MPEC H21 announced the discovery of a Neptunian trojan (1:1 resonannce) by Sheppard, Trujillo, and Jewitt. The object 2004 UP10 is the second known Neptunian trojan (2001 QR322 being the first).
The ``Cold Classical'' Kuiper Belt is the only part of the Kuiper Belt where objects show distinct color statistics from the rest of the transneptunian population. Cold Classical orbits are also likely to have been among the least dynamically perturbed since the time of accretion. As such, Cold Classical objects are especially interesting targets for compositional investigation by means of near-infrared spectroscopy. In this paper we report the first published infrared spectrum of a likely member of this unique class of objects. A 1.4 to 2.5 m spectrum of the Cold Classical candidate object (79360) 1997 CS29 obtained at Keck 1 is spectrally featureless.
We present low resolution K band spectra taken at the Gemini 8 meter telescope of (90377) Sedna and (90482) Orcus (provisional designations 2003 VB12 and 2004 DW, respectively), currently the two minor planets with the greatest absolute magnitudes (i.e. the two most reflective minor planets). We place crude limits on the surface composition of these two bodies using a Hapke model for a wide variety of assumed albedos. The unusual minor planet (90377) Sedna was discovered on November 14, 2003 UT at roughly 90 AU with 1.6 times the heliocentric distance and perihelion distance of any other bound minor planet. It is the first solar system object discovered between the Kuiper Belt and the Oort Cloud, and may represent a transition population between the two. The reflectance spectrum of (90377) Sedna appears largely featureless at the current signal-to-noise ratio, suggesting a surface likely to be highly processed by cosmic rays. For large grain models (100 micron to 1 cm) we find that (90377) Sedna cannot have more than 70% surface fraction of water ice or more than 60% surface fraction of methane ice to confidence. Minor planet (90482) Orcus shows strong water ice absorption corresponding to less than 50% surface fraction for grain models 25 micron and larger. Orcus cannot have more than 30% of its surface covered by large (100 mm to 1 cm) methane grains to confidence.
In April 2004, we obtained visible and near-infrared spectroscopy and photometry of the Transneptunian Object (TNO) 90482 Orcus (2004 DW) with the European Southern Observatory (ESO) 8-m telescopes of the Very Large Telescope (VLT) in Chile. This object, discovered on February 17, 2004, is one of the largest known TNOs, and it belongs to the dynamical class of Plutinos. The high signal-to-noise ratio visible spectrum recorded on April 11, 2004, is nearly flat, in good agreement with the BVRI photometry we obtained the same night and with photometric measurements from Rabinowitz et al. (2004). The near-infrared spectra (J, H, and K bands) were obtained on April 11, 12, and 21, 2004. Relatively strong absorptions attributed to water ice were detected around 1.5 and 2 microns. We compare these data with spectra of Orcus obtained at the 3.56-m Telescopio Nazionale Galileo (TNG) by Fornasier et al. (2004a). Only two of the TNOs observed so far exhibit stronger water ice absorptions in their spectra than Orcus. Attempts to model the entire visible-near infrared spectrum yield tentative fits with mixtures of water ice and carbonaceous compounds.
Trans-Neptunian Objects (TNOs) and Centaurs display the widest color diversity in comparison to other small Solar system bodies. The investigation of their properties can help in understanding the evolution of these objects. In this paper we propose a classification scheme based on multivariable statistical analysis of a homogeneous, high quality set of B-V, V-R, V-I and V-J colors indices. Analyzing a sample of 51 objects and using a high confidence level, four groups have been identified and named : BB, BR, IR and RR. The group BB contains objects with neutral color, RR those with very red color, while the others have intermediate behavior. We extended the analysis of other 84 objects for which three colors are available obtaining a preliminary classification. A tentative interpretation of these groups in terms of surface characteristics is given.
The New Horizons 2 (NH2) Uranus-KB mission plans for a new science team, selected competitively by NASA. A workshop will be held from 7:00-9:00 pm on Wednesday, June 8th, which is the evening before the Boulder OPAG (Outer Planets Assessment Group) meeting. The goals of the NH2 workshop will be to ask for input to NH2 mission objectives, present the results of the NH2 study done this spring by NASA, and solicit desirable science team attributes for NH2.
The workshop will be held at the Southwest Research Institute's Department of Space Studies, located at 1050 Walnut Street, Suite 400. This is just 4 blocks from OPAG's Boulderado hotel site; see http://www.boulder.swri.edu/officeinfo.html for maps. Food and drinks will be provided.
Interested participants should contact Carrie Chavez at cchavez@mail.arc.nasa.gov to register.