Distant EKOs, Issue #23  (May 2002)


News & Announcements
Abstracts of 7 Accepted Papers
Titles of 1 Submitted Paper
Titles of 1 Conference Contribution
Newsletter Information


The discovery that 2000 CF105 is a binary TNO was announced in IAUC 7857 by Noll et al.. The components differ in brightness by $\Delta V=0.87$ mag and $\Delta I=0.56$ mag, with a separation of 0.78 arcsec ($\sim$23,000 km at 41.32 AU).
IAUC: http://cfa-www.harvard.edu/iauc/07800/07857.html

The program for ``From Here to Pluto-Charon: A New Horizons PKB Mission Workshop'' (to be held May 20-21 in Boulder, Colorado) is now available online at:

As the number of Kuiper belt-related objects with well-known orbits grows, are you starting to no longer recognize references to your favorite objects? A new table of cross references between provisional designations, numbers, and names has been added to the Objects page at the Distant EKOs website: http://www.boulder.swri.edu/ekonews/objects/

There were 13 new TNO discoveries announced since the previous issue of the Distant EKOs Newsletter:

2001 DU108, 2001 DV108, 2001 YJ140, 2002 CY248, 2002 CC249, 2002 FU6, 2002 FV6, 2002 FW6, 2002 FX6, 2002 CC251, 2002 CD251, 2002 CE251, 2002 FP7

and 11 new Centaur/SDO discoveries:

2001 YH140, 2002 CA249, 2002 CB249, 2002 CZ248, 2001 FJ194, 2001 FK194, 2001 FL194, 2001 FM194, 2001 FN194, 2002 GB10, 2002 GO9

Reclassified objects:
2001 FL194 (SDO $\rightarrow$ TNO)
2001 KP77 (SDO $\rightarrow$ TNO)
2001 UQ18 (TNO $\rightarrow$ SDO)
2001 UR163 (TNO $\rightarrow$ SDO)
2001 XA255 (Centaur $\rightarrow$ SDO)
2001 XP254 (SDO $\rightarrow$ TNO)
2001 XS254 (SDO $\rightarrow$ TNO)
2002 CR46 (Centaur $\rightarrow$ SDO)

Objects recently assigned numbers:
1999 HB12 = (38084)
1999 HX11 = (38083)
2000 EB173 = (38628)

Objects recently assigned names:
1998 WH24 = Chaos
2001 KX76 = Ixion

Current number of TNOs: 529 (and Pluto & Charon, and 7 other TNO binary companions)
Current number of Centaurs/SDOs: 110


Colors of Minor Bodies in the Outer Solar System:
A Statistical Analysis
O.R. Hainaut1 and A.C. Delsanti1,2

1 European Southern Observatory, Casilla 19001, Santiago, Chile
2 Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France

We present a compilation of all available colors for 104 Minor Bodies in the Outer Solar System (MBOSSes); for each object, the original references are listed. The measurements were combined in a way that does not introduce rotational color artifacts. We then derive the slope, or reddening gradient, of the low resolution reflectance spectra obtained from the broad-band color for each object.

A set of color-color diagrams, histograms and cumulative probability functions are presented as a reference for further studies, and are discussed. In the color-color diagrams, most of the objects are located very close to the ``reddening line'' (corresponding to linear reflectivity spectra). A small but systematic deviation is observed toward the I band indicating a flattening of the reflectivity at longer wavelengths, as expected from laboratory spectra. A deviation from linear spectra is noticed toward the B for the bluer objects; this is not matched by laboratory spectra of fresh ices, possibly suggesting that these objects could be covered with extremely evolved/irradiated ices. Five objects (1995 SM55, 1996 TL66, 1999 OY3, 1996 TO66 and (2060) Chiron) have almost perfectly solar colors; as two of these are known or suspected to harbour cometary activity, the others should be searched for activity or fresh ice signatures. In the color-color diagrams, 1994 ES2, 1994 EV3, 1995 DA2 and 1998 HK151 are located very far from the main group of objects; it is suspected that this corresponds to inaccurate measurements and not intrinsically strange objects.

The color distributions were analyzed as functions of the orbital parameters of the objects and of their absolute magnitude. No significant correlation is observed, with the following exceptions: Cubewanos with low orbital excitation (low i, e and/or ${\cal E} =
\sqrt{e^2 + \sin^2 i}$), and therefore experiencing on average fewer and less violent collisions have significantly redder colors; Cubewanos with faint absolute magnitude M(1,1) tend to be redder than the others, while Plutinos present the opposite trend.

The color distribution of the various MBOSS classes are analyzed and compared using generic statistic tools. The comets were found to be significantly bluer than the other MBOSSes.

Finally, we compare the various 1D and 2D color distributions to simple models, in order to throw some light on the question of the bimodality of MBOSS color distributions. It is found that with the current data set, all color distributions are compatible with simple, continuous distribution models, while some color distributions are not compatible with simple bimodal distribution models. The tables and complete set of figures corresponding the up-to-date database are available on the web at http://www.sc.eso.org/~ohainaut/MBOSS

To appear in: Astronomy and Astrophysics

For preprints, contact ohainaut@eso.org
or on the web at http://www.sc.eso.org/~ohainaut/MBOSS

Bicolour lightcurve of TNO 1996 TO66 with the ESO-VLT
T. Sekiguchi1,2, H. Boehnhardt1, O.R. Hainaut1, and C.E. Delahodde1

1 European Southern Observatory(ESO), Casilla 19001, Alonso de Cordova 3107, Vitacura, Santiago, Chile
2 Graduate University for Advanced Studies, National Astronomical Observatory, Osawa 2-21-1, Mitaka, Japan

We performed high resolution imaging of 1996 TO66 in V and R bands to verify and monitor the lightcurve change, to address a colour change over a rotation and to search for a cometary activity. No activity was detected at the 29 mag/sq.arcsec level with 5400 s integration time with the ESO-VLT. Combining the data in Nov. and Dec. 1999, we obtained a complete rotation period coverage. The lightcurve was a single-peaked, with an amplitude of 0.21 mag in R. The (V - R) colour displays the inhomogeneity of TNO surface. TNO's patchy surface may be cause the intensity change of water absorption feature in near-IR spectra. These observations can be the starting points for a challenging work of surface mapping of TNOs.

Published in: Astronomy & Astrophysics, 385, 281 (2002 April)

For preprints, contact t.sekiguchi@nao.ac.jp

Infrared Spectroscopy of the Largest Known
Trans-Neptunian Object 2001 KX
J. Licandro1, F. Ghinassi1, and L. Testi2

1 Centro Galileo Galilei & Telescopio Nazionale Galileo, P.O.Box 565, E-38700, S/C de La Palma, Tenerife, Spain
2 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy

We report complete near-infrared (0.9-2.4 $\mu$m) spectral observations of the largest know trans-neptunian objects (TNO) 28976 = 2001 KX76 taken in two different nights using the new Near Infrared Camera Spectrometer (NICS) attached to the 3.56m Telescopio Nazionale Galileo (TNG). The spectra are featureless and correspond to a neutral colored object. Our observations indicate that the surface of 2001 KX76 is probably highly evolved due to long term irradiation, and that collisional resurfacing processes have not played an important role in its evolution.

To appear in: Astronomy & Astrophysics

Preprint by e-mail to licandro@tng.iac.es
or on the web at http://xxx.lanl.gov/abs/astro-ph/0204104

The Binary Kuiper Belt Object 1998 WW31
Christian Veillet1, Joel Wm. Parker2, Ian Griffin3,
Brian Marsden
4, Alain Doressoundiram5 , Marc Buie6,
David J. Tholen
7, Michael Connelley7, and Matthew J. Holman4

1 Canada France Hawaii Telescope, Kamuela, Hawaii 96743, USA
2 Southwest Research Institute, Boulder, Colorado 80302, USA
3 Space Telescope Science Institute, Baltimore, Maryland 21218, USA
4 Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA
5 Observatoire de Paris, Place Jules Janssen, F-92 195 Meudon Cedex, France
6 Lowell Observatory, 1400 Mars Hill Road, Flagstaff, Arizona 8600, USA
7 Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA

The recent discovery of a binary asteroid during a spacecraft fly-by generated keen interest, because the orbital parameters of binaries can provide measures of the masses, and mutual eclipses could allow us to determine individual sizes and bulk densities. Several binary near-Earth, main-belt and Trojan asteroids have subsequently been discovered. The Kuiper belt--the region of space extending from Neptune (at 30 astronomical units) to well over 100 AU and believed to be the source of new short-period comets--has become a fascinating new window onto the formation of our Solar System since the first member object, not counting Pluto, was discovered in 1992. Here we report that the Kuiper-belt object 1998 WW31 is binary with a highly eccentric orbit (eccentricity $e \approx 0.8$) and a long period (about 570 days), very different from the Pluto/Charon system, which was hitherto the only previously known binary in the Kuiper belt. Assuming a density in the range of 1 to 2 g cm-3, the albedo of the binary components is between 0.05 and 0.08, close to the value of 0.04 generally assumed for Kuiper-belt objects.

Published in: Nature, 416, 711 (2002 April 18)

For preprints, contact veillet@cfht.hawaii.edu
or on the web at http://oposite.stsci.edu/pubinfo/pr/2002/04/

Pluto and Charon: Formation, Seasons, Composition
M.E. Brown1

1 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125 USA

Pluto and Charon, once thought to be a singular system in an odd orbit at the edge of the solar system, are now known as members of a vast population of icy bodies beyond Neptune. Models for the occurrence of the odd orbit and formation of these bodies in the context of the total population are reviewed. Pluto's orbital characteristics, coupled with the existence of volatiles on the surface, suggest that large scale seasonal change should occur on the surface. Models of seasonal variability are discussed, past and current observations are examined for evidence of variability, and a strawman model of seasonal changes is proposed. Finally, recent observations of the surface composition of Charon are discussed and compared to observations of other similarly-sized icy bodies in the outer solar system.

Published in: Annual Review of Earth and Planetary Science, 30, 307 (2002)

Preprints on the web at http://www.gps.caltech.edu/~mbrown/papers

Migration of Giant Planets in a Time-dependent Planetesimal Accretion Disc
A. Del Popolo1,2,3 and Y. Eksi2

1 Dipartimento di Matematica, Università Statale di Bergamo, Piazza Rosate, 2 - I 24129 Bergamo, Italy
2 Bo $\breve{g}azi$çi University, Physics Department, 80815 Bebek, Istanbul, Turkey
3 Feza Gürsey Institute, P.O. Box 6 Çengelköy, Istanbul, Turkey

In this paper, we further develop the model for the migration of planets introduced in Del Popolo et al. (2001). We first model the protoplanetary nebula as a time-dependent accretion disc and find self-similar solutions to the equations of the accretion disc that give to us explicit formulas for the spatial structure and the temporal evolution of the nebula. These equations are then used to obtain the migration rate of the planet in the planetesimal disc and to study how the migration rate depends on the disc mass, on its time evolution and on some values of the dimensionless viscosity parameter $\alpha$. We find that planets that are embedded in planetesimal discs, having total mass of $10^{-4}-10^{-1}~M_{\odot}$, can migrate inward a large distance for low values of $\alpha$ (e.g., $\alpha \simeq 10^{-3}-10^{-2}$) and/or large disc mass and can survive only if the inner disc is truncated or because of tidal interaction with the star. Orbits with larger a are obtained for smaller value of the disc mass and/or for larger values of $\alpha$. This model may explain several orbital features of the recently discovered giant planets orbiting nearby stars.

Published in: Monthly Notices of the Royal Astronomical Society, 332, 485

For preprints, contact adelpop@unibg.it

Modern Integrations of Solar System Dynamics
A. Morbidelli 1

1 Observatoire de la Côte d'Azur, 06304 Nice Cedex 4, France

Until the early 1990s, numerical simulations of Solar System dynamics were done using accurate but slow integrators. The typical timescales were on the order of a million years, apart from exceptions achieved by considering averaged equations or using specifically designed supercomputers. In the last decade, new numerical integration methods for Solar System dynamics have been introduced. The mixed variable symplectic method (Wisdom & Holman 1991) has permitted the study, in the absence of close encounters, of the evolution of planets and small bodies on timescales comparable to the age of the Solar System. The regularized mixed variable scheme (Levison & Duncan 1994) has allowed the compilation of statistics on the evolution of thousands of near-Earth asteroids and comets, from their source regions to their dynamical elimination. The Symba and the Mercury codes (Duncan et al. 1998, Chambers 1999), which treat close encounters between massive bodies in a symplectic way, have permitted the simulations of planetary accretion and of the early phase of the highly chaotic evolution of the Solar System. This paper reviews the most exciting results obtained with these new integrators. Emphasis is given to the conceptual steps that these works represent in our understanding of Solar System dynamics.

Published in: Annual Review of Earth and Planetary Science, 30, 89 (2002)

For preprints, contact morby@obs-nice.fr


A Collisional Family in the Classical Kuiper Belt

Eugene Chiang1

1 UC Berkeley Astronomy, 601 Campbell Hall, Berkeley CA 94720, USA

Submitted to: The Astrophysical Journal Letters

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


Kuiper Belt Dust: Spatial Distribution and Spectral Energy Distribution

Amaya Moro-Martín1 and Renu Malhotra2

1 Steward Observatory, 933 N. Cherry Avenue, Tucson, AZ 85721, USA
2 University of Arizona, 1629 E. University Boulevard, Tucson, AZ 85721, USA

To appear in: ASP Conference Series (Debris Disks and the Formation of Planets: A Symposium in Memory of Fred Gillet)

For preprints, contact amaya@as.arizona.edu

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:

A LaTeX template for submissions is appended to each issue of the newsletter, and is sent out regularly to the e-mail distribution list. Please use that template, and send your submission to:
The Distant EKOs Newsletter is available on the World Wide Web at:
Recent and back issues of the Newsletter are archived there in various formats. The web pages also contain other related information and links.

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