Distant EKOs Issue #6, July 1999


News & Announcements
Abstracts of 5 Accepted Papers
Titles of 2 Submitted Papers
Abstracts of 3 Conference Contributions
Table of Contents of 1 Book
Newsletter Information


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


Water Ice on Kuiper Belt Object 1996 TO66
Robert H. Brown1, Dale P. Cruikshank2, & Yvonne Pendleton3
1 Lunar and Planetary Laboratory and Steward Observatory, University of Arizona, Tucson, AZ 85721
2 Mail Stop N245-6, NASA/Ames Research Center, Moffett Field, CA 94035
3 Mail Stop N245-3, NASA/Ames Research Center, Moffett Field, CA 94035

The 1.40-2.45 $\mu$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 $\mu$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

Evolution of Orbits at the 2:3 Resonance with Neptune
S.I. Ipatov1 and J. Henrard2
1 Institute of Applied Mathematics, Miusskaya sq. 4, Moscow 125047, Russia
2 Deptartement de Mathematique, Facultes Universitaires Notre-Dame de la Paris, Rempart de la Vierge 8, B-5000, Namur, Belgium

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 $\Delta \Omega = \Omega - \Omega_N$ in the longitudes of the ascending node of the body and Neptune and the argument of perihelion $\omega$. If $\Delta \Omega$ decreases and $\omega$ increases during evolution, then most of bodies leaves the resonance in 20 Myr. In the case of an increase of $\Delta \Omega$ and a decrease of $\omega$, bodies stay in the resonance for much longer time. Regions of eccentricities and inclinations, for which some bodies were in the $\eta_{18}$ secular resonance ( $\Delta \Omega
\approx$ const) and the Kozai resonance ( $\omega \approx$ 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 to The Earth
Sergei I. Ipatov1
1 Institute of Applied Mathematics, Miusskaya sq. 4, Moscow 125047, Russia

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 $d\ge 1$ 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

Keck Pencil-beam Survey For Faint Kuiper Belt Objects
E. I. Chiang1 and M. E. Brown1
1 California Institute of Technology

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 $m_V \leq
27.9$. Two new KBOs are discovered. One object having mV = 25.5 lies at a probable heliocentric distance $R \approx 33$ AU. The second object at mV = 27.2 is located at $R \approx 44$ 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, $\Sigma (<
m_R)$, is fitted to a power law of the form $\log_{10} \Sigma = \alpha (m_R -
23.5)$, where the slope $\alpha = 0.52 \pm 0.02$. 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; $d\!N \propto s^{-q} \, ds$, where the differential size index $q
= 3.6 \pm 0.1$. 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 $0.2 M_{\oplus}$ and $1 \times 10^{10}$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

Accretion in the Early Outer Solar System
Scott J. Kenyon1 and Jane X. Luu2
1 Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 USA
2 Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands

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 $m_R \ge$ 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:

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

Below are the abstracts of three articles regarding the Kuiper Belt.

Physical Nature of The Kuiper Belt
David Jewitt1 and Jane Luu2
1 Institute for Astronomy, University of Hawaii
2 Sterrewacht, Leiden University

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 ( $10 M_{\oplus}$?) 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 ($ \sim 10^3$ kg s-1), and the optical depth small ( $ \sim 10^{-7}$), 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

Dynamics of The Kuiper Belt
R. Malhotra1, M. Duncan2, and H. Levison3
1 Lunar and Planetary Institute
2 Queen's University
3 Southwest Research Institute

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

Formation and Collisional Evolution of
The Edgeworth-Kuiper Belt
Paolo Farinella1, Donald R. Davis2, and S. Alan Stern3
1 Department of Astronomy, University of Trieste, Italy
2 Planetary Science Institute, Tucson, USA
3 Southwest Research Institute, Boulder, USA

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.

Migration of Celestial Bodies in the Solar System

S.I. Ipatov


§ 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

§ 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

§ 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 $N_\pi$ 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 $N_\pi$
§ 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 $N_\pi$
§ 11. Interrelations of the variations in i, $\omega$, $\Omega$, 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

§ 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

§ 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 $\theta$ 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

§ 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

§ 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

§ 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


§ 1. The restricted circular problem of three bodies
§ 2. Various gravitational spheres
§ 3. Orbital elements
§ 4. Positions, velocities, and motion equations of bodies


§ 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


Newsletter Information

The Distant EKOs Newsletter is dedicated to provide researchers with easy and rapid access to current work regarding the Kuiper belt (observational and theoretical studies), directly related objects (e.g., Pluto, Centaurs), and other areas of study when explicitly applied to the Kuiper belt.

We accept submissions for the following sections:

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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.

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Joel Parker