based at the Smithsonian Astrophysical
Observatory in the United States, has posted it on its Internet
home
page as a new threat to the world (sic).
And resident astronomer at the Siding Spring Observatory and
member of
NASA's committee assessing the danger of near Earth objects, Mr
Ken
Russell, said the asteroid could cause damage on a continental
scale.
Mr Russell said it was "much more massive" than the
object which caused
a vast area of Siberian forest to be flattened in 1908, which was
only
50
to 60 metres in length.
"This is the first known object which is on a potential
collision course
with Earth which is large enough to cause a disaster on a global
scale,"
he said. "If AN10 hit it would lift enough dirt into the
atmosphere to
cause an impact winter."
Mr Zoltowski said it was "coal-coloured" but about a
million times more
faint than visible for the naked eye.
"Someday, somewhere, something is going to hit. It is just
the
environment of the solar system."
Even if it does pass Earth at the shockingly close distance -- in
space
terms -- of 39,000 kilometres, it will still place some
satellites at
risk and create one of history's most impressive light shows. The
object
will return in 2038 and will be even more of a threat (sic).
Mr Russell said humans have 40 years to learn about AN10.
"It's small
enough that we could probably divert it from impact if we wanted
to."
Copyright 1999 Sydney Morning Herald
==================
WHAT 1999 AN10 MIGHT LOOK LIKE
From Jonathan Shanklin <j.shanklin@bas.ac.uk>
A rough calculation suggests that 1999 AN10 will move northwards
from
the southern skies in early August 2027, brightening quite
rapidly. At
closest approach it will be moving at over 10 degrees per hour.
It will
peak at brighter 4th magnitude shortly after closest approach and
will
fade more slowly. It will only spend around 5 days brighter than
14th
mag.
Evidence so far clearly suggests that unless attention is drawn
to these
unusual objects, no specific attempt is made to observe them or
chase up
archive material. The controversial IAU circular(s) and CCNet are
clearly required to provoke professional observers into action
and to
encourage amateur observers to attempt difficult
observations. In some
cases the action appears to consist of attempts at denigrating
these
efforts. It would be interesting to know how many observations of
XF11
and AN10 these critics have made.
Jon Shanklin
j.shanklin@bas.ac.uk
http://www.nbs.ac.uk/public/icd/jds