Distant EKOs, Issue #25  (September 2002)


News & Announcements
Abstracts of 8 Accepted Papers
Title of 1 Submitted Paper
Titles of 3 Other Papers of Interest
Conference Contributions
Description and Contents of 1 Book
Newsletter Information


The National Research Council recently released the Solar System Exploration Decadal Survey ``New Frontiers in the Solar System: An Integrated Exploration Strategy''. The Survey reviews the current state of planetary science and exploration, and makes recommendations for investments in ground-based and space flight research for the next decade, 2003-2013. The Kuiper belt figures prominently throughout the report. Of particular interest to readers of this newsletter is the Survey's very strong support for a Kuiper Belt-Pluto Explorer mission, which is given the highest priority recommendation for its class (medium cost Solar System Flight Missions). The report also recommends support for ground-based telescope projects, such as the Large-aperture Synoptic Survey Telescope (LSST) and the Giant Segmented Mirror Telescope (GSMT), explicitly including Kuiper belt studies as a major science driver. The report can be ordered at http://www.nationalacademies.org/ssb/ and the full text of the report can be obtained in three PDF files at http://www.aas.org/~dps/decadal/

The ``Pluto Portal'' is now available at: http://www.boulder.swri.edu/plutoportal/

And yet more Pluto news: the Pluto occultation observing campaign was successful in making detections during the July 20 and August 21 events. Preliminary results show that Pluto's atmosphere is cooling and going though other global changes. See:

Followup HST observations by Noll et al. have confirmed that 1997 CQ29 is, indeed, a binary. Original images on the WF3 CCD, only showed possible elongation of the object; these new observations with the PC CCD clearly resolve the components, which have a separation of 0.33 arcsec and confirmed binary motion.
IAUC 7959: http://cfa-www.harvard.edu/iauc/07900/07959.html

Similarly, Keck observations by Romanishin et al. confirm the binarity of 2000 CF105:
IAUC 7962: http://cfa-www.harvard.edu/iauc/07900/07962.html

There were 3 new TNO discoveries announced since the last issue of the Distant EKOs Newsletter:

2002 AW197, 2002 KW14, 2002 KX14

and 3 new Centaur/SDO discoveries.

2002 KY14, 2002 JR146, 2002 PN34

Reclassified objects:
2002 GP32 (TNO $\rightarrow$ SDO)
1999 CG119 (TNO $\rightarrow$ SDO)

Objects recently assigned numbers:
1999 OX3 = (44594)
2000 PV29 = (45802)

Objects recently assigned names:
1999 HX11 = Rhadamanthus

Current number of TNOs: 563 (and Pluto & Charon, and 7 other TNO binary companions)
Current number of Centaurs/SDOs: 120


Observational Limits on a Distant Cold Kuiper Belt
R.L. Allen1, G.M. Bernstein1, and R. Malhotra2

1 Department of Astronomy, University of Michigan, 830 Dennison Bldg, Ann Arbor, MI 48109-1090, USA
2 Department of Planetary Sciences, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, USA

Almost all of the >500 known Kuiper belt objects (KBOs) have been discovered within 50 AU of the Sun. One possible explanation for the observed lack of KBOs beyond 50 AU is that the distant Kuiper belt is dynamically very cold, and thus thin enough on the sky to have slipped between previous deep survey fields. We have completed a survey designed to search for a dynamically cold distant Kuiper belt near the invariable plane of the Solar system. In $2.3~{\rm deg}^2$ we have discovered a total of 33 KBOs and 1 Centaur, but no objects in circular orbits beyond 50 AU. We find that we can exclude at 95% CL the existence of a distant disk inclined by $i \le 1^\circ$ to the invariable plane and containing more than 1.2 times as many D>185 km KBOs between 50 and 60 AU as the observed inner Kuiper belt, if the distant disk is thinner than $\sigma=1.75^\circ$.

To appear in: The Astronomical Journal

For preprints, contact rhiannon@astro.lsa.umich.edu

Planetary Perturbations on the
2:3 Mean Motion Resonance with Neptune
Tetsuharu Fuse1

1 Subaru Telescope, NAOJ, 650 North Aohoku Place, Hilo, HI 96720, USA

A mean motion resonance with Neptune is one of the major dynamical characteristics of the Edgeworth-Kuiper Belt Objects that spread over the outside of Neptune's orbit. We investigated the influence of Jupiter, Saturn, and Uranus on the dynamical structure of the 2:3 mean motion resonance with Neptune. Since the distance between the planets and objects has great influence on the dynamical structure, numerical integrations were carried out for test particles for 5 Myr under five fictitious solar-system models having different configurations. In discussion about the results, we concentrate on the size of the EKBO eccentricities, e, because they have an especially close relation to the orbital evolution; for example, larger e objects have more opportunities to encounter other objects or planets. By comparing the results of each model, it was found that the resonance structure is not largely affected by Jupiter and Saturn, and that the largest eof the resonant objects depends on the distance between Uranus and the resonance. The distance also influences the structure around the resonance because of variation in the secular resonance positions. We further found that the largest e values of the non-resonant objects at each semi-major axis do not depend on the distance from Uranus; however, they depend on the distance from Neptune.

Published in: Publications of the Astronomical Society of Japan, 54, 493 (2002 June)

For reprints, contact tetsu@subaru.naoj.org

On the Plutinos and Twotinos of the Kuiper Belt
E.I. Chiang1 and A.B. Jordan1

1 Center for Integrative Planetary Sciences, UC Berkeley Astronomy, Berkeley, CA 94720, USA

We illuminate dynamical properties of Kuiper Belt Objects (KBOs) in the 3:2 (``Plutino'') and 2:1 (``Twotino'') Neptunian resonances within the model of resonant capture and migration. We analyze a series of numerical integrations, each involving the 4 migratory giant planets and 400 test particles distributed throughout trans-Neptunian space, to measure the efficiencies of capture into the 3:2 and 2:1 resonances, the efficiencies of capture into Kozai-type secular resonances, and the libration centers and amplitudes of resonant particles, all as functions of the migration speed. We synthesize instantaneous snapshots of the spatial distribution of $\sim$104resonant KBOs, from which we derive the longitudinal variation of the sky density of each resonant family. Twotinos cluster $\pm 75^\circ$away from Neptune's longitude, while Plutinos cluster $\pm 90^\circ$away. Such longitudinal clustering persists even for surveys that are not volume-limited in their ability to detect resonant KBOs. Remarkably, between $-90^\circ$ and $-60^\circ$ of Neptune's longitude, we find the ratio of sky densities of Twotinos to Plutinos to be nearly unity despite the greater average distance of Twotinos, assuming the two resonant populations are equal in number and share the same size, albedo, and inclination distributions. We couple our findings to observations to crudely estimate that Plutinos intrinsically outnumber Twotinos by a factor not exceeding $\sim$3. Most strikingly, the migration model predicts an asymmetry in the spatial distribution of Twotinos: more Twotinos are expected to lie at longitudes behind that of Neptune than ahead of it. The magnitude of the asymmetry amplifies dramatically with faster rates of migration and can be as large as $\sim$300%. A differential measurement of the sky density of 2:1 resonant objects behind of and in front of Neptune's longitude would powerfully constrain the migration history of that planet.

To appear in: The Astronomical Journal

For preprints, contact echiang@astron.berkeley.edu
or on the web at http://astron.berkeley.edu/~echiang/ppp/ppp.html

A Study of the Dynamics of Dust from the Kuiper Belt:
Spatial Distribution and Spectral Energy Distribution
Amaya Moro-Martín1 and Renu Malhotra2

1 Steward Observatory, University of Arizona, 933 N. Cherry Av, Tucson, AZ 85721, USA
2 Department of Planetary Sciences, University of Arizona, 1629 E. University Boulevard, Tucson, AZ 85721, USA

The dust produced in the Kuiper Belt (KB) spreads throughout the Solar System forming a dust disk. We numerically model the orbital evolution of KB dust and estimate its equilibrium spatial distribution and its brightness and spectral energy distributions (SED), assuming greybody absorption and emission by the dust grains. We show that the planets modify the KB disk SED, so potentially we can infer the presence of planets in spatially unresolved debris disks by studying the shape of their SEDs. We point out that there are inherent uncertainties in the prediction of structure in the dust disk, owing to the chaotic dynamics of dust orbital evolution imposed by resonant gravitational perturbations of the planets.

To appear in: The Astronomical Journal

For preprints, contact amaya@as.arizona.edu
or on the web at http://www.lpl.arizona.edu/people/faculty/malhotra2.html

Long-term Evolution of Objects in the Kuiper Belt Zone -- Effects of Insolation and Radiogenic Heating
Young-Jun Choi1, Merav Cohen1, Rainer Merk1, and Dina Prialnik1

1 Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv 69978, Israel

The Kuiper Belt zone is unique insofar as the major heat sources of objects a few tens of kilometers in size -- solar radiation on the one hand, and radioactive decay on the other -- have comparable power. This leads to unique evolutionary patterns, with heat waves propagating inward from the irradiated surface and outwards from the radioactively heated interior. A major radioactive source that is considered in this study is 26Al. The long-term evolution of several models with characteristics typical of Kuiper Belt objects is followed by means of a 1-D numerical code that solves the heat and mass balance equations on a spherically symmetric grid. The free parameters considered are radius (10-500 km), heliocentric distance (30-120 AU), and initial 26Al content (0- $5\times10^{-8}$ by mass). The initial composition assumed is a porous mixture of ices (H2O, CO, and CO2) and dust. Gases released in the interior are allowed to escape to the surface. It is shown that, depending on parameters, the interior may reach quite high temperatures (up to 180 K). The models suggest that Kuiper Belt objects are likely to lose the ices of very volatile species during early evolution; ices of less volatile species are retained in a surface layer, about 1 km thick. The models indicate that the amorphous ice crystallizes in the interior, and hence some objects may also lose part of the volatiles trapped in amorphous ice. Generally, the outer layers are far less affected than the inner part, resulting in a stratified composition and altered porosity distribution. These changes in structure and composition should have significant consequences for the short-period comets, which are believed to be descendants of Kuiper Belt objects.

To appear in: Icarus

For preprints, contact dina@planet.tau.ac.il

Observations of the Centaur 1999 UG5:
Evidence of a Unique Outer Solar System Surface
J.M. Bauer1, K.J. Meech1, Y.R. Fernandez1, T.L. Farnham2, and T.L. Roush3

1 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr. Honolulu, HI 96822, USA
2 University of Texas, Dept. of Astronomy, Austin, TX 78712, USA
3 Space Science Division, Planetary Systems Branch, MS 245-3, NASA Ames Research Center, Moffet Field, CA 94035-1000, USA

The outer Solar system body 1999 UG5 is a Centaur of medium brightness and slightly redder color when compared to other Centaurs. Similar to at least one fifth of the known Centaurs, it is a Saturn-crosser with a mean orbital distance between Saturn and Uranus. We present optical photometry data and NIR spectra obtained during September, November, and December, 2000. We find a rotation period of $13.41 \pm 0.04$ hours with an amplitude of $0.102
\pm 0.005$ mag, and a phase curve with a Lumme-Bowell G value of $-0.13 \pm 0.02$. BVRI colors are reported, and confirm the red spectral gradient observed previously. Our spectra reveal that this redward slope extends into NIR wavelengths and indicate possible localized differences in the surface composition.

To appear in: Publications of the Astronomical Society of the Pacific

For preprints, contact bauer@ifa.hawaii.edu

Photometric Light Curve for the Kuiper Belt Object 2000 EB173 on 78 Nights
Bradley E. Schaefer1 and David L. Rabinowitz2

1 Department of Astronomy, University of Texas, Austin TX 78712, USA
2 Department of Physics, Yale University, PO Box 208121, New Haven CT 06520-8121, USA

Kuiper Belt Objects (KBOs) are generally very faint and cannot in practice be monitored with a well-sampled long-term light curve; so our discovery of the bright KBO 2000 EB173 offers an excellent opportunity for synoptic studies. We present a well-sampled photometric time series (77 R magnitudes and 29 V magnitudes on 78 nights) over a 225-day time span centered on the 2001 opposition. The light curve (corrected to the year 2001 opposition distance) varies from 19.11 to 19.39 mag with a single peak that is smooth, time symmetric, and coincident with opposition. All variations in the light curve are consistent with a linear opposition surge ( $R_{OPP} =
19.083 + 0.125 \alpha$, where $\alpha$ is the solar phase angle), while any rotational modulation must have a peak-to-peak amplitude of less than 0.097 mag. This is the first measured opposition surge for any KBO (other than Pluto). The V-R color is $0.63 \pm 0.02$, with no apparent variation with phase at the few percent level. With R=19.11 at opposition, 2000 EB173 remains the brightest known KBO and a prime target for future photometric and spectroscopic studies.

To appear in: Icarus

For preprints, contact schaefer@astro.as.utexas.edu
or on the web at http://arXiv.org/abs/astro-ph/0208261

On the Detectability of Lightcurves of Kuiper Belt Objects
P. Lacerda1 and J. Luu2

1 Leiden Observatory, University of Leiden, Postbus 9513, NL-2300 RA Leiden, Netherlands
2 MIT Lincoln Laboratory, 244 Wood Street, Lexington, MA 02420, USA

We present a statistical study of the detectability of lightcurves of Kuiper Belt objects (KBOs). Some Kuiper Belt objects display lightcurves that appear ``flat'', i.e., there are no significant brightness variations within the photometric uncertainties. Under the assumption that KBO lightcurves are mainly due to shape, the lack of brightness variations may be due to (1) the objects have very nearly spherical shapes, or (2) their rotation axes coincide with the line of sight. We investigate the relative importance of these two effects and relate it to the observed fraction of ``flat'' lightcurves. This study suggests that the fraction of KBOs with detectable brightness variations may provide clues about the shape distribution of these objects. Although the current database of rotational properties of KBOs is still insufficient to draw any statistically meaningful conclusions, we expect that, with a larger dataset, this method will provide a useful test for candidate KBO shape distributions.

To appear in: Icarus

For preprints, contact placerda@strw.leidenuniv.nl


Formation of Kuiper Belt Binaries

Peter Goldreich1, Yoram Lithwick1, and Re'em Sari1

1 Theoretical Astrophysics, Caltech 130-33, Pasadena, CA 91125 USA

Submitted to: Nature

For preprints, contact yoram@tapir.caltech.edu
or on the web at http://arXiv.org/abs/astro-ph/0208490


Out on The Edge

W.B. McKinnon1

1 Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, Saint Louis, MO 63130, USA

Published in: Nature, 418, 135 (2002)

For preprints, contact mckinnon@levee.wustl.edu

Focus on Education: Striking Kuiper Belt Gold

Jodi Asbell-Clarke1

1 TERC, 2067 Massachusetts Avenue, Cambridge, MA 02140, USA

Published in: Mercury, 31, 13 (2002)

For preprints, contact Jodi_Asbell-Clarke@terc.edu

Dusty Rings: Signposts of Recent Planet Formation

Scott J. Kenyon1 and Benjamin C. Bromley2

1 Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138, USA
2 Department of Physics, University of Utah, 201 JFB, Salt Lake City, UT 84112, USA

To appear in: The Astrophysical Journal Letters

For preprints, contact skenyon@cfa.harvard.edu
or on the web at http://arXiv.org/abs/astro-ph/0208155


On the Initial Thermal Evolution of Kuiper Belt Objects

W.B. McKinnon1

1 Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, Saint Louis, MO 63130, USA

To appear in: Proceedings of Asteroids, Comets, Meteors 2002

For preprints, contact mckinnon@levee.wustl.edu

The above submission reminded me that abstracts of ACM presentations are available at:

The DPS meeting will be held in Birmingham, Alabama, USA on October 6-11
Details are available at: http://csem.engin.umich.edu/dps/
The meeting program shows the following Kuiper belt related sessions:


Modern Celestial Mechanics: Aspects of Solar System Dynamics
A. Morbidelli1

1 Observatoire de la Côte d'Azur, B.P. 4229, 06304 Nice Cedex 4, France

In the last 20 years celestial mechanics has achieved spectacular results on the structure and evolution of our solar system. With a solid theoretical basis this book describes recent results on solar system dynamics, with emphasis on planets and small bodies. It begins by presenting the fundamental concepts of Hamiltonian systems theory, necessary to work at ease in celestial mechanics. Celestial mechanics itself is then considered, including the secular motion of planets and small bodies and mean motion resonant dynamics. Modern Celestial Mechanics will be of interest to graduate students and researchers of astronomy and astrophysics.


  1. Elementary Celestial and Hamiltonian Mechanics
  2. Quasi-Integrable Hamiltonian Systems
  3. Kam Tori
  4. Single Resonance Dynamics
  5. Numerical Tools for the Detection of Chaos
  6. Interactions among Resonances
  7. Secular Dynamics of The Planets
  8. Secular Dynamics of Small Bodies
  9. Mean Motion Resonances
  10. Three-Body Resonances
  11. Secular Dynamics inside Mean Motion Resonances
  12. Global Dynamical Structure of the Belts of Small Bodies

Published in: Advances in Astronomy and Astrophysics, Volume 5
(ed. Taylor & Francis; London and New York)

Author contact morby@obs-nice.fr
Available for purchase on the web at http://www.tandf.co.uk/

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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Joel Parker