NASA has selected New Horizons led by Southwest Research Institute to
proceed with the design (Phase B) of a mission to the Pluto and the
Kuiper belt. The mission will launch in January 2006, fly by Jupiter in
March 2007, nominally fly by Pluto-Charon in July, 2016, and visit up to
three TNOs in the following five years (about 1 every 20 months, on
average). New Horizons will hold a public 2.5-day workshop in Boulder in
May regarding mission science and participation by community members
(details will be available in the next issue of the Newsletter). More
information about the project can be found at:
Researchers interested in collaboration can contact the project PI, Alan Stern.
The discovery that 1999 TC36 is a binary TNO was announced in IAUC 7787 by
Trujillo and Brown. The components differ in brightness by 2.21 mag,
with a separation of 0.37 arcsec.
More information at:
The Kuiper belt community panel for the Solar System Decadal Survey has
produced their white paper report. It is available online at:
The report discusses the current status of the field and lists the key science questions to be answered in the next decade, regarding: the dynamical structure of the Kuiper belt, the different types/classes, their physical composition and structure, and implications about formation of the outer solar system. The paper makes recommendations for programs to answer these questions that include support for: dedicated ground-based observatories to obtain a well-measured and unbiased sample of 5000 TNOs and measure physical properties of many of them, prompt development and launch of a space mission for direct exploration of Pluto and the Kuiper belt, and increased theoretical and laboratory studies.
There were 6 new TNO discovery announced since the previous issue of the Distant EKOs Newsletter:
2001 DQ108, 2001 XR254, 2001 XU254, 2001 XV254, 2001 XW254, 2001 XX254
and 5 new Centaur/SDO discoveries:
2001 XP254, 2001 XQ254, 2001 XS254, 2001 XT254, 2001 XA255
2000 SY370 (TNO SDO)
2000 WM183 (TNO SDO)
2000 YY1 (TNO SDO)
2000 YW134 (TNO SDO)
Objects recently assigned numbers:
1999 UG5 = 31824
2001 PT13 = 32532
2000 YW134 = 2001 XG201
Current number of TNOs: 489 (and Pluto & Charon, and four other TNO binary companions)
Current number of Centaurs/SDOs: 92
A Kuiper belt observer workshop was held at the DPS meeting on November 26. Much of the discussion centered on current survey projects, their status and expected discovery and recovery rates, and the need for a much larger scale of recovery efforts. It was pointed out repeatedly that follow-up observations necessary to obtain sufficiently well-determined orbital elements require significantly (roughly 5-6 times) more observing time than used for the discoveries. At least 25% of all Kuiper belt related objects are effectively lost or should be considered ``endangered.''
There was general agreement that more effort should be put into recoveries, and
that it would be helpful to somehow coordinate recovery observations by
improving communcation between groups, sharing online tools, etc., so that
effort is not needlessly duplicated. Some observers are developing web sites
that provide information complementary to that avaiable at the MPC (e.g., at
http://www.lowell.edu/users/buie/kbo/kbofollowup.html one can find
lists of TNOs that are prioritized by current uncertainty or ``need'' for
astrometric observation), but there is still no centralized facility for
observers to share their target lists during observing runs or communicate
details of recent successful and failed recovery observations.
Some groups have object-finding software that they will make publically
available. It is requested that if you have such software that you would
like to make avaiable to other observers, please send the information to EKOnews@boulder.swri.edu (along with a URL of the associated web page if available), and it will be advertised in a subsequent issue of the newsletter
and posted on the Distant EKOs software web page
It was also mentioned that, since the number of binary TNOs has suddenly blossomed, there is a strong motivation for observers to examine objects by eye to look for extended structure that may indicate binarity.
We have measured broadband optical BVR photometry of 24 Classical and Scattered Kuiper belt objects (KBOs), approximately doubling the published sample of colors for these classes of objects. We find a statistically significant correlation between object color and inclination in the Classical Kuiper belt using our data. The color and inclination correlation increases in significance after the inclusion of additional data points culled from all published works. Apparently, this color and inclination correlation has not been more widely reported because the Plutinos show no such correlation, and thus have been a major contaminant in previous samples. The color and inclination correlation excludes simple origins of color diversity, such as the presence of a coloring agent without regard to dynamical effects. Unfortunately, our current knowledge of the Kuiper belt precludes us from understanding whether the color and inclination trend is due to environmental factors, such as collisional resurfacing, or primordial population effects. A perihelion and color correlation is also evident, although this appears to be a spurious correlation induced by sampling bias, as perihelion and inclination are correlated in the observed sample of KBOs.
To appear in: The Astrophysical Journal Letters
For preprints, contact firstname.lastname@example.org
or by anonymous ftp to ftp://ftp.gps.caltech.edu/pub/chad/colorincl.ps
or on the web at
We present new time-resolved photometric observations of the bright trans-Neptunian object (20000) Varuna and use them to study the rotation period, shape, and color. In observations from 2001 February and April, we find a best-fit two-peaked lightcurve with period hr. The peak-to-peak photometric range in the R-band is mag. We find no rotational variation in colors over the m wavelength range. From the short double-peaked period and large amplitude we suggest that Varuna is an elongated, prolate body perhaps close in shape to one of the Jacobi ellipsoids. If so, the ratio of the axes projected into the plane of the sky is 1.5:1 and the density is near 1000 kg m-3. (20000) Varuna may be a rotationally distorted rubble pile, with a weak internal constitution due to fracturing by past impacts. The high specific angular momentum implied by our observations and recent detections of binary Trans-Neptunian Objects both point to an early, intense collisional epoch in which large Trans-Neptunian Objects were 100 times more abundant than now. In order to maintain a cosmochemically plausible rock:ice mass ratio 0.5, Varuna must be internally porous.
To appear in: The Astronomical Journal
For preprints, contact jewitt@IfA.Hawaii.Edu
or on the web at
This paper reviews coagulation models for planet formation in the Kuiper Belt, emphasizing links to recent observations of our and other solar systems. At heliocentric distances of 35-50 AU, single annulus and multiannulus planetesimal accretion calculations produce several 1000 km or larger planets and many 50-500 km objects on timescales of 10-30 Myr in a Minimum Mass Solar Nebula. Planets form more rapidly in more massive nebulae. All models yield two power law cumulative size distributions, with q = 3.0-3.5 for radii 10 km and for radii 1 km. These size distributions are consistent with observations of Kuiper Belt objects acquired during the past decade. Once large objects form at 35-50 AU, gravitational stirring leads to a collisional cascade where 0.1-10 km objects are ground to dust. The collisional cascade removes 80% to 90% of the initial mass in the nebula in 1 Gyr. This dust production rate is comparable to rates inferred for Lyr, Pic, and other extrasolar debris disk systems.
To appear in: Publications of the Astronomical Society of the Pacific (2002 March)
For preprints, contact email@example.com
or on the web at
We study the orbital evolutions of various systems of planetary embryos in the trans-Neptunian region, undergoing mutual scattering and perturbations from the giant planets. We show that about 15-20% of the original embryos should survive in the trans-Neptunian region at the current epoch. The orbital dispersion of the surviving embryos depends on their individual mass, so that only Lunar mass embryos could survive with semimajor axis smaller than 50 AU. In all cases we show by a Monte Carlo model that at least one of the surviving embryos should have been already discovered by one of the most effective Kuiper belt surveys. This implies that planetary embryos did not form in the trans-Neptunian region (or have been removed by some external and unknown mechanism). Therefore, we conclude that the Kuiper belt did not undergo self-excitation, unlike the asteroid belt. We also compute with the Monte Carlo model that a significant number (order 10) of Pluto-size bodies could exist only on very eccentric and long-periodic orbits, typical of the scattered disk, while the existence of about 30 bodies brighter than absolute magnitude 4 in the classical belt is compatible with the discovery of Varuna by the Spacewatch survey.
To appear in: Icarus
For preprints, contact A. Morbidelli firstname.lastname@example.org
or on the web at
The physical basis of chaos in the solar system is now better understood: in all cases investigated so far, chaotic orbits result from overlapping resonances. Perhaps the clearest examples are found in the asteroid belt. Overlapping resonances account for its Kirkwood gaps and were used to predict and find evidence for very narrow gaps in the outer belt. Further afield, about one new ``short-period'' comet is discovered each year. They are believed to come from the ``Kuiper Belt'' (at 40 AU or more) via chaotic orbits produced by mean-motion and secular resonances with Neptune. Finally, the planetary system itself is not immune from chaos. In the inner solar system, overlapping secular resonances have been identified as the possible source of chaos. For example, Mercury, in 1012 years, may suffer a close encounter with Venus or plunge into the Sun. In the outer solar system, three-body resonances have been identified as a source of chaos, but on an even longer time scale of 109 times the age of the solar system. On the human time scale, the planets do follow their orbits in a stately procession, and we can predict their trajectories for hundreds of thousands of years. That is because the mavericks, with shorter instability times, have long since been ejected. The solar system is not stable; it is just old!
Published in: Annual Review of Astronomy and Astrophysics, 39, 581 (2001)
For preprints, contact email@example.com
or on the web at
The dynamical systems of planet-belt interaction are studied by the fixed-point analysis and the bifurcation of solutions on the parameter space is discussed. For most cases, our analytical and numerical results show that the locations of fixed points are determined by the parameters and these fixed points are either structurally stable or unstable. In addition to that, there are two special fixed points: the one on the inner edge of the belt is asymptotically stable and the one on the outer edge of the belt is unstable. This is consistent with the observational picture of Asteroid Belt between the Mars and Jupiter: the Mars is moving stablely close to the inner edge but the Jupiter is quite far from the outer edge.
To appear in: International Journal of Bifurcation and Chaos
For preprints, contact firstname.lastname@example.org
or on the web at
We use a new multiannulus planetesimal accretion code to investigate the evolution of a planetesimal disk following a moderately close encounter with a passing star. The calculations include fragmentation, gas and Poynting-Robertson drag, and velocity evolution from dynamical friction and viscous stirring. We assume that the stellar encounter increases planetesimal velocities to the shattering velocity, initiating a collisional cascade in the disk. During the early stages of our calculations, erosive collisions damp particle velocities and produce substantial amounts of dust. For a wide range of initial conditions and input parameters, the time evolution of the dust luminosity follows a simple relation, . The maximum dust luminosity L0 and the damping time td depend on the disk mass, with and . For disks with dust masses of 1% to 100% of the `minimum mass solar nebula' (1-100 at 30-150 AU), our calculations yield 1-10 Myr, 1-2, = 1, and dust luminosities similar to the range observed in known `debris disk' systems, to 10-5. Less massive disks produce smaller dust luminosities and damp on longer timescales. Because encounters with field stars are rare, these results imply that moderately close stellar flybys cannot explain collisional cascades in debris disk systems with stellar ages of 100 Myr or longer.
To appear in: The Astronomical Journal (2002 March)
For preprints, contact email@example.com
or on the web at
To view an animation on the web, see
[This announcement appeared in the previous issue of Distant EKOs, with a typo in an e-mail address and without the meeting's web page address, which is given here. -- Ed.]
Symposium agenda outline:
I. History of the discovery
A. Protostellar disks: review w/emphasis on massive (Ae, Be) disks
B. Dynamics and lifetimes of protostellar disks and massive stars
C. Evidence and cautions re. ``falling evaporating bodies''
III. Debris disks
B. Latest observations of debris disks
C. Stellar ages (and how dicey it still is to determine them)
D. Young debris disks ( < few x 10 Myr) and their gas content
E. Old debris disks (few x 100's M yrs) and their dust content
IV. Descendants and connection to the Solar System
A. Characteristics of other planetary systems
B. Evidence in debris disk morphologies for planetary masses
C. Evolution of the Kuiper Belt and connection to Vega-like systems
D. Caution: history of our solar system may be quite untypical
V. Where do we go from here?
A. Observatories and observations
B. Theory/modeling required for making progress
Chairs of the scientific organizing committee:
Dana Backman: firstname.lastname@example.org, email@example.com
Larry Caroff: firstname.lastname@example.org
Chair of the local organizing committee:
Steve Strom: email@example.com
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.