PLEASE NOTE:
*
CCNet DIGEST, 10 March 1999
---------------------------
(1) A THREATENING PRESENCE FROM PLANET REMAINS
THE IRISH TIMES, 8 March 1999
http://www.irish-times.com:80/irish-times/paper/1999/0308/hom30.html
(2) HILTON BACK SPACE HOTEL: 'WE ONLY NEED $6 - $12 BILLION'
BBC News Online
http://news.bbc.co.uk/hi/english/sci/tech/newsid_293000/293366.stm
(3) SNL & JPL PROPOSE $1BILLION INTERSTELLAR EXPLORER
Scripps Howard News Service
http://www.bergen.com:80/morenews/spacetug199903098.htm
=====================
(1) A THREATENING PRESENCE FROM PLANET REMAINS
From THE IRISH TIMES, 8 March 1999
http://www.irish-times.com:80/irish-times/paper/1999/0308/hom30.html
From Larry Klaes <lklaes@bbn.com>
Massive building blocks left over after the planets formed still
orbit
the sun beyond Neptune, and every 100,000 years or so one wanders
towards us, posing an enormous risk to the Earth. Dick Ahlstrom
reports
on efforts to learn more about them.
Astronomers at Queen's University Belfast and Armagh
Observatory are undertaking an international study of a belt of
planetary leftovers, enormous objects up to 800km across
which orbit the sun beyond Neptune.
New "Trans-Neptunian Objects", TNOs, were being
discovered every month,
said Dr Alan Fitzsimmons, reader in observational astrophysics at
Queen's, although the first was identified only in September
1992.
The most recent, the 113th, was announced on February 16th, he
said,
and his group had discovered eight. He said the objects were
found in
what is known as the Kuiper Belt, a band of material in orbit
between
30 and 50 astronomical units (AU) from the sun.
An AU is equivalent to the distance of the Earth from the sun,
about 93
million miles.
The first astronomer to theorise about their presence was an
Irishman
from Streete, Co Westmeath, Kenneth Edgeworth, an accomplished
amateur
who published two papers in the 1940s.
These remained virtually unknown but the idea persisted,
culminating in
a paper in 1951 by a Dutch astronomer, Gerard Kuiper, whose name
now
describes their place in the solar system.
TNOs are remarkably difficult to spot, Dr Fitzsimmons explained,
because of their small size relative to their distance from us
and
because they don't reflect much light.
"These objects are darker than coal," he said,
"and you might expect to
find no more than one in an area of sky about the size of a full
moon."
This accounted for the long delay before the first TNO was
identified
seven years ago. It requires a very sensitive camera, but also
their
discovery was very much a matter of "believing that they
were there",
he said.
It is only in recent years that this has become possible, using a
combination of wide field CCD (charge-coupled device) cameras and
large
2.5-metre telescopes. The current generation of CCD cameras can
take
images of remarkably faint objects.
"We can see objects that are 15 million times fainter than
the faintest
star you could see on a dark night in Connemara," he said.
Observers use a trick of the ancient Greeks to distinguish the
planets
from the stars. It involves taking two images a given period of
time
apart and looking for near objects that have moved relative to
the
background of more distant stars. Knowing the time delay and the
distance travelled gives astronomers estimates of how far away
the
object is.
TNOs are of great interest to researchers. They are assumed to be
material left behind after the proto-planetary disc of matter
that must
have originally surrounded our sun condensed into planets.
"What we believe we are looking at are the remnant building
blocks of
the planets. Samples would tell us much about the stuff from
which
planets are made."
Researchers are also interested because the Kuiper Belt is
believed to
be the source from which short period comets arise. These include
Comet
Temple Tuttle, dust from which produces the annual November
Leonid
meteor showers.
Visitors from the Kuiper Belt could eventually become Earth
impactors.
TNOs drop out of the belt and move into the solar system proper
once
every 100,000 years or so and there are eight or nine known
objects
moving between Neptune and Jupiter, he said. "We believe
these are
slowly moving into the inner solar system."
The impactor thought to have wiped out the dinosaurs 65 million
years
ago was estimated to have been between one and two kilometres
across
(sic), but TNOs range from 50km up to 800km, with most falling
between
100km and 400km.
It is thought that any TNO making it past Jupiter's gravitational
pull
would be broken up into smaller pieces, but these would still
represent
a serious threat if they drifted towards us.
There is a move afoot to have the Kuiper Belt renamed the
Edgeworth-Kuiper Belt and to rechristen TNOs as Edgeworth-Kuiper
Objects, said Dr Mark Bailey, director of the Armagh Observatory.
While it does seem that Kuiper did not rely on Edgeworth's work,
his
earlier papers are documented and they do predate Kuiper.
It shows that Ireland's size does not militate against its
position in
international research.
Copyright 1999, The Irish Times
==================
(2) HILTON BACK SPACE HOTEL
From BBC News Online
http://news.bbc.co.uk/hi/english/sci/tech/newsid_293000/293366.stm
By BBC News Online Science Editor Dr David Whitehouse
The hotel group Hilton International is to become the first
sponsor of
a privately funded plan to build a space station. It will be
constructed from used Space Shuttle fuel tanks.
And when the Hilton Orbital Hotel is built, space visionary
Arthur C
Clark wants to be there for the opening.
The project, called Space Islands, will connect together Space
Shuttle
fuel tanks, each the diameter of a Boeing 747 aircraft. At
present they
are the only part of Nasa's Space Shuttle that is not reused.
British Airways are also said to want to become involved in the
project. Under consideration is a survey of BA and Hilton
customers
asking them if they would like to take a holiday in space.
They would be asked if they wanted it to be entirely gravity free
and
if they would like large windows to view the Earth. Would they
like to
take a spacewalk is another possible question.
"There is powerful support for this concept in
Washington," said Space
Island Group director Gene Meyers.
He told BBC News Online "There is no technical reason why it
cannot be
done."
He hopes that the project will excite major companies to sponsor
the
project in the same way that they sponsor the Olympics.
"We need $6 - $12 billion," he said, "That is a
fraction of the [$40bn]
cost of the space station that is currently being built by the
USA,
Russia and other countries."
The space station would be made out of empty space shuttle fuel
tanks.
Currently, they are used once and allowed to fall back to Earth,
burning up in its atmosphere. However they could easily be kept
in
space and outfitted as living quarters.
The most optimistic schedule for its construction is six years,
given
the money and the will to do it.
"Eventually there could be several of these space stations
in orbit,"
says Meyers, "It would even be possible to put one in a
figure-of-eight
orbit around the Earth and the Moon. That would be quite a
vacation."
The idea of using spent Space Shuttle fuel tanks is not new. It
was
once considered by Nasa as the basis for its own space station.
However
it was discarded as being too simple. It was possibly also seen
as too
commercial for an organisation that sees its role mainly in
research
and development.
Up to 100 people at a time could be ferried up to the orbital
hotel, if
a second-generation space shuttle was built.
Space visionary Arthur C Clarke has been an enthusiastic backer
of the
project for a year.
He was to approach film director Stanley Kubrick to become
involved.
Together they designed the famous wheel-shaped space station for
the
film "2001 - A Space Odyssey."
But Kubrick's recent death has ended the chance for him to see
his
vision turned into reality.
It is no coincidence that in "2001 - A Space Odyssey"
part of the space
station is a Hilton hotel. The hotel group paid to be part of the
film.
Thirty years later Arthur C Clark has once again approached the
company
to be part of the new initiative.
"This space station could be built, there is no reason why
it can't"
said Gene Meyers "all we need is for people to find out that
it can be
done and then help us do it."
Copyright 1999, BBC
=====================
(3) SNL & JPL PROPOSE $1BILLION INTERSTELLAR EXPLORER
From Scripps Howard News Service
http://www.bergen.com:80/morenews/spacetug199903098.htm
Tuesday, March 9, 1999
By LAWRENCE SPOHN
ALBUQUERQUE, N.M. -- The ultimate road trip, a nearly 100
billion-mile
excursion out of the solar system, is being proposed by
scientists at
government laboratories in New Mexico and California.
Their proposed interstellar space cruiser would haul a 1-ton
telescope
into the unexplored frontier of interstellar space at 380,000
mph, give
or take a few thousand mph.
Collaborating scientists at the Department of Energy's Sandia
National
Laboratories in Albuquerque and NASA's Jet Propulsion Laboratory,
in
Pasadena, Calif., say that not only is mankind's first
interstellar
mission "doable" next decade, but its potential
achievements also make
it extremely worthy.
FULL STORY:
http://www.bergen.com:80/morenews/spacetug199903098.htm
Copyright 1999, Scripps Howard News Service
----------------------------------------
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*
LETTERS TO THE MODERATOR, 10 March 1999
---------------------------------------
(1) ON THE YARKOVSKY EFFECT
Paolo Farinella <paolof@keplero.dm.unipi.it>
(2) MORE ON THE YARKOVSKY EFFECT
William Bottke <bottke@astrosun.tn.cornell.edu>
(3) A CHIP OFF THE MOON?
Rolf Sinclair <rsinclai@nsf.gov>
(4) IS SPACEGUARD TOO CHEAP?
Richard A Kowalski <bitnik@bitnik.com>
(5) NEMESIS: BILL NAPIER'S SCIENCE FICTION THRILLER
Michael Paine <mpaine@tpgi.com.au>
=====================
(1) ON THE YARKOVSKY EFFECT
From Paolo Farinella <paolof@keplero.dm.unipi.it>
Dear Benny,
Enzo Zappala's comment in the March 9th CCNet Letters reveals
that, as
it was probably the case for other people, he has read the
(oversimplified) press reports on our Yarkovsky work, but not the
original paper published in SCIENCE (March 5th, 1999) or the
preprint
available on my website for several weeks before publication
[http://tycho.dm.unipi.it/~paolof].
Our work shows that for multi-km asteroids the Yarkovsky effect
can
shift the semimajor axis by 0.01-0.02 AU - not much, but enough
to
inject them in one of the many, thin resonances criss-crossing
the
inner asteroid belt, as discussed by Migliorini et al. (1998, the
same
SCIENCE paper that Enzo mentions) and Morbidelli & Nesvorny
(ICARUS,
submitted). The Yarkovsky drift, according to our estimates,
increases
by a factor 3-4 the flux into the resonances of small main-belt
asteroids, and thus, indirectly, the flux feeding the
Mars-crossing and
eventually the Earth-crossing populations. In summary: the
Migliorini
et al. and our mechanism work in synergy, not as alternatives!
Paolo Farinella
================
(2) MORE ON THE YARKOVSKY EFFECT
From William Bottke <bottke@astrosun.tn.cornell.edu>
Dear Benny,
I would like to comment on Vincenzo Zappala's recent message that
the
Yarkovsky effect may not be needed to deliver main belt fragments
to the
Earth-crossing region.
Vincenzo correctly points out that the combination of mean motion
resonances with Mars, three body mean motion resonances with
Jupiter-Saturn, and Mars close encounters are now the favored
delivery
scenario to bring multi-km asteroids to the NEO region
(Migliorini et
al. 1999, Science, 281, 2022). He also correctly points out that
the
Yarkovsky effect, a thermal drag force, is too weak to move large
objects very far (~0.01 AU for R = 1-10 km bodies over their
lifetimes).
The point of the Farinella and Vokrouhlicky Science paper is,
however,
that the Yarkovsky effect helps resupply the narrow Mars and
Jupiter-Saturn resonances with main belt material.
Collisions probably
cannot do it alone; the total width of the 100 or so tiny
resonances
between 2.15 AU and 2.45 AU is ~ 0.03 AU, such that ejecta only
has
about a 10% chance of ending up in a resonance after being
launched
from its parent body. Estimates show that there are not
enough
moderate-eccentricity multi-km bodies in the main belt to keep
the
Mars-crossing asteroids in steady state via these resonances, nor
are
their enough multi-km fragments produced by collisions to keep
these
resonances filled with fresh material.
Thus, a plausible alternative is that the Yarkovsky effect and
the
Migliorini et al. resonances work in concert to provide material
to the
inner solar system: (i) A multi-km asteroid is created in a
collision,
(ii) it is slowly dragged into a resonance via the Yarkovsky
effect,
(iii) the asteroid has its eccentricity pumped up to reach a
Mars-crossing orbit, and (iv) Mars close encounters remove the
object
from resonance and eventually move onto an Earth-crossing orbit.
Best regards,
Bill Bottke
Cornell University
=====================
(3) A CHIP OFF THE MOON?
From Rolf Sinclair <rsinclai@nsf.gov>
Re: A Chip off the Moon? <Simon Mansfield>
There was a telescopic search at the Earth's L4 and L5 points in
the
'70's by the Lunar & Planetary Lab, U. Arizona. When I
mentioned this
at a talk I gave at Northern Arizona Univ. in 1987, a staff
member from
the Lowell Observatory pointed out that they had done such a
search a
decade or so earlier. (I believe the late Clyde Tombaugh was
involved
in this search.) Sorry I don't have the exact references at hand.
The
LPL work was published in ICARUS; I don't know where the Lowell
work
was published. These labs should be able to give more details.
Rolf Sinclair
P.S. Neither study found anything "natural or
artificial" (as the LPL
paper put it).
=====================
(4) IS SPACEGUARD TOO CHEAP?
From Richard A Kowalski <bitnik@bitnik.com>
Benny and Michael,
On the subject of Spaceguard not costing enough to be taken
seriously... I would have to agree and I'll give you a small,
somewhat
off topic, but albeit, telling episode.
In the FAQ for my mailing list (Minor Planet Mailing List) I have
a
statement that any person can do useful astrometry for under $500
US.
It is assumed that one has a computer, since it is posted on the
internet, but I also assumed a person interested enough could
grind a
mirror and build a CCD camera for small money today. The
reduction
software is available for free. Donated optics and/or CCDs can
even be
found on occasion to lower the costs further.
I was surprised by the number of responses which I got
(from a few
well known amateurs at that) who said I was being disingenuous by
quoting such a small amount.
I stand behind this number (for the above cited reasons) and can
see
the amount even dropping further in the not too distant future...
I would not be surprised that governments and other institutions
feel
$10 Million per year isn't enough to consider funding Spaceguard
too.
"Save the world for only $10 million per year? Ha!"
This might also suggest that we are looking for funding in the
wrong
places.
In the past several years, the insurance industry has been taking
the
subject of Global Warming seriously because they would be
directly
affected by having to pay out claims.
In recent years, attention has been drawn to massive flooding not
only in the US
but around the world. There has also been a surge of building
along sea
coasts and recent hurricanes have emptied the coffers of these
companies because of damage claims. El Nino is just one other
"Global"
event which the insurance companies are affected by.
Granted, asteroids which are "Global Killers" (1 km or
larger) would in
effect absolve these companies from having to pay out, because
there
wouldn't be anyone to write the check, or to accept it or even a
place
to cash it! "Regional Killers", "State
Killers" or "City Killers" would
be taken more seriously by these companies because even if one of
these
bodies impacted in an ocean, they would have to pay out
incredible sums
for property damage (flooding) and human death and injury claims.
Possibly those involved in trying to obtain funding for
Spaceguard
through individual governments should instead turn their
attentions to
insurance companies instead. Their "bean counters" take
disasters into
account every day... Government "beanies" don't...
Just my $0.02
--
Richard Kowalski
Quail Hollow
Observatory Minor
Planet Mailing List
http://www.bitnik.com/QHO
http://www.bitnik.com/mp
761 Zephyrhills
"One thing I learned at home, on those nights at home, I
learned how to
use a telescope and how to find objects in the sky. You don't do
that
by going to a bar and drinking beer"
Clyde Tombaugh - Discoverer of Pluto
==========================
(5) NEMESIS: BILL NAPIER'S SCIENCE FICTION THRILLER
From Michael Paine <mpaine@tpgi.com.au>
Dear Benny,
I have just finished reading NEMESIS, the new science fiction
thriller
by astronomer Bill Napier. Arthur C Clarke is quoted on the
cover: "The
most exciting book I have ever read" (see also CCNet Digest
4/11/98). I
agree with Sir Arthur!
Not that I am complaining but ... it took me months to gather
information about the NEO hazard for the Australian Spaceguard
Survey
web pages. Most of this information is now succinctly covered by
Bill
Napier in briefings and other conversations between scientists,
military personnel and politicians - so you can learn all about
the NEO
hazard while enjoying a thrilling story.
The paperback version is now on sale in Australia - Big W has it
on
special for AU$16 (tip off from Rob McNaught)
Michael Paine
-----------------
CCNet-LETTERS is the discussion forum of the Cambridge-Conference
Network. Contributions to the on-going debate about near-Earth
objects,
the cosmic environment of our planet and how to deal with it are
welcome. To subscribe or unsubscribe from CCNet-LETTERS, please
contact
Benny J Peiser at <b.j.peiser@livjm.ac.uk>.
The fully indexed archive
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http://abob.libs.uga.edu/bobk/cccmenu.html
*
A CLARIFICATION
From Vincenzo Zapalla <zappala@otoax4.to.astro.it>
Dear Benny,
I completely agree with the comments of Paolo and Bill. However,
the
purpose of my letter was different. In fact, the contribution of
Yarkovsy
effect to the general problem of the origin of NEA is probably
well
understood by myself and all the other colleagues involved in
this field.
However, information like that furnished in the article from The
New York
Times of March 9 (reported by Henry Fountain) can be highly
misleading.
Some readers can understand that Yarkosvky effect alone has
solved the
mistery of the origin of NEA. The problem is much more complex.
The
aim of my letter was just to address this fact and to put the
topic under
a correct light. In this respect, I thank very much Paolo and
Bill in having
helped me in doing so.
V. Zappala