Ethane ice has been detected on Pluto using the Cooled Infrared
Spectrograph/Camera (CISCO) instrument on the Subaru Telescope. The ethane
appears to be individual grains but is dissolved in the nitogen ice. Details
at:
http://www.subaru.naoj.org/outreach/press_releases/990719/
With this issue, Distant EKOs celebrates its first birthday with 289 subscribers in at least 23 countries. Thanks to all the readers and contributors for your support and feedback to make this a valuable communication tool for Kuiper Belt research.
There were 17 new EKO discoveries announced since the previous issue of the Distant EKOs Newsletter:
1999 DH8, 1999 HG12, 1999 HH12, 1999 HJ12, 1998 SN165, 1999 GS46, 1999 JH132, 1999 JJ132, 1999 JK132, 1999 KR16, 1999 KS16, 1999 KT16, 1999 KK17, 1999 KL17, 1999 OA4, 1999 OY3, 1999 OZ3,
It is possible that 1999 KS16 is a rediscovery of the ``lost'' object 1995 GA7 (see M.P.E.C. 1999-O36).
Also, a new Centaur was discovered: 1999 OX3
Current number of EKOs: 191 (and Pluto & Charon)
Current number of Centaurs: 15
We show that early stellar encounters can explain the high eccentricities and
inclinations observed in the outer part (>42AU) of the Edgeworth-Kuiper Belt
(EKB). We consider the proto-sun as a member of a stellar aggregation that
undergoes dissolution on a timescale 
yrs, such that the solar
nebula experiences a flyby encounter at pericenter distance (q) on the order
of 100AU. Using numerical simulations we show that a stellar encounter pumps
the velocity dispersion in the young solar nebula in the outer parts. In the
case of a nearly parabolic encounter with a solar-mass companion the velocity
dispersion at
is pumped up to such an extent that collisions
between planetesimals would be expected to become highly disruptive, halting
further growth of planetesimals. This has the consequence that planet
formation is forestalled in that region. We also find that a stellar encounter
with pericenter distance
-200AU could have pumped up the
velocity dispersion of EKB objects outside 42AU to the observed magnitude while
preserving that inside Neptune's 3:2 mean-motion resonance (located at 39.5AU).
This allows for the efficient capture of objects by the resonance during a
phase of orbital migration by proto-Neptune, which we also test with
simulations. We point out that such a stellar encounter generally affects the
dynamical and material structure of a protoplanetary disk and the planetesimal
distribution can remain imprinted with this signature over much of the main
sequence lifetime of the star. In particular, our results support the notion
that an analogous process has operated in some recently observed extrasolar
dust disks.
To appear in: The Astrophysical Journal
For preprints, contact ida@geo.titech.ac.jp
or on the web at
http://www.geo.titech.ac.jp/nakazawalab/ida/AJ.html
Emissivity and the Fate of Pluto's Atmosphere
J.A. Stansberry1 and R.V. Yelle2
1 Steward Observatory, University of Arizona, Tucson 85721
2 Physics and Astronomy, Northern Arizona University, Flagstaff 86011
We present a simplified model for seasonal changes in Pluto's
surface-atmosphere system. The model demonstrates the potential importance of
the solid-state phase transition between 
-N2 and 
-N2, and
the accompanying change in emissivity, for predicting the seasonal bulk of
Pluto's (and Triton's) atmosphere. Specifically, the model shows that under
simplified but not unreasonable assumptions Pluto may have nearly the same
atmospheric pressure at aphelion as it does now, near perihelion. The
emissivity change which accompanies the
-
phase change should
be included in the next generation of Pluto and Triton seasonal models for the
purposes of understanding the evolution of their atmospheres over seasonal and
climatic time-scales.
To appear in: Icarus
For preprints, contact stansber@as.arizona.edu
1 Lowell Observatory, 1400 W. Mars Hill Rd., Flagstaff AZ 86001
2 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson AZ 85721
3 Laboratoire de Planetologie de Grenoble, Batiment D de Physique, B.P. 53, 38041 Grenoble Cedex 9, France
We present new 1.20 to 2.35 
m spectra of satellites of Jupiter,
Saturn, and Uranus, and the rings of Saturn, obtained in 1995 and 1998
at Lowell Observatory. For most of the target objects, our data provide
considerable improvement in spectral resolution and signal-to-noise over
previously published data. Absorption bands with shapes characteristic
of low-temperature, hexagonal crystalline H2O ice dominate the spectra
of most of our targets in this wavelength range.
We make use of newly published temperature-dependent wavelengths and
relative strengths of H2O absorption bands to infer ice temperatures
from our spectra. These ice temperatures are distinct from temperatures
determined from thermal emission measurements or simulations of radiative
balances. Unlike those methods, which average over all terrains including
ice-free regions, our temperature-sensing method is only sensitive to the
ice component. Our method offers a new constraint which, combined with
other observations, can lead to better understanding of thermal properties
and textures of remote, icy surfaces. Ice temperatures are generally lower
than thermal emission brightness temperatures, indicative of the effects of
thermal inertia and segregation between ice and warmer, darker materials.
We also present the results of experiments to investigate possible changes
of water ice temperature over time, including observations of Titania
at two epochs, and of Ganymede and saturnian ring particles following
emergence from the eclipse shadows of their primary planets.
Finally, we discuss limitations of our temperature measurement method
which can result from the presence of H2O in phases other than hexagonal
ice-I
,
such as amorphous ice, hydrated mineral phases, or
radiation-damaged crystalline ice. Our spectra of Europa and Enceladus
exhibit peculiar spectral features which may result from effects such
as these.
To appear in: Icarus
For preprints, contact grundy@lowell.edu
or on the web at http://www.lowell.edu/users/grundy/public/iceT.html
We describe planetesimal accretion calculations for the dusty
ring observed in the nearby A0 star HR 4796A. Models with
initial masses of 10-20 times the minimum mass solar nebula
produce a ring of width 7-15 AU and height 0.3-0.6 AU at 70 AU
in 
10 Myr. The ring has a radial optical depth
1.
These results agree with limits derived from infrared images and
from the excess infrared luminosity.
To appear in: The Astrophysical Journal
For preprints, contact skenyon@cfa.harvard.edu
or on the web at
http://xxx.lanl.gov/abs/astro-ph/9908125
Triton's Surface Age and Impactor Flux Revisited
S.A. Stern1, & W.B. McKinnon2
1 Department of Space Studies, Southwest Research Institute, #426, 1050
Walnut Street, Boulder, CO 80302, USA
2 Department of Earth and Planetary Sciences and McDonnell Center for the
Space Sciences, Washington University, St. Louis, Missouri, USA
Submitted to: The Astronomical Journal
For preprints, contact alan@boulder.swri.edu
Collision Rates in the Present-day Kuiper Belt and Centaur Regions: Applications to Surface Activation and Modification on Comets, Kuiper Belt Objects, Centaurs, and Pluto-Charon
D. D. Durda1 & S. A. Stern1
1 Department of Space Studies, Southwest Research Institute, #426, 1050 Walnut Street, Boulder, CO 80302, USA
Submitted to: Icarus
For preprints, contact durda@boulder.swri.edu
The American Astronimical Society's 31st Annual Meeting of the Division of
Planetary Science (DPS) meeting will be held October 10-15 in Padova, Italy.
The full list of sessions can be found at:
http://www.aas.org/publications/baas/v31n4/dps99/SL.htm
Below I list some Kuiper Belt-related papers to be presented at the meeting:
Modeling Resonant Structure in the Kuiper Belt
E. K. Holmes, S. F. Dermott, K. Grogan
http://www.aas.org/publications/baas/v31n4/dps99/363.htm
Close Approaches of the trans-Neptunian Objects to Pluto Left Observable Signatures on Their Orbital Distribution
F. Roig, D. Nesvorny, S. Ferraz-Mello
http://www.aas.org/publications/baas/v31n4/dps99/378.htm
The Physical Nature of Centaur Asteroids; Rotation and Colors
N. Peixinho, J.L. Ortiz, P.J. Gutierrez), A. Doressoundiram, M. Roos-Serote
http://www.aas.org/publications/baas/v31n4/dps99/536.htm
1-2.5 Micron Spectra of Centaurs and Trans-Neptunian Objects
S. Kern, D. McCarthy, H. Campins, R.H. Brown, M. Rieke, S. Stolovy
http://www.aas.org/publications/baas/v31n4/dps99/437.htm
Detection of the Kuiper Belt by Stellar Occultation: II
M. Moncuquet, F. Roques
http://www.aas.org/publications/baas/v31n4/dps99/308.htm
Evidence for Early Stellar Encounters in the Orbital Distribution of Edgeworth-Kuiper Belt Objects
S. Ida, J.D. Larwood, A. Burkert
http://www.aas.org/publications/baas/v31n4/dps99/95.htm
Pluto's Family: Might Some Plutinos Be Debris from the Pluto-Charon Binary Formation Event?
S.A. Stern, R.M. Canup, E. Asphaug, D.D. Durda
http://www.aas.org/publications/baas/v31n4/dps99/62.htm
Cratering Rates in the Outer Solar System
K. Zahnle, H. Levison, L. Dones, P. Schenk
http://www.aas.org/publications/baas/v31n4/dps99/541.htm
Separate Spectra of Charon and Pluto from HST/NICMOS
M.W. Buie, W.M. Grundy, S.D. Kern
http://www.aas.org/publications/baas/v31n4/dps99/515.htm
Near-infrared spectral observations of Pluto and Charon
W.M. Grundy, M.W. Buie, S.D. Kern
http://www.aas.org/publications/baas/v31n4/dps99/526.htm
Kuiper Belt Objects
S.C. Tegler, W. Romanishin
http://www.aas.org/publications/baas/v31n4/dps99/244.htm
Stability of Volatiles in the Kuiper Belt and in Extra-Solar Dust Disks
J. Stansberry, R.H. Brown, J. Lunine, D. Trilling, W. Grundy
http://www.aas.org/publications/baas/v31n4/dps99/259.htm
Observations of EKOs and Centaurs: Recoveries, Lightcurves, and Visible-IR Colors
J. Wm. Parker, W. D. Vacca
http://www.aas.org/publications/baas/v31n4/dps99/248.htm
Broad Band Optical Colors of Trans-Neptunian Objects
M.A. Barucci, J. Romon, A. Le Bras, M. Fulchignoni, D. Tholen
http://www.aas.org/publications/baas/v31n4/dps99/162.htm
A Deep Ecliptic Survey with MOSAIC at Kitt Peak National Observatory
R. L. Millis, M. W. Buie, L. H. Wasserman, J. L. Elliot, R. M. Wagner
http://www.aas.org/publications/baas/v31n4/dps99/260.htm
The Scattered Kuiper Belt Objects
C. A. Trujillo, D. C. Jewitt, J. X. Luu
http://www.aas.org/publications/baas/v31n4/dps99/540.htm
Distant TNOs: first results of the ESO survey
A.C. Delsanti, O.R. Hainaut, H. Boehnhardt, C.E. Delahodde, T. Sekiguchi, R.M. West
http://www.aas.org/publications/baas/v31n4/dps99/452.htm
Pioneer 10 Encounter with a Trans-Neptunian Object at 56 AU?
G. Giampieri, J.D. Anderson, E.K. Lau
http://www.aas.org/publications/baas/v31n4/dps99/329.htm
Detection of the Kuiper Belt by Stellar Occultation: I
F. Roques, M. Moncuquet
http://www.aas.org/publications/baas/v31n4/dps99/309.htm
Cometary Activity in TNOs: A Status Report
O.R. Hainaut, C.E. Delahodde, H. Boehnhardt, E. Dotto, M.A. Barucci, K.J. Meech, J. Bauer, R.M West, A. Doressoundiram, G.P. Tozzi
http://www.aas.org/publications/baas/v31n4/dps99/457.htm
Exploration at the Edge of the Solar System: The Pluto-Kuiper Express Mission
R. J. Terrile
http://www.aas.org/publications/baas/v31n4/dps99/417.htm
Pluto, The Edgeworth-Kuiper Belt, and the Pluto-Kuiper Express Flyby Mission
S.A. Stern
http://www.aas.org/publications/baas/v31n4/dps99/54.htm
Uranus and Neptune: Refugees from the Jupiter-Saturn zone?
E. W. Thommes, M. J. Duncan, H. F. Levison
http://www.aas.org/publications/baas/v31n4/dps99/124.htm
The Effects of Gap Formation and Orbital Migration on Planetary Systems
G. Bryden, D. N. C. Lin
http://www.aas.org/publications/baas/v31n4/dps99/579.htm
A decade after the Voyager flyby of Triton and the end of the Pluto/Charon mutual event season, this meeting will provide an opportunity to synthesize recent investigations of this fascinating class of worlds and to explore and compare processes affecting them over time scales ranging from diurnal to cosmological. Themes to be addressed include recent data, interpretations, and models, as well as consideration of what are the most pressing unanswered questions and how they can be resolved through future work.
For more information, visit: http://www.lowell.edu/workshop
There will not be a proceedings volume published from this conference (although abstracts will be available at the website). However, there will be a special Pluto/Triton issue of Icarus. Papers can be submitted by any authors, regardless of whether the attended this workshop or not. Submission deadline is November 15, 1999.
The conference is prompted by the success of the UK Joint Infrastructure Fund bid for VISTA -- the Visible and Infrared Survey Telescope for Astronomy -- a 4-m survey telescope to be constructed in Chile by late 2003.
We are at the beginning of a new era in wide-field astronomy, with major new surveys now in production, and with new telescopes and instruments, both ground- and space-based, scheduled to be in production in the next few years. This conference aims to review the present and future of this exciting new era of wide-field astronomy, and to discuss the optimum exploitation of the remarkable range of new facilities.
The conference will cover all aspects of the new era -- cosmology and both extragalactic and galactic astronomy, from X-ray to radio. Themes include the following:
For more information and preliminary registration visit the conference web site
at
http://www.uclan.ac.uk/new_era
CONTACT:
Centre for Astrophysics
Attn: Dr R.G. Clowes
University of Central Lancashire
Preston
PR1 2HE
United Kingdom
Phone: +44 (0) 1772 893540
Fax: +44 (0) 1772 892996
E-mail: r.g.clowes@uclan.ac.uk
The AAS Job Register (http://www.aas.org/JobRegister/aasjobs.html) has the most complete and up-to-date listing of astronomy jobs. Here are a selected few jobs I gleaned from the list that may be of interest to Kuiper belt scientists. For brevity, I have omitted the job descriptions, but you can follow the links given below, or from the Distant EKOs job page at http://www.boulder.swri.edu/ekonews/jobs.html.
Lowell Postdoctoral Fellowship
Lowell Observatory, Flagstaff, Arizona, USA
http://www.lowell.edu/misc/post_doc.html
Planetary Science Faculty Position
Massachusettes Institute of Technology, Cambridge, Massachusettes, USA
http://www.aas.org/JobRegister/no10696.html
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.