Well, in some form of historical revisionism, the number of objects found in 1998 continues to climb, and in mid-May temporarily surpassed the number of objects found so far in 1999. Similarly, ``new'' objects from as far back as 1995 are being reported.
The scattered disk is finally making a stronger appearance. New discoveries and revised orbital elements for some objects discovered earlier this year now puts the list of assumed SDOs at five:
| Object | a | e | i |
| 1996 TL66 | 85 | 0.59 | 24 |
| 1999 CF119 | 115 | 0.69 | 20 |
| 1999 CV118 | 57 | 0.39 | 6 |
| 1999 CY118 | 95 | 0.64 | 26 |
| 1999 DG8 | 82 | 0.60 | 40 |
Note in particular the impressive semi-major axis for 1999 CF119, the new record-holder. Also, 1998 DG8 was discovered at a heliocentric distance of 61 AU; as quoted in M.P.E.C. 1999-M30, ``it is clear that 1999 DG8 was being observed at a distance that is substantially greater than that at which any other solar-system object has been observed.''
A feature characteristic of water ice has been detected in a spectrum of 1996 TO66. The abstract for that ApJ article is in this issue.
Request for Collaboration: Joel Parker has a number of observing runs in the following semester for recoveries of EKOs and Centaurs. Dates are: August 5-6, September 16-17, November 29-30, and December 27-30. If you are interested in coordinating with him for followup observations of newly discovered objects or contemporaneous observations (e.g., lightcurves or visible-IR colors), please contact him at: joel@boulder.swri.edu or by phone at 303-546-0265.
There were 38 new EKO discoveries announced since the previous issue of the Distant EKOs Newsletter:
1995 SM55, 1995 TL8, 1996 GQ21, 1996 TC68, 1998 HJ151, 1998 HK151, 1998 HL151, 1998 HM151, 1998 HN151, 1998 HO151, 1998 HP151, 1998 HQ151, 1998 HR151, 1998 SM165, 1999 DB8, 1999 DC8, 1999 HA12, 1999 HB12, 1999 HC12, 1999 HR11, 1999 HS11, 1999 HT11, 1999 HU11, 1999 HV11, 1999 HW11, 1999 HX11, 1999 HY11, 1999 HZ11, 1999 DD8, 1999 DE8, 1999 DF8, 1999 DG8, 1999 JA132, 1999 JB132, 1999 JC132, 1999 JD132, 1999 JE132, 1999 JF132
and 5 new Centaur discoveries:
1995 SN55, 1998 BU48, 1998 TF35, 1999 HD12, 1999 JV127
Current number of EKOs: 174 (and Pluto & Charon)
Current number of Centaurs: 14
The 1.40-2.45 
m spectrum of Kuiper Belt object 1996 TO66 was measured at the Keck Observatory in 1998 September. Its spectrum
shows the strong absorptions near 1.5 and 2.0 m that are
characteristic of water ice--the first such detection on a Kuiper Belt
object. The depth of the absorption bands and the continuum reflectance
of 1996 TO66 suggest the presence of a black- to slightly
blue-colored, spectrally featureless particulate material as a minority
component mixed with the water ice. In addition, there is evidence that
the intensity of the water bands in the spectrum of 1996 TO66varies with rotational phase, suggesting a "patchy" surface.
Published in: The Astrophysical Journal, 519, L101
For preprints, contact rhb@abante.lpl.arizona.edu
Results of numerical investigations of the evolution of orbits at the 2:3
resonance with Neptune are presented. The gravitational influence of four giant
planets was taken into account. For identical initial values of semimajor
axes, eccentricities and inclinations but for different initial orbital
orientations and initial positions in orbits, we obtained various types of
variations in the difference
in the
longitudes of the ascending node of the body and Neptune and the argument of
perihelion 
.
If
decreases and
increases during
evolution, then most of bodies leaves the resonance in 20 Myr. In the case of
an increase of
and a decrease of ,
bodies stay in the
resonance for much longer time. Regions of eccentricities and inclinations, for
which some bodies were in the 
secular resonance (
const) and the Kozai resonance (
const) were obtained
to be larger than those predicted for small variations in the critical angle.
Some bodies can be at the same time in both these resonances.
To appear in: Solar System Research, No. 4, 1999
For preprints, contact ipatov@spp.keldysh.ru
Migration of trans-Neptunian objects under their mutual gravitation influence
and the influence of the giant planets is investigated. These investigations
are based on computer simulation results and on some formulas. We estimated
that about 20% of near-Earth objects with diameter 
km may have come
from the Edgeworth-Kuiper belt.
To appear in: Celest. Mech. & Dyn. Astronomy, in press
For preprints, contact ipatov@spp.keldysh.ru
We present the results of a pencil-beam survey of the Kuiper Belt using the
Keck 10-m telescope. A single 0.01 square degree field is imaged 29 times for a
total integration time of 4.8 hr. Combining exposures in software allows the
detection of Kuiper Belt Objects (KBOs) having visual magnitude
.
Two new KBOs are discovered. One object having
mV = 25.5 lies at a
probable heliocentric distance
AU. The second object at
mV =
27.2 is located at
AU. Both KBOs have diameters of about 50 km,
assuming comet-like albedos of 4%.
Data from all surveys are pooled to construct the luminosity function from mR
= 20 to 27. The cumulative number of objects per square degree,
,
is fitted to a power law of the form
,
where the slope
.
Differences between slopes
reported in the literature are due mainly to which survey data are incorporated
in the fit, and not to the method of analysis. The luminosity function is
consistent with a power-law size distribution for objects having diameters s= 50-500 km;
,
where the differential size index
.
The distribution is such that the smallest objects possess most
of the surface area, but the largest bodies contain the bulk of the mass. We
estimate to order-of-magnitude that
and
comet progenitors lie between 30 and 50 AU. Though our inferred size index
nearly matches that derived by Dohnanyi (1969), it is unknown whether
catastrophic collisions are responsible for shaping the size distribution.
Impact strengths may increase strongly with size from 50 to 500 km, whereas the
derivation by Dohnanyi (1969) assumes impact strength to be independent of
size. In the present-day Belt, collisional lifetimes of KBOs having diameters
50-500 km exceed the age of the Solar System by at least 2 orders of
magnitude, assuming bodies consist of solid, cohesive rock. Implications of the
absence of detections of classical KBOs beyond 50 AU are discussed.
To appear in: Astronomical Journal, September 1999
For preprints, contact echiang@tapir.caltech.edu
or on the web at http://www.its.caltech.edu/~eugene/ppp/ppp.html
We describe calculations of the evolution of an ensemble of small
planetesimals in the outer solar system. In a solar nebula with a
mass of several times the Minimum Mass Solar Nebula, objects with
radii of 100-1000 km can form on timescales of 10-100 Myr. Model
luminosity functions derived from these calculations agree with
current observations of bodies beyond the orbit of Neptune (Kuiper
Belt objects). New surveys with current and planned instruments can
place better constraints on the mass and dynamics of the solar nebula
by measuring the luminosity function at red magnitudes 
28.
To appear in: Astrophysical Journal
E-mail contact: skenyon@cfa.harvard.edu
Preprints on the web at: http://xxx.lanl.gov/abs/astro-ph/9906143
Uranus and Neptune: Refugees from the Jupiter-Saturn Zone?
Edward W. Thommes1, Martin J. Duncan1, & Harold F. Levison2
1Department of Physics, Queen's University, Kingston, Ontario, Canada K7L 3N6
2Space Studies Department, Southwest Research Institute, Boulder, CO 80302
Submitted to: Nature
E-mail contact: thommes@astro.queensu.ca
Near-Infrared Spectroscopy of Centaurs and Irregular Satellites
Michael E. Brown1
1Division of Geological and Planetary Sciences, California Institute of Technology
Submitted to: The Astronomical Journal
Preprints on the web at: http://www.gps.caltech.edu/~mbrown/papers/pubs.html
On-line preprints of all the chapters in the Protostars and Planets IV conference proceedings book can now be downloaded from:
The book is divided into the following eight sections:
Below are the abstracts of three articles regarding the Kuiper Belt.
Recent ground-based observations have unveiled a large number of bodies in
orbit beyond Neptune, in a region now widely known as the Kuiper (or, less
commonly, Edgeworth-Kuiper) Belt. About 105 Kuiper Belt Objects (KBOs) with
diameters larger than 100 km exist in the 30 AU to 50 AU trans-Neptunian
region. Their combined mass is about 10% of that of Earth. The orbits of KBOs
fall into at least three distinct dynamical classes (the "Classical" objects,
the Plutinos and the "Scattered" objects). Each throws light on physical
processes operating in the solar system prior to and during the formation of
the planets. The Kuiper Belt is significant both as the likely source of the
short-period comets (and the dynamically intermediate Centaurs), and as a
repository of the solar system's most primitive (least thermally processed)
material. KBOs show an unexpected and presently unexplained diversity of
surface colors, possibly reflecting intrinsic compositional variations and
transient resurfacing by impacts. The present-day Kuiper Belt is probably the
surviving remnant of a once much more massive (
?) preplanetary
disk. It is very likely that collisions and disk-planet interactions played a
major role in shaping this early precursor. While the collisional production
of dust is presently modest (
kg s-1), and the optical depth
small (
), the early Belt was probably very dusty and may have
sustained a disk analogous to those reported around some nearby main-sequence
stars.
To appear in: Protostars and Planets IV, University of Arizona Press
Preprints available on the web at http://www.ifa.hawaii.edu/faculty/jewitt/papers/PPIV
Our current knowledge of the dynamical structure of the Kuiper Belt is reviewed here. Numerical results on long term orbital evolution and dynamical mechanisms underlying the transport of objects out of the Kuiper Belt are discussed. Scenarios about the origin of the highly non-uniform orbital distribution of Kuiper Belt objects are described, as well as the constraints these provide on the formation and long term dynamical evolution of the outer Solar system. Possible mechanisms include an early history of orbital migration of the outer planets, a mass loss phase in the outer Solar system and scattering by large planetesimals. The origin and dynamics of the scattered component of the Kuiper Belt is discussed. Inferences about the primordial mass distribution in the trans-Neptune region are reviewed. Outstanding questions about Kuiper Belt dynamics are listed.
To appear in: Protostars and Planets IV, University of Arizona Press
For preprints, contact renu@lpi.jsc.nasa.gov
or on the web at http://xxx.lanl.gov/ps/astro-ph/9901155
We provide a summary of current research concerning the formation and the collisional history of the Edgeworth-Kuiper belt. Collisions appear to have first built up sizable (up to Pluto-sized) bodies in a primordial, massive planetesimal population. Then, following the formation of Neptune, collisional grinding has been eroding the population at diameters smaller than about 100 km, at a variable extent depending on heliocentric distance. In both phases collisional evolution has interacted in a complex way with a variety of subtle dynamical processes, and this interplay has been responsible for stopping accretion and for ejecting bodies (including the currently observed Jupiter-family comets) from the stable regions of orbital element space. We compare the properties and history of the transneptunian belt to those of main-belt and Trojan asteroids, and discuss the recent evidence for similar disks of planetesimals and debris around both newly-formed and main-sequence stars.
To appear in: Protostars and Planets IV, University of Arizona Press
Preprints available on the web at http://astro.caltech.edu/~vgm/ppiv/preprints.html
This is a contents of a book which is in press in Russian. The publication of the book was in the plan for 1998, but as the Russian Foundation for Basic Research had no money in 1998 for publications, it moved to 1999. Now the Publishing company URSS has received money from the Foundation and began preparing the book. So, probably, the book will be published in 1999.
INTRODUCTION
Chapter I. THE STRUCTURE OF THE SOLAR SYSTEM
§ 1. Planets, their satellites and rings
§ 2. The main asteroid belt
§ 3. Proper orbital elements and asteroid families
§ 4. Resonances in the asteroid belt
§ 5. Trojans
§ 6. Near-Earth objects
§ 7. Collisions of celestial bodies with the Earth, craters
§ 8. Meteorites
§ 9. Giant-planet crossers. Centaurs
§ 10. Trans-Neptunian objects
§ 11. Oort and Hills clouds
§ 12. Comets
§ 13. Meteor streams
§ 14. Planet accumulation
Chapter II. EVOLUTION OF TWO CLOSE HELIOCENTRIC ORBITS OF GRAVITATIONALLY
INTERACTING BODIES
§ 1. Variants of calculations of the evolution of two celestial objects
§ 2. Calculations with integration to various precisions on a step
§ 3. Types of variations in orbital elements
§ 4. Ranges of initial data in which the variations in orbital elements are
of the various types
§ 5. Comparison with results of other authors
§ 6. Motion around triangular libration points
§ 7. Maximum eccentricities and distances from the Sun for two gravitationally
interacting bodies
§ 8. The case of initially eccentric orbits
§ 9. Transitions of bodies in resonant orbits
Chapter III. EVOLUTION OF ASTEROIDAL ORBITS AT THE 5:2 RESONANCE
§ 1. Variants of calculations of the orbital evolution of two objects
§ 2. Formulas for conversion from rectangular to orbital coordinates free of
singularities at zero inclinations and eccentricities
§ 3. Maximum values of eccentricities of fictitious asteroids
§ 4. Formation of the 5:2 Kirkwood gap
§ 5. Asteroids reaching the orbit of the Earth
§ 6. Properties of the distribution of asteroids near the 5:2 gap
§ 7. Types 
of interrelations of the variations in the eccentricity and
longitude of perihelion when the periods of these variations are the
same
§ 8. Transitions between different types
§ 9. Interrelations of the variations in the orbital elements when the periods
of the long-period variations in the eccentricity and longitude of
perihelion differ
§ 10. Regions of initial data corresponding to different types
§ 11. Interrelations of the variations in i, , 
, and e
§ 12. Variations of the orbital elements over the period Te of the
long-period variations in the eccentricity
§ 13. Peculiarities of the variations in the orbital elements at large
inclinations
§ 14. Limits and periods of variations in the orbital elements
§ 15. Dependence of the variations in the orbital elements on the initial data
Chapter IV. SIMULATION OF ORBITAL EVOLUTION OF CELESTIAL BODIES BY THE SPHERES'
METHOD
§ 1. Algorithm of the spheres' method
§ 2. Characteristic time elapsed up to a collision or a close encounter of two
bodies up to the distance equal to the radius of the considered sphere
§ 3. Comparison of results obtained by the sphere's method and by numerical
integration of motion equations
§ 4. Relative motion of encounting bodies
§ 5. Main principles of construction of the computer simulation algorithm of
the evolution of disks consisting of a large number of planetesimals
§ 6. Number of encounters and collisions of bodies in the disk during some time
interval
§ 7. Characteristic variations in orbital elements at one encounter up to the
radius of sphere of action
Chapter V. LIMITING MODELS OF THE EVOLUTION OF A DISK OF BODIES MOVING AROUND
THE SUN
§ 1. Results of simulation of the evolution of disks initially consisting of
hundreds of bodies
§ 2. Evolution of a disk consisting of a large number of bodies
§ 2.1. Variations in average eccentricity
§ 2.2. Variations of the Safronov's parameter 
during plane
accumulation
§ 2.3. Evolution time of a disk consisting of almost the same bodies
§ 2.4. Evolution times of disks consisting of various bodies
§ 3. Characteristic times elapsed up to collisions of small bodies with a
larger body
§ 4. Formation of planets' spins
§ 4.1. Review of the results obtained by other authors
§ 4.2. Spin momenta of accumulating bodies
§ 4.3. Formation of axial rotations of planets in the case of accumulation of
solid bodies
§ 4.4. Formation of axial rotations of planets in the case of coagulations of
rarefied condensations
Chapter VI. MIGRATION OF BODIES IN THE ACCUMULATION OF PLANETS
§ 1. Migration of bodies in formation of the terrestrial planets
§ 2. Migration of bodies in formation of the giant planets
§ 3. Influence of migrating bodies on the evolution of the asteroid belt
§ 4. Migration of planetesimals in the zone of the giant planets after the
formation of the main mass of these planets
Chapter VII. MIGRATION OF SMALL BODIES TO THE EARTH
§ 1. Characteristic times elapsed up to collisions and close encounters of
bodies in a disk
§ 2. Migration of bodies from the asteroid belt to the Earth's orbit
§ 3. Migration of trans-Neptunian objects due to their gravitational influence
§ 3.1. Calculations of orbital evolution of several gravitationally interacting
objects
§ 3.2. Evolution of eccentricities of trans-Neptunian objects
§ 3.3. Evolution of semimajor axes of trans-Neptunian objects
§ 3.4. Probabilities of collisions of trans-Neptunian objects
§ 4. Migration of trans-Neptunian objects under the influence of the giant
planets
§ 5. Evolution of orbits for the 2:3 resonance with Neptune
§ 5.1. Types of evolution
§ 5.2. Variations in orbital elements
§ 6. Orbital evolution of the objects P/1996 R2 and P/1996 N2
§ 7. Investigations of migration of small bodies under the influence of planets
with the use of the spheres' method
§ 7.1. Variants of the computer runs
§ 7.2. The ejection of bodies into hyperbolic orbits and their collisions with
planets
§ 7.3. Migration of bodies in the Solar System
§ 7.4. Times of evolution of the disks of bodies
§ 8. Characteristic times elapsed up to the collisions of bodies with the Earth
§ 8.1. Characteristic times elapsed up to the collisions of near-Earth objects
with the Earth
§ 8.2. The migration of bodies and meteorite ages
§ 8.3. The collision frequency of bodies having various masses with the Earth
§ 8.4. Times elapsed up to collisions of bodies with various planets
§ 8.5. Portion of trans-Neptunian bodies reaching the Earth's orbit
Appendix 1. METHODS OF A CHOICE OF PAIRS OF ENCOUNTING BODIES
§ 1. Probabilistic choice of pairs of contacting objects
§ 2. The general scheme of the method of conditional triangular matrix
§ 3. Equivalency of the method of a conditional triangular matrix to the method
of ``full search''
§ 4. Periodical renumbering of objects
§ 5. Comparison of the efficiency of different methods
§ 6. Algorithm modifications providing an additional increase of the
calculations' velocity
Appendix 2. VARIATIONS IN ORBITAL ELEMENTS OF PLANETS
Appendix 3. SOME CELESTIAL MECHANICS' FORMULAS
§ 1. The restricted circular problem of three bodies
§ 2. Various gravitational spheres
§ 3. Orbital elements
§ 4. Positions, velocities, and motion equations of bodies
Appendix 4. RECEIVING ASTRONOMICAL DATA BY INTERNET
Appendix 5. DYNAMICAL ASTRONOMY IN THE WORLD
§ 1. Foreign dynamical astronomy
§ 1.1. Astronomical organizations
§ 1.2. Grants
§ 1.3. Contacts
§ 2. Impressions from scientific visits
§ 3. Science in the USSR and in Russia
§ 4. Wishes to future scientists
§ 5. Specialists in dynamical astronomy
§ 6. Addition made in 1999
Appendix 6. AUTOBIOGRAPHICAL MEMOIRS
We accept submissions for the following sections:
Distant EKOs is not a refereed publication, but is a tool for furthering communication among people interested in Kuiper belt research. Publication or listing of an article in the Newsletter or the web page does not constitute an endorsement of the article's results or imply validity of its contents. When referencing an article, please reference the original source; Distant EKOs is not a substitute for peer-reviewed journals.