Distant EKOs, Issue #35  (May 2004)


News & Announcements
Abstracts of 9 Accepted Papers
Titles of 3 Submitted Papers
Titles of 3 Other Papers of Interest
Titles of 6 Conference Contribution
Newsletter Information


2003 VB12 (Sedna) has a long lightcurve of 20-50 days, making it the slowest rotating object in the solar system after Mercury and Venus. One explanation is that it is a binary, and the rotation has been regulated by a companion. However, recent HST observations did not detect a satellite. http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/14/

There were 15 new TNO discoveries announced since the previous issue of Distant EKOs:

2003 WS184, 2004 DJ71, 2004 DK71, 2004 DL71, 2004 DM71, 2004 EQ95, 2004 ER95, 2004 ES95, 2004 ET95, 2004 EU95, 2004 EV95, 2004 EW95, 2004 EO95, 2004 EP95, 2004 GV9

and no new Centaur/SDO discoveries.

Objects recently assigned numbers:

1997 CS29 = (79360)
1999 CP133 = (79969)
1999 DF9 = (79983)
1999 CC158 = (79978)
2000 CM105 = (80806)
2000 YW134 = (82075)
2001 FM185 = (82157)
2001 FP185 = (82158)
2001 FZ173 = (82155)
2002 GO9 = (83982)
2002 TC302 = (84522)
2002 VR128 = (84719)
2003 VS2 = (84922)

Current number of TNOs: 789 (and Pluto & Charon, and 12 other TNO binary companions)
Current number of Centaurs/SDOs: 149
Current number of Neptune Trojans: 1

Out of a total of 939 objects:
   471 have measurements from only one opposition
     339 of those have had no measurements for more than a year
       191 of those have arcs shorter than 10 days
(for more details, see: http://www.boulder.swri.edu/ekonews/objects/recov_stats.gif)


Discovery of a Candidate Inner Oort Cloud Planetoid
M.E. Brown1, C.A. Trujillo2, and D. Rabinowitz3

1 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
2 Gemini Observatory, 670 N. A'ohoku Place, Hilo, Hawaii, 96720, USA
3 Physics Department, Yale University, New Haven, CT 06520-8120, USA

We report the discovery of the minor planet 2003 VB12 (popularly named Sedna), the most distant object ever seen in the solar system. Pre-discovery images from 2001, 2002, and 2003 have allowed us to refine the orbit sufficiently to conclude that 2003 VB12 is on a highly eccentric orbit which permanently resides well beyond the Kuiper belt with a semimajor axis of 480$\pm$40 AU and a perihelion of 76$\pm$4 AU. Such an orbit is unexpected in our current understanding of the solar system, but could be the result of scattering by a yet-to-be-discovered planet, perturbation by an anomalously close stellar encounter, or formation of the solar system within a cluster of stars. In all of these cases a significant additional population is likely present, and in the two most likely cases 2003 VB12 is best considered a member of the inner Oort cloud, which then extends to much smaller semimajor axes than previously expected. Continued discovery and orbital characterization of objects in this inner Oort cloud will verify the genesis of this unexpected population.

To appear in: The Astrophysical Journal Letters (2004 August 10)

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

KBO Binaries: How Numerous Were They?
J. -M. Petit1 and O. Mousis1

1 Observatoire de Besançon, B.P. 1615, 25010, Besançon Cedex, France

Given the large orbital separation and high satellite-to-primary mass ratio of all known Kuiper Belt Object (KBO) binaries, it is important to reassess their stability as bound pairs with respect to several disruptive mechanisms. Besides the classical shattering and dispersing of the secondary due to a high-velocity impact, we consider the possibility that the secondary is kicked off its orbit by a direct collision of a small impactor, or that it is gravitationally perturbed due to the close approach of a somewhat larger TNO.

Depending on the values for the size/mass/separation of the binaries that we used, 2 or 3 of the 9 pairs can be dispersed in a timescale shorter than the age of the solar system in the current rarefied environment. A contemporary formation scenario could explain why we still observe these binaries, but no convincing mechanism has been proposed to date. The primordial formation scenarios, which seem to be the only viable ones, must be revised to increase the formation efficiency in order to account for this high dispersal rate. For the reference current KBO population, objects like the large-separation KBO binaries 1998 WW31 or 2001 QW322 must have been initially an order of magnitude more numerous.

If the KBO binaries are indeed primordial, then we show that the mass depletion of the Kuiper belt cannot result from collisional grinding, but must rather be due to dynamical ejection.

Published in: Icarus, 168, 409 (2004 April)

For preprints, contact petit@obs-besancon.fr

Kepler and the Kuiper Belt
B. Scott Gaudi1

1 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA

The proposed field-of-view of the Kepler mission is at an ecliptic latitude of $\sim 55^\circ$, where the surface density of scattered Kuiper Belt Objects (KBOs) is a few percent that in the ecliptic plane. The rate of occultations of Kepler target stars by scattered KBOs with radii r>10 km is $\sim 10^{-6}$ to 10-4 per star per year, where the uncertainty reflects the current ignorance of the thickness of the scattered KBO disk and the faint-end slope of their magnitude distribution. These occultation events will last only $\sim$0.1% of the planned texp=15 minute integration time, and thus will appear as single data points that deviate by tiny amounts. However, given the target photometric accuracy of Kepler, these deviations will nevertheless be highly significant, with typical signal-to-noise ratios of $\sim$10. I estimate that 1-20 of the 105 main-sequence stars in Kepler's field-of-view will exhibit detectable occultations during its four-year mission. For unresolved events, the signal-to-noise of individual occultations scales as texp-1/2, and the minimum detectable radius could be decreased by an order of magnitude to $\sim$1 km by searching the individual 3-second readouts for occultations. I propose a number of methods by which occultation events may be differentiated from systematic effects. Kepler should measure or significantly constrain the frequency of highly-inclined, $\sim$10 km-sized KBOs.

To appear in: The Astrophysical Journal

For preprints, contact sgaudi@cfa.harvard.edu

Planetary Migration in a Planetesimal Disk:
Why did Neptune Stop at 30 AU?
Rodney S. Gomes1, Alessandro Morbidelli2, and Harold F. Levison3

1 GEA/OV/UFRJ and ON/MCT Ladeira do Pedro Antônio, 43 - Centro, 20.080-090 Rio de Janeiro, RJ, Brazil
2 Observatoire de la Côte d'Azur, Nice, France
3 Southwest Research Institute, Boulder, Colorado, USA

We study planetary migration in a gas-free disk of planetesimals. In the case of our Solar System we show that Neptune could have had either a damped migration, limited to a few AUs, or a forced migration up to the disk's edge, depending on the disk's mass density. We also study the possibility of runaway migration of isolated planets in very massive disk, which might be relevant for extra-solar systems. We investigate the problem of the mass depletion of the Kuiper belt in the light of planetary migration and conclude that the belt lost its pristine mass well before that Neptune reached its current position. Therefore, Neptune effectively hit the outer edge of the proto-planetary disk. We also investigate the dynamics of massive planetary embryos embedded in the planetesimal disk. We conclude that the elimination of Earth-mass or Mars-mass embryos originally placed outside the initial location of Neptune also requires the existence of a disk edge near $30\,$AU.

To appear in: Icarus

For preprints, contact rodney@ov.ufrj.br

Comparative Study of the 2:3 and 3:4 Resonant Motion with Neptune: An Application of Symplectic Mappings and Low Frequency Analysis
T. Kotoulas1 and G. Voyatzis1

1 Department of Physics, University of Thessaloniki, 54124 Thessaloniki, Greece

The 2:3 and 3:4 exterior mean motion resonances with Neptune are studied by applying symplectic mapping models. The mappings represent efficiently Poincaré maps for the 3D elliptic restricted three body problem in the neighbourhood of the particular resonances. A large number of trajectories is studied showing the coexistence of regular and chaotic orbits. Generally, chaotic motion depletes the small bodies of the effective resonant region in both the 2:3 and 3:4 resonances. Applying a low frequency spectral analysis of trajectories, we determined the phase space regions that correspond to either regular or chaotic motion. It is found that the phase space of the 3:4 resonant motion is more chaotic than the 2:3 one.

Published in: Celestial Mechanics and Dynamical Astronomy, 88, 343 (2004 April)

For preprints, contact voyatzis@auth.gr

A Study of Trans-Neptunian Object 55636 (2002 TX300)
J.L. Ortiz1, A. Sota1, R. Moreno2, E. Lellouch3,
N. Biver3, A. Doressoundiram3, P. Rousselot4, P.J. Gutiérrez1,5,
I. Márquez1, R.M. González Delgado1, and V. Casanova1

1 Instituto de Astrofísica de Andalucia, CSIC, Apt 3004, 18080 Granada, Spain
2 I.R.A.M. 300 rue de la Piscine, 38406 St-Martin d'Hères Cedex, France
3 Observatoire de Paris, 5 place J. Jansen, 92195 Meudon, France
4 Observatoire de Besançon, B.P. 1615, F-25010 Besançon Cedex, France
5 Laboratoire d'Astrophysique de Marseille Traverse du Siphon. BP8-13376 Marseille Cedex 12, France

We report on physical properties of the bright Trans-Neptunian Object 2003 TX300 based on a large set of observations taken in different wavelength ranges. Broad band CCD observations aimed at studying the short-term rotational variability show a low amplitude periodic signal of $7.89 \pm 0.03$ hours. We cannot yet determine whether the lightcurve is single-peaked (i.e. the rotation period would be 7.89 hr) or double-peaked (i.e. the actual spin period would be 15.78 hr). From a sinusoidal fit, the peak to peak amplitude of the brightness changes is $0.09 \pm 0.08$ mag. If the brightness changes are due to irregular shape, this amplitude implies a minimum axial ratio of 1.09. BVRI photometry indicates similar colors as other large Kuiper Belt members, with $B-V = 0.64 \pm 0.04$, $V-R
= 0.40 \pm 0.07$, and $R-I = 0.22 \pm 0.05$. Thermal observations at 250 GHz (1.2 mm) result in no confident detection of the body, with a measured flux of $0.22 \pm 0.51$ mJy.

Combining all the data and using the same thermophysical model as in Lellouch et al. (A&A, 391, 1133) we find (at a $3\sigma$ confidence level) a lower limit for the geometric albedo (pv>0.06) and an upper limit for the size of this object (D<1110 km). A more relaxed $2\sigma$ confidence level implies a diameter D<907 km and an albedo pv>0.08, which is significantly higher than the typical 0.04 cometary value and also higher than that of Varuna.

To appear in: Astronomy and Astrophysics

For preprints, contact ortiz@iaa.es

Initial Orbit Determination for Distant Objects
Leif Kahl Kristensen1

1 Department of Physics and Astronomy, University of Aarhus, Ny Munkegade 520, DK-8000 Aarhus C, Denmark

Initial orbit determination for distant objects can be made a simple linear problem with explicit solutions. This is similar to stellar parallax work, with very difficult observations but simple computations. A very simple procedure for computing ephemerides for distant objects is proposed. The optimum distribution of observations in time and regions is investigated. The problem of double solutions, linking, elongation, and latitude, and accuracy of elements are also discussed.

Published in: The Astronomical Journal, 127, 2424 (2004 April)

For preprints, contact lkk@phys.au.dk

A Highly-automated Moving Object Detection Package
J.-M. Petit1, M. Holman2, H. Scholl3, J. Kavelaars4 and B. Gladman3,5

1 Observatoire de Besançon, B.P. 1615, 25010, Besançon Cedex, France
2Harvard-Smithsonian Center for Astrophysics, MS-18, 60 Garden Str, Cambridge, MA 02138, USA
3Observatoire de la Côte d'Azur, BP 4229, 06304 Nice cedex 04, France
4National Research Council Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, B.C. V9E 2E7, Canada
5Currently: Dept. of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1, Canada

With the deployment of large CCD mosaic cameras and their use in large-scale surveys to discover Solar System objects, there is a need for a fast detection algorithms that can handle large data loads in a nearly automatic way. We present here an algorithm that we have developed. Our approach, by using two independent detection algorithms and combining the results, maintains high efficiency while producing low false detection rates. These properties are crucial to in order to reduce the operator time associated with searching these huge data sets. We have used this algorithm on two different mosaic data sets obtained using the CFH12K camera at CFHT. Comparing the detection efficiency and false-detection rate of each individual algorithm with the combination of both, we show that our approach decreases the false detection rate by a factor of a few hundred to a thousand, while decreasing the `limiting magnitude' (where the detection rate drops to 50%) by only 0.1-0.3 magnitudes. The limiting magnitude is similar to that of a human operator blinking the images. Our full pipeline also characterizes the magnitude efficiency of the entire system by implanting artificial objects in the data set. The detection portion of the package is publicly available.

Published in: MNRAS, 347, 471 (2004 January)

For preprints, contact petit@obs-besancon.fr

High-eccentricity Trans-Neptunian Objects as a Source of Jupiter-family Comets
V.V. Emel'yanenko1, D.J. Asher2, and M.E. Bailey2

1 South Ural University, Chelyabinsk, 454080, Russia
2 Armagh Observatory, College Hill, Armagh, BT61 9DG, U.K.

The dynamical evolution of trans-Neptunian objects (TNOs) to the inner Solar system is investigated. The study is based on the observed sample of high-eccentricity TNOs with perihelia in the near-Neptune region, using a procedure to take account of observational biases. It is shown that observations favour TNOs in high-eccentricity orbits as the main source of Jupiter-family (JF) comets. The relative fraction of objects captured per year from the near-Neptune region to JF comets with perihelion distances $q\!<\!1.5$AU is estimated as 0.2 x 10-10. The maximum lifetime of typical JF comets with $q\!<\!1.5$AU is approximately 200 revolutions. Based on the observed population of JF comets, there should be $\sim$1010 TNOs of cometary size in high-eccentricity orbits with $28\!<\!q\!<\!35.5$au. If this population originated 4.5Gyr ago, the primordial number must have been at least 20 times as large as the present one.

To appear in: Monthly Notices of the Royal Astronomical Society, 350, 161

Preprints available on the web at http://star.arm.ac.uk/preprints/


Regarding the Accretion of 2003 VB12 (Sedna) and Like Bodies in Distant Heliocentric Orbits

S.A. Stern1

1 Dept. of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 400, Boulder, CO 80302 USA

Submitted to: The Astronomical Journal

For preprints, contact astern@swri.edu
or on the web at http://arxiv.org/abs/astro-ph/0404525

The Size Distribution of Kuiper Belt Objects

S. J. Kenyon1 and B. 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

Submitted to: The Astronomical Journal

Internal Properties of Kuiper Belt Objects Derived from Hubble Space Telescope Lightcurve Observations

David E. Trilling1 and Gary M. Bernstein1

1 Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33rd St., Philadelphia, PA 19104, USA

Submitted to: The Astronomical Journal

For preprints, contact trilling@astro.upenn.edu


The Kuiper Belt

Michael E. Brown1

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

Published in: Physics Today, 57, 49 (2004 April)

The Formation of the Solar System by Gravitational Instability: Prediction of a New Planet or Another Kuiper-type Belt

Evgeny Griv1 and Michael Gedalin2

1 Department of Physics, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel

Available on the web at http://arxiv.org/abs/astro-ph/0403376

Dynamical Effects of the Radial Galactic Tide on an Oort Cloud of Comets for Stars with Different Masses and Varying Distances from the Galactic Center

Marco Masi1

1 Dipartimento di Fisica G. Galilei, Padova, Italy

For preprints, contact marco.masi@spiro.fisica.unipd.it
or on the web at http://arxiv.org/abs/astro-ph/0403599


There were several Kuiper belt presentations at the recent 35th Meeting of the AAS Division on Dynamical Astronomy, which was held on 2004 April 20-23 in Canes, France. The following are the papers that I gleaned from the online abstracts, though there some others may be relevant to aspects of Kuiper belt research: http://www.aas.org/publications/baas/v36n2/dda04/SL.htm

Planetary Migration in a Planetesimal Disk: Why did Neptune Stop at 30 AU?
A. Morbidelli (OCA- Nice), R. Gomes (ON- Rio de Janeiro), H. Levison (SWRI- Boulder)

Could 2003 VB12 (Sedna) Have Formed In Situ Within A Massive, Disk-Like Extension of the Kuiper Belt?
S. A. Stern (SwRI)

An Impact Formation of Pluto-Charon
R.M. Canup (Southwest Research Institute)

Dynamical Evolution and End States of Scattered Disk Objects
J.A. Fernandez, T. Gallardo (Depto. Astronomia, Facultad de Ciencias, Montevideo, Uruguay), A. Brunini (Facultad de Ciencias Astronomicas y Geofisicas, La Plata, Argentina - CONICET)

The Formation of High Inclination Trans-Neptunian Objects
R.S. Gomes (GEA/OV/MCT & ON/MCT)

The Scattered Disk as a Source of Halley-Type Comets
H.F. Levison (SwRI), M.J. Duncan (Queen's U), L Dones (SwRI)

Neptune's Smooth Migration into a Hot Kuiper Belt
J.M. Hahn (Saint Mary's University), R. Malhotra (University of Arizona)

Periodic Orbits in the Exterior Resonances 1/2,1/3 and 1/4 with Neptune
T. Kotoulas, G. Voyatzis (University of Thessaloniki)

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.

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Joel Parker 2004-05-10