In the ``reports of my death have been greatly exaggerated'' category, the
canceled Pluto/Kuiper Express mission has been resurrected. The Announcement
of Opportunity for the restructured Pluto-Kuiper Belt Mission is at:
http://spacescience.nasa.gov/ao/01-oss-01/draft/.
One of the recently-discovered TNOs, 2000 WR106, got a fair amount of popular
press (e.g.,
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1054000/1054157.stm)
since it is apparently quite large. As reported on January 2nd in IAUC 7554,
Jewitt and Aussel used submillimeter observations to estimate a diameter of
900 km, roughly the size of Charon and Ceres
,
making 2000 WR106 the
largest TNO discovered to date (other than Charon's companion...).
2000 WR106 was also detected during a few earlier epochs on Palomar digitized
sky survey images (MPEC 2000-Y45;
http://cfa-www.harvard.edu/mpec/K00/K00Y45.html), and it now has a
baseline of astrometry measurements back to 1954. This gives it the claim to
another superlative as the object that has gone from discovery to being
eligible for numbering in the shortest amount of time, about one month. The
measurements from those earlier epochs establish that 2000 WR106 is a
``classical'' TNO (cubewano); the recent observations alone would not have been
able to rule out a highly eccentric (scattered disk) orbit.
Rather appropriate since January 1st was the bicentennial
anniversary of the discovery of Ceres.
The discovery rate continues to climb, with 146 objects discovered in 1999 and 158 objects discovered in 2000 (and a few more reports of discoveries likely to trickle in over the next month or so).
There were 38 new TNO discoveries announced since the previous issue of the Distant EKOs Newsletter:
2000 SB331, 2000 SC331, 2000 SD331, 2000 SE331, 2000 SF331, 2000 SG331, 2000 SH331, 2000 SJ331, 2000 SK331, 2000 SL331, 2000 SO331, 2000 SP331, 2000 ST331, 2000 WK183, 2000 WL183, 2000 WM183, 2000 WN183, 2000 WO183, 2000 WR106, 2000 WT169, 2000 WV12, 2000 WW12, 2000 WX12, 2000 YA2, 2000 YB2, 2000 YC2, 2000 YD2, 2000 YE2, 2000 YF2, 2000 YG2, 2000 YH2, 2000 YU1, 2000 YV1, 2000 YW1, 2000 YX1, 2000 YY1, 2000 YZ1, 2000 YB29
and 8 new Centaur/SDO discoveries:
2000 SN331, 2000 SM331, 2000 SQ331, 2000 SR331, 2000 SS331, 2000 SU331, 1996 AR20, 1996 AS20
Reclassified objects:
2000 CQ105 (TNO
SDO)
Objects with new designations:
1994 VK8 (19255)
1996 SZ4 (19299)
1996 TO66 (19308)
1998 WH24 (19521)
Current number of TNOs: 366 (and Pluto & Charon)
Current number of Centaurs/SDOs: 64
I had sent out a message asking if people still wanted the LaTeX file for each
issue of the Newsletter, or if just a notice with a table of contents and a web
address would be sufficient. Since a surprising number of people requested
that I still send out the full LaTeX file, I will continue to do so (the
pro-LaTeX faction beat out con-LaTeX faction by two votes, but the majority of
votes didn't have a strong preference one way or the other; no hanging chads,
no recount). However, for those of you who don't use the LaTeX file, note that
the header of the file contains an ASCII version of the issue's table of
contents and the web address showing the location of the HTML, PS, and PDF
versions of the new issue (which can always be found at http://www.boulder.swri.edu/ekonews/issues/).
In the future, if Distant EKOs begins to publish larger files (e.g.,
figures) that would be more cumbersome to include via e-mail, it may become
completely web-based with just an e-mail reminder when each issue becomes
available.
-jp-
We investigate the constraints that Olbers Paradox, applied to the
Zodiacal Background as measured from space, sets on outer solar system
objects. If extended to very faint limits, 
40-50 mag, the
steep optical number counts of Kuiper Belt objects (KBOs) at
26 imply an infinitely bright night sky. Small KBOs with
radii of 
1 
m to
1 km must have a size distribution
r-a, with 
3.4 or smaller to satisfy the
known limits on the sky-surface brightness at optical and far-infrared
wavelengths. Improved limits on the measured KBO surface brightness
can yield direct estimates of the albedo, temperature, and size
distribution for small KBOs in the outer solar system.
To appear in: The Astrophysical Journal Letters (10 January 2001)
Preprints available on the web at http://cfa-www.harvard.edu/~kenyon/preprints.html
We investigate the dynamical evolution of 210 hypothetical massless bodies initially situated between 10 and 30 AU from the Sun in order to determine the general characteristics of the evolved system. This is of particular relevance to the understanding of the origin of Edgeworth-Kuiper belt objects on scattered intermediate orbits, such as 1996 TL66, which have high eccentricity and semimajor axis but nevertheless have perihelion in the region between 30 and 50 AU from the Sun.
Published in: Monthly Notices of the Royal Astronomical Society, 318, 482
For preprints, contact i.p.williams@qmw.ac.uk
The stability of the 2:3 mean motion resonance with Neptune is systematically explored and compared to the observed resonant population. It is shown that orbits with small and moderate amplitudes of the resonant angle are stable over the age of the Solar System. The observed resonant population is distributed within the stability limits. There exists an interval of large resonant amplitudes, where orbits are marginally unstable. Resonant objects starting in this interval may leave the resonance by slow increase of their resonant amplitudes on a time scale of several billion years. These objects eventually attain Neptune-crossing trajectories and contribute to the flux of Jupiter-family comets. The number of objects leaking from the 2:3 resonance per time interval is calibrated by the number of objects needed to keep the Jupiter-family comets population in steady state. This allows us to compute the upper limit of the number of resonant objects with cometary size. The effects of collisions and mutual gravitational scattering are discussed in this context.
Published in: Icarus, 148, 282 (2000 November)
For preprints, contact david@obs-nice.fr, froig@iagusp.usp.br
The stability of orbits in the trans-Neptunian region is numerically computed. It is found that, in analogy to the asteroid belt, there exist many chaotic layers at places of thin mean motion resonances. These are either moderate- and high-order resonances with Neptune or three-body resonances with Neptune and Uranus. The orbital eccentricity chaotically increases at the thin resonances allowing some Kuiper Belt Objects (KBOs) to be slowly transferred to Neptune-crossing orbits. The stability of two large mean motion resonances with Neptune -- 1:2 and 3:4 -- is systematically explored. It is shown that in both resonances, the orbits with small resonant amplitudes are stable over the age of the Solar System. The possible role of collisions and dynamical scattering in clearing the resonances is discussed. It is inferred from orbital angles of 1997 SZ10 and 1996 TR66 that these bodies are most probably on tadpole orbits in the 1:2 Neptune resonance.
To appear in: Icarus
For preprints, contact david@obs-nice.fr, froig@iagusp.usp.br
Kuiper belt objects (KBOs) are an ancient reservoir of comets beyond Neptune's
orbit. Some of these objects were recently found to have the reddest optical
colours in the Solar System, but the number of objects for which accurate
colours were available was too small for any correlation to be discerned
between colour and physical or dynamical properties, which might shed light on
the origin of these objects. Here we report that all nine of the KBOs in our
survey on near-circular (low eccentricity) orbits with perihelion distances
larger than 40 AU have extremely red surfaces, thereby connecting an observable
property with a dynamical class. Of the objects with orbital eccentricities
greater than 0.1, about half are also very red, while the rest have colours
similar to the Sun, meaning that reflected sunlight is not strongly modified
by the objects' surface properties. In addition, of the 13 `classical' KBOs
(those with semi-major axes a 
AU and eccentricity e < 0.15), the
ten that are very red are in orbits with small angles of inclination to the
ecliptic, whereas the three with solar colours are all in high-inclination
orbits. We suggest that these three `grey' classical KBOs may be part of a
dynamical group that is separate from the `red' classical KBOs.
Published in: Nature, 407, 979 (2000 October 26)
For reprints, contact Stephen.Tegler@nau.edu
We present a new analysis of the currently available orbital elements
for the known Kuiper belt objects. In the non-resonant, main Kuiper
belt we find a statistically significant relationship between an
object's absolute magnitude (H) and its inclination (i). Objects
with H<6.5 (i.e. radii
km for a 4% albedo) have
higher inclinations than those with H>6.5 (radii
km). We have shown that this relationship is not caused by any
obvious observational bias. We argue that the main Kuiper belt
consists of the superposition of two distinct distributions. One is
dynamically hot with inclinations as large as
and
absolute magnitudes as bright as 4.5; the other is dynamically cold
with
and H>6.5. The dynamically cold population
is most likely dynamically primordial. We speculate on the potential
causes of this relationship.
To appear in: The Astronomical Journal
For preprints, contact hal@gort.boulder.swri.edu
or on the web at http://www.boulder.swri.edu/~hal/papers.html
Using the observed properties of our solar system, in particular
the isotopic compositions of meteorites and the regularity of the
planetary orbits, we constrain the star formation environment of the
Sun within the scenario of (external) radioactive enrichment by a
massive star. This calculation yields a probability distribution for
the number of stars in the solar birth aggregate. The Sun is most
likely to have formed within a stellar group containing
1100 members. The a priori
probability of a star forming in this type of environment is
0.0085, i.e., only about 1 out of 120 solar systems are
expected to form under similar conditions. We discuss additional
implications of this scenario, including possible effects from the
radiation fields provided by the putative cluster environment and
dynamical disruption of the Kuiper Belt. The constraints of this paper
place tight restrictions on the properties of the solar birth
aggregate for the scenario of external enrichment by a massive star;
alternately, these tight constraints slightly favor a self-enrichment
scenario for the short-lived radioactive species.
To appear in: Icarus
For preprints, contact fca@umich.edu
or on the web at http://www.arXiv.org/abs/astro-ph/0011326
The Rotation Axis of the Centaur 5145 Pholus
Tony L. Farnham1
1 University of Texas, Department of Astronomy, Austin, TX 78712, USA
Submitted to: Icarus
For preprints, contact farnham@zinfandel.as.utexas.edu
Upper Limits on Gaseous CO at Pluto and Triton from High-Resolution Near-IR Spectroscopy
L.A. Young1, J.C. Cook2, R.V. Yelle3, and E.F. Young1
1 Southwest Research Institute,
1050 Walnut Street, Suite 426, Boulder CO 80302, USA
2 Arizona State University,
Department of Physics and Astronomy, Tempe AZ 85287, USA
3 Northern Arizona University, Physics and Astronomy Department,
Flagstaff, AZ 86011, USA
Submitted to: Icarus
For preprints, contact layoung@boulder.swri.edu
or on the web at
http://www.boulder.swri.edu/~layoung/eprint/COupperlim/
UV Observations of Triton in 1999 with HST/STIS:
2150-3180 Å Spectroscopy and Disk-Integrated Photometry
L.A. Young1 and S.A. Stern1
1 Southwest Research Institute, 1050 Walnut Stree, Suite 426, Boulder, CO 80302, USA
Submitted to: The Astronomical Journal
For preprints, contact layoung@boulder.swri.edu
or on the web at
http://www.boulder.swri.edu/~layoung/eprint/TritonSTIS_99/
The Lightcurve and Colors of Unusual Minor Planet 1998 WU24
John K. Davies1, David J. Tholen2, Robert J. Whiteley2, Simon F. Green3, Jon K. Hillier4, Michael J. Foster4, Neil McBride3, Tom. H Kerr1, and Erica Muzzerall1
1 Joint Astronomy Centre, 660 N A'ohoku Pl., Hilo, Hawaii, 96720, USA
2 Institute for Astronomy, 2680 Woodlawn Dr, Honolulu, Hawaii, 96822, USA
3 Planetary and Space Science Research Institute, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
4 Unit for Space Sciences & Astrophysics, University of Kent, Canterbury, CT2 7NR, UK
To appear in: Icarus
For preprints, contact j.davies@jach.hawaii.edu
or on the web linked from http://www.jach.hawaii.edu/~jkd/cv.html
National Central University is undertaking an EKO occultation survey program, in collaboration with Lawrence Livermore National Laboratory (USA), Academia Sinica (Taiwan), and other institutes. The Taiwan-America Occultation Survey (TAOS) aims to set up an array of small telescopes in Taiwan to monitor chance stellar occultation events by EKOs. Applications are invited for a postdoc position to work on this project. The successful applicant shall work in Taiwan, to spend half of the time on his/her own research, and the other half helping out hardware and software development, data analysis, and scientific interpretation specifically to this project. Application should include a CV with publication list, a statement for research plan, and three names from whom reference letters can be request. Applications received by 31 January 2001 will receive full consideration. Inquires and applications should sent to:
Prof W. P. Chen
Institute of Astronomy
National Central University
Chung-Li 32054, TaiwanTelephone: +886-3-422-3424
Fax: +886-3-426-2304
wchen@astro.ncu.edu.tw
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.