PLEASE NOTE:


*

Date sent: Thu, 19 Mar 1998 14:21:18 -0500 (EST)
From: Benny J Peiser B.J.PEISER@livjm.ac.uk
Subject: CC DIGEST 19/03/98
To: cambridge-conference@livjm.ac.uk
Priority: NORMAL

CC DIGEST, 19 March 1998
------------------------

(1) WHAT ELSE LURKS OUT THERE?
Clark Whelton cwhelton@mindspring.com

(2) THERE ARE TWO ALAN W HARRIS'S, AFTER ALL
Alan W Harris (Berlin!) Alan.Harris@dlr.de

(3) PHYSICAL PROPERTIES OF COSMIC DUST
A.C. Levasseur Regourd et al., UNIVERSITY OF PARIS

(4) LONELY QUANDRANTIDS STILL SEARCHING FOR PARENTS
I.P Williams & S.J. Collander Brown, University of London

(5) ASTEROIDS OF THE FIRST-ORDER JOVIAN RESONANCE
D. Nesvorny & S. FerrazMello, UNIVERSITY OF SAO PAULO

(6) DYNAMICAL BEHAVIOUR OF OBJECTS IN THE ASTEROID BELT
A. Brunini, ASTRONOMICAL OBSERVATORY LA PLATA

(7) TWO DISTINCT POPULATIONS OF KUIPER-BELT OBJECTS
S.C. Tegler & W. Romanishin, NORTHERN ARIZONA UNIVERSITY

====================================
(1) WHAT ELSE LURKS OUT THERE?

From: Clark Whelton cwhelton@mindspring.com

Excerpts from

"What Else Lurks Out There? New Census of the Heavens Aims to Find Out"

by James Glanz

The New York Times Science Section, Tuesday, March 17, 1998

Apache Point, New Mexico. Perched on a platform that extends like a
diving board from this wind-whipped ridge 9,200 feet above sea level,
between the foothills of the Sacramento Mountains and the close night
sky, the new Sloan Telescope hardly looks imposing.

By astronomical standards, its 100-inch-diameter primary mirror is
modest in size, and outside of its small roll-away storage garage, the
squat cubelike structure of the telescope seems almost lost standing
naked in the night air.

But next month when it is joined to a new camera that now sits,
carefully tended, in a "clean room" nearby, the little Sloan will instantly
become powerful enough to plunge into the largest and most comprehensive
census of the visible universe that has ever been undertaken.

The project here in rugged mountain terrain 80 miles northeast of El
Paso, Texas, is called the Sloan Digital Sky Survey. At its heart will sit
a dark array of 54 silicon chips, known as "charge-coupled devices," or
C.C.D.'s, that will convert light from huge swaths of the New Mexico night
sky into digitalized images that can be poured onto magnetic tapes and into
computers for study. Built by Dr. James Gunn of Princeton University and
his collaborators, the C.C.D. camera will be hoisted into its place behind
the Sloan telescope this spring when it makes its first test observation, a
moment astronomers call "first light."

Once the problems have been worked out, over the next six years or
so, these C.C.D.'s should pour out a cornucopia of data: images in five
different colors of 50 million galaxies, 100,000 quasars, millions of
individual stars in this galaxy, and a whole menagerie of celestial
oddballs. The survey will be used for everything from finding the
sources of distant X-ray bursts to catching the glint of asteroids
whose orbits cross that of Earth.

"We are going to compile a field guide to the heavens," said Dr.
Michael Turner, an astronomer at the University of Chicago and the Fermi
National Accelerator Laboratory who is the spokesman for the $80 million
project. It involves researchers at Princeton, the U. of Chicago,
Fermilab, the Johns Hopkins University, the Institute for Advanced
Study, the United States Naval Observatory, the U. Of Washington and a
collaboration called the Japan Participation Group...

...The Survey will blanket a quarter of northern sky -- where
astronomers can most easily peer into deep space, away from the disk of this
crowded, dusty galaxy -- and probe selected slices in the south...

But the Sloan survey will not stop there. The consortium of
cosmologists plans to use the data from Sloan to produce a three-dimensional
scale model of a large chunk of the universe.

As images rush out of the C.C.D.camera at the rate of six trillion
bytes of data a year, supercomputers at Fermilab will sift the million
brightest out of the "field guide" and the Sloan telescope will more closely
examine the light from them using spectographs... This will let team
members measure precise distances to those galaxies, leading to the creation
of an exquisitely detailed three-dimensional map of Earth's corner of the
universe....

"We're looking into outer space to see back into inner space: the
first moments of the universe and the inner space of the elementary
particle," Dr. Turner said...

Not since the National Geographic Society-Palomar Observatory Survey
of the 1950s has a comprehensive census been attempted...

In a single image, the Sloan telescope can drink in a piece of the
sky the size of the Big Dipper's bucket -- an area much wider than a typical
astronomical telescope can observe in a single frame...

The objects will be sorted by their shapes, colors, locations,
brightnesses, approximate distances and other qualities... Said Bruce Margon
of the University of Washington, the scientific director of the survey,
"There is something in this for everyone." (c) The New York Times 1998

==========================
(2) EXAM QUESTION FOR OUR PROBABILITY BOFFINS:
"Among the world's population of 6 billion people, there are 150
professional NEO researchers. What are the chances that two of them
have exactly the same first, middle and surname, are part of the same
research team and are co-authors of a research paper?

From: Alan.Harris@dlr.de

Dear Benny,

Please note that the author list of the paper "The Near-Earth Objects
follow-up program - II. Results for 8 asteroids from 1982 to 1995, ICARUS,
1997, Vol.130, No.2, pp.275-286" should read:

P. Pravec*), M. Wolf, L. Sarounova, S. Mottola, A. Erikson, G. Hahn,
A.W. Harris, A.W. Harris, J.W. Young

In your CC DIGEST, 12/03/98 only one Harris appeared in the author list. It is
quite understandable that the duplication of the name in the author list is
assumed to be a misprint and deleted. The perverse fact is, however, that there
are two of us - one at JPL, Pasadena, the other at the DLR in Berlin - with
identical names (Alan William Harris), working in the same field. And we both
contributed to that paper.

Confusion is inevitable. We're working hard to prevent being merged into one
by the rest of the community!

Regards,

Alan Harris (DLR, Berlin)

==========================================
(3) PHYSICAL PROPERTIES OF COSMIC DUST

A.C. Levasseur Regourd*), M. Cabane, J.C. Worms & V. Haudebourg:
Physical properties of dust in the solar system: Relevance of a
computational approach and of measurements under microgravity
conditions, ADVANCES IN SPACE RESEARCH, 1997, Vol.20, No.8, pp.1585-1594

*) UNIVERSITY OF PARIS 06, AERON CNRS, BP 3, F-91371 VERRIERES
BUISSON, FRANCE

Dust agglomerates/particles in the solar system (e.g. regoliths,
cometary comae, interplanetary dust) are irregular aggregates whose
scattering properties (phase functions of the intensity and
polarization of scattered light) are drastically different from those
of Mie spheres. However, the observation of the light they scatter may
provide information on their physical properties. If the mechanism
which makes up the aggregates is invariant with time, they are likely
to be fractal particles, i.e. clusters formed of individual monomers.
Computations have been made using a Discrete Dipole Approximation with
hundreds of monomers; comparison with the observations suggests that
regoliths or dust clouds have a fractal dimension of the order of 2 and
consist of fluffy particles formed by Ballistic Cluster-Cluster
aggregation. To built the reference database required for deriving the
physical properties of these fluffy dust aggregates, and to avoid any
modification of the particles properties by levitation techniques, it
has been suggested to measure the scattering properties of numerous
samples under microgravity conditions. Results obtained during
parabolic flights show some discrepancy at large phase angles between
the results obtained under Earth's gravity and microgravity conditions,
the latter, being more reminiscent of solar system observations. (C)
1997 COSPAR. Published by Elsevier Science Ltd.

==========================
(4) LONELY QUANDRANTIDS STILL SEARCHING FOR PARENTS

I.P Williams & S.J. Collander Brown: The parent of the Quadrantid
meteoroid stream, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,
1998, Vol.294, No.1, pp.127-138

UNIVERSITY OF LONDON QUEEN MARY & WESTFIELD COLLEGE, ASTRONOMY
UNIT, MILE END RD, LONDON E1 4NS, ENGLAND I.P.Williams@qmw.ac.uk

The Quadrantid meteor shower is one of the major showers that produces
reliable displays every January. However, it is unique amongst the
major showers in still not having its parent uniquely identified. One
of the reasons for this may be because the stream, and presumably the
parent, lies in a region of the Solar system where near-resonant motion
with Jupiter, coupled with potential close encounters, is possible.
Such a combination can lead to a rapid dynamical evolution of an
orbit. In particular, it may be possible that the orbit of the parent
both satisfies the condition for a close encounter and is in resonant
motion, while most of the meteoroids cannot satisfy both conditions.
This results in the parent evolving away from the bulk of the stream.
To date, two suggestions have been made regarding possible parents for
the Quadrantid stream, these being Comet 1491 I and Comet 96P/Machholz,
The argument in favour of the first named being the parent is because
of the general similarity between the orbits around 1491. The argument
for comet 96P/Machholz being the parent is based on the similarity in
orbital evolution coupled with a similarity in orbits phase-shifted by
2000 yr. In this paper we suggest that on both counts asteroid 5496
(1973 NA) is more similar to the Quadrantids, and that even if 5496 is
not the actual parent in the strict sense that meteoroids are currently
being ejected, it is either likely to be a fragment of the parent or
the dormant remains of the parent. Copyright 1998, Institute for
Scientific Information Inc.

==============================
(5) ASTEROIDS OF THE FIRST-ORDER JOVIAN RESONANCE

D. Nesvorny & S. FerrazMello: On the asteroidal population of the
first-order Jovian resonances, ICARUS, 1997, Vol.130, No.2, pp.247-258

UNIVERSITY OF SAO PAULO, INSTITUE OF ASTRONOMY & GEOPHYSICS, AV MIGUEL
STEFANO 4200, BR-04301 SAO PAULO,BRAZIL

The frequency map analysis was applied to the fairly realistic models
of the 2/1, 3/2, and 4/3 jovian resonances and the results were
compared with the asteroidal distribution at these commensurabilities.
The presence of the Hecuba gap at the 2/1 and of the Hilda group in the
3/2 is explained on the basis of different rates of the chaotic
transport (diffusion) in these resonances. The diffusion in the most
stable 2/1-resonant region is almost two orders in magnitude faster
than the diffusion in the region which accommodates the Hildas. In the
2/1 commensurability there are two possible locations for
long-surviving asteroids: the one centered at an eccentricity of 0.3
near the libration stable centers with small libration amplitude and
the other at a slightly lower eccentricity with a moderate libration
amplitude (similar to 90 degrees). Surprisingly, all asteroids observed
in the 2/1 resonance (8 numbered and multi-opposition objects in
Bowell's catalog from 1994) occupy the moderate-libration area and
avoid the area in a close vicinity of the libration stable centers.
Possible explanations of this fact were discussed. Concerning the 4/3
resonance, the only asteroid in the corresponding stable region is 279
Thule, in spite of the fact that this region is almost as regular
(although not as extensive) as the one where the Hilda group in the
3/2, with 79 members, is found. (C) 1997 Academic Press.

===============================
(6) DYNAMICAL BEHAVIOUR OF OBJECTS IN THE ASTEROID BELT

A. Brunini: Dynamical behaviour of the primitive asteroid belt
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1998,
Vol.293, No.4, pp.405-410

ASTRONOMICAL OBSERVATORY, PROFOEG PASEO BOSQUE, RA-1900 LA PLATA,
ARGENTINA

In this paper we consider the dynamical evolution and orbital stability
of objects in the asteroid belt. A simple physical model, including
full gravitational perturbations from both giant planets, is used to
compute the dynamical evolution of 1000 test particles simulating the
primitive asteroids. The criterion of planet crossing (or close
approach in the case of resonant objects) is used to reject particles
from the simulation. 44 per cent of the particles survived for the
whole time-span covered by the numerical integration (similar to
10(9) yr). The 4:1, 3:1 and to a lesser extent the 2:1 Kirkwood gaps
are formed in similar to 10(7) yr of evolution, representing direct
numerical evidence about their gravitational origin. We found that the
rms eccentricity and inclination of the sample experience a fast
increase during the first 10(6) yr. The final rms eccentricity is 0.11,
similar to 60 per cent smaller than the present rms eccentricity
(0.17). Nevertheless, the gravitational action of the giant planets
suffices to prevent the formation of large objects, allowing
catastrophic collisions and the subsequent depletion of material from
this zone of the Solar system. The excited eccentricity by Jupiter
and Saturn may favour mutual encounters and the further
increase of the relative velocities up to their present values.
Copyright 1998, Institute for Scientific Information Inc.

==============================
(7) TWO DISTINCT POPULATIONS OF KUIPER-BELT OBJECTS

S.C. Tegler*) & W. Romanishin: Two distinct populations of Kuiper-belt
objects, NATURE, 1998, Vol.392, No.6671, pp.49-51

*)NO ARIZONA UNIVERSITY, DEPARTMENT OF PHYSICS & ASTRONOMY,
FLAGSTAFF, AZ, 86011, USA

The discovery of the first member of the Kuiper belt(1)-a formerly
hypothetical ancient reservoir of objects located beyond Neptune's
orbit-started a revolution in our understanding of the outer Solar
System: there is no longer a sharp edge at Pluto's orbit. About 60
Kuiper-belt objects, intermediate in size between comets and planets,
are now known(2) to exist on stable circular orbits around the Sun, and
no doubt many more objects await discovery. But owing to the recent
discovery and intrinsic faintness of these objects, little has been
done to explore their physical and chemical properties. Here we
report the results of a two-year survey of the broad-band optical
colours of about one-quarter of the known Kuiper-belt objects. We find
that their colours indicate the presence of two distinct populations:
one consists of objects whose surface colours are only slightly redder
than the colour of the Sun, while the other consists of the reddest
objects known in the Solar System. Copyright 1998, Institute for
Scientific Information Inc.

--------------------------------
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