We present a deep optical survey of Uranus's Hill sphere for small satellites. The 8 m Subaru Telescope was used to survey about 3.5 square degrees with a 50% detection efficiency at limiting red magnitude m(R) = 26.1. This magnitude corresponds to objects that are about 7 km in radius (assuming an albedo of 0.04). We detected ( without prior knowledge of their positions) all previously known outer satellites and discovered two new irregular satellites (S/2001 U2 and S/2003 U3). The two inner satellites Titania and Oberon were also detected. One of the newly discovered bodies (S/2003 U3) is the first known irregular prograde satellite of the planet. The population, size distribution, and orbital parameters of Uranus's irregular satellites are remarkably similar to those of the irregular satellites of gas giant Jupiter. Both have shallow size distributions (power-law indices q similar to 2 for radii larger than 7 km) with no correlation between the sizes of the satellites and their orbital parameters. However, unlike those of Jupiter, Uranus's irregular satellites do not appear to occupy tight, distinct dynamical groups in semimajor-axis versus inclination phase space. Two groupings in semimajor-axis versus eccentricity phase space appear to be statistically significant.

A detailed description of the Halley-type Comet C/2001 OG(108) (LONEOS) has been derived from visible, near-infrared, and mid-infrared observations obtained in October and November 2001. These data represent the first high-quality ground-based observations of a bare Halley-type comet nucleus and provide the best characterization of a Halley-type comet other than 1P/Halley itself. Analysis of time series photometry suggests that the nucleus has a rotation period of 57.2 +/- 0.5 h with a minimum nuclear axial ratio of 1.3, a phase-darkening slope parameter G of -0.01 +/- 0.10, and an estimated H = 13.05 +/- 0.10. The rotation period of C/2001 OG(108) is one of the longest observed among comet nuclei. The V-R color index for this object is measured to be 0.461 +/- 0.02, which is virtually identical to that of other cometary nuclei and other possible extinct comet candidates. Measurements of the comet's thermal emission constrain the projected elliptical nuclear radii to be 9.6 +/- 1.0 km and 7.4 +/- 1.0 km, which makes C/2001 OG(108) one of the larger cometary nuclei known. The derived geometric albedo in V-band of 0.040 +/- 0.010 is typical for comet nuclei. Visible-wavelength spectrophotometry and near-infrared spectroscopy were combined to derive the nucleus's reflectance spectrum over a 0.4 to 2.5 mu m wavelength range. These measurements represent one of the few nuclear spectra ever observed and the only known spectrum of a Halley-type comet. The spectrum of this comet nucleus is very nearly linear and shows no discernable absorption features at a 5% detection limit. The lack of any features, especially in the 0.8 to 1.0 mu m range such as are seen in the spectra of carbonaceous chondrite meteorites and many low-albedo asteroids, is consistent with the presence of anhydrous rather than hydrous silicates on the surface of this comet. None of the currently recognized meteorites in the terrestrial collections have reflectance spectra that match C/2001 OG(108). The near-infrared spectrum, the geometric albedo, and the visible spectrophotometry all indicate that C/2001 OG(108) has spectral properties analogous to the D-type, and possibly P-type asteroids. Comparison of the measured albedo and diameter of C/2001 OG(108) with those of Damocloid asteroids reveals similarities between these asteroids and this comet nucleus, a finding which supports previous dynamical arguments that Damocloid asteroids could be composed of cometary-like materials. These observations are also consistent with findings that two Jupiter-family comets may have spectral signatures indicative of D-type asteroids. C/2001 OG(108) probably represents the transition from a typical active comet to an extinct cometary nucleus, and, as a Halley-type comet, suggests that some comets originating in the Oort cloud can become extinct without disintegrating. As a near-Earth object, C/2001 OG(108) supports the suggestion that some fraction of the near-Earth asteroid population consists of extinct cometary nuclei. (c) 2005 Elsevier Inc. All rights reserved.

The dynamical and physical characteristics of asteroids, comets, Kuiper Belt objects and satellites give us insight on the processes operating in the Solar System and allow us to probe the planet formation epoch. The recent advent of sensitive, wide-field CCD detectors are allowing us to complete the inventory of our Solar System and obtain detailed knowledge about the small bodies it contains. I will discuss the recent results with a focus on the new bodies being discovered beyond Neptune with a particular emphasis on the very distant orbit of (90377) Sedna and 2003 UB313, which is larger than Pluto.

We surveyed 1.75 deg(2) of sky near Neptune to an R-band 50% detection efficiency of 25.8 mag (corresponding to radii of about 17 km for an assumed albedo of 0.04). We discovered one new outer satellite, Psamathe (S/2003 N1), about 20 km in radius with a distant retrograde orbit and moderate eccentricity. Until 2003 Neptune was only known to have two satellites that exhibited orbital signatures indicative of capture. Both of these, Triton and Nereid, are unusual when compared to the irregular satellites of other giant planets. With recent discoveries of four additional satellites by Holman et al. it is now apparent that Neptune has a distant "normal'' irregular satellite system in which the satellites have radii and orbital properties similar to those of the satellites of other giant planets. We find that the satellite size distribution at Neptune is not well determined given the few objects known to date, being especially sensitive to the inclusion of Triton and Nereid in the sample. Finally, we note that Psamathe and S/2002 N4 have similar semimajor axes, inclinations, and eccentricities. They may be fragments of a once-larger satellite.

The dynamical and physical properties of asteroids offer one of the few constraints on the formation, evolution, and migration of the giant planets. Trojan asteroids share a planet's semimajor axis but lead or follow it by about 60 degrees near the two triangular Lagrangian points of gravitational equilibrium. Here we report the discovery of a high-inclination Neptune Trojan, 2005 TN53. This discovery demonstrates that the Neptune Trojan population occupies a thick disk, which is indicative of "freeze-in'' capture instead of in situ or collisional formation. The Neptune Trojans appear to have a population that is several times larger than the Jupiter Trojans. Our color measurements show that Neptune Trojans have statistically indistinguishable slightly red colors, which suggests that they had a common formation and evolutionary history and are distinct from the classical Kuiper Belt objects.

The redshift distribution of the short-duration gamma-ray bursts (GRBs) is a crucial, but currently fragmentary, clue to the nature of their progenitors. Her ewe present optical observations of nine short GRBs obtained with Gemini, Magellan, and the Hubble Space Telescope. We detect the afterglows and host galaxies of two short bursts, and host galaxies for two additional bursts with known optical afterglow positions, and five with X-ray positions (less than or similar to 6 '' radius). In eight of the nine cases we find that the most probable host galaxies are faint, R approximate to 23-26.5 mag, and are therefore starkly different from the first few short GRB hosts with R approximate to 17-22 mag and z less than or similar to 0.5. Indeed, we measure spectroscopic redshifts of z approximate to 0.4-1.1 for the four brightest hosts. A comparison to large field galaxy samples, as well as the hosts of long GRBs and previous short GRBs, indicates that the fainter hosts likely reside at z greater than or similar to 1. Our most conservative limit is that at least half of the five hosts without a known redshift reside at z > 0.7 (97% confidence level), suggesting that about 1/3 to 2/3 of all short GRBs originate at higher redshifts than previously determined. This has two important implications: (1) we constrain the acceptable age distributions to a wide lognormal (sigma greater than or similar to 1) with tau(*)similar to 4-8 Gyr, or to a power law, P(tau) proportional to tau(n), with -1 less than or similar to n less than or similar to 0; and ( 2) the inferred isotropic energies, E-gamma,E-iso similar to 10(50)-10(52) ergs, are significantly larger than similar to 10(48)-10(49) ergs for the low-redshift, short GRBs, indicating a large spread in energy release or jet opening angles. Finally, we reiterate the importance of short GRBs as potential gravitational-wave sources and find a conservative detection rate with the advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) of similar to 2-6 yr(-1).

I report new time-resolved light curves and determine the rotations and phase functions of several large Kuiper Belt objects, which includes the dwarf planet Eris (2003 UB313). Three of the new sample of 10 trans-Neptunian objects display obvious short-term periodic light curves. (120348) 2004 TY364 shows a light curve which if double-peaked has a period of 11.70 +/- 0.01 hr and a peak-to-peak amplitude of 0.22 +/- 0.02 mag. (84922) 2003 VS) has a well-defined double-peaked light curve of 7.41 +/- 0.02 hr with a range of 0.21 +/- 0.02 snag. (126154) 2001 YH 140 shows variability of 0.21 +/- 0.04 snag with a possible 13.25 +/- 0.2 hr single-peaked period. The seven new Kuiper Belt objects in the sample which show no discernible variations within the uncertainties on short rotational timescales are (148780) 2001 UQ(18), (55565) 2002 AW (197), (119979) 2002 WC19, (120132) 2003 FY128, (136108) Eris 2003 UB313, (90482) Orcus 2004 DW, and (90568) 2004 GV(9). Four of the 10 newly sampled Kuiper Belt objects were observed over a significant range of phase angles to determine their phase functions and absolute magnitudes. The three medium- to large-sized Kuiper Belt objects 2004 TY364, Orcus, and 2004 GV9 show fairly steep linear phase curves (similar to 0.18 to 0.26 snag deg(-1)) between phase angles of 0.1 degrees and 1.5 degrees. This is consistent with previous measurements obtained for moderately sized Kuiper Belt objects. The extremely large dwarf planet Eris (2003 UB 313) shows a shallower phase curve (0.09 +/- 0.03 mag deg-1) which is more similar to the other known dwarf planet Pluto. It appears that the surface properties of the largest dwarf planets in the Kuiper Belt may be different than the smaller Kuiper Belt objects. This may have to do with the larger objects' ability to hold more volatile ices as well as sustain atmospheres. Finally, it is found that the absolute magnitudes obtained using the phase slopes found for individual objects are a few tenths of magnitudes different than that given by the Minor Planet Center.

A search of the Two Micron All Sky Survey (2MASS) and Sloan Digital Sky Survey (SDSS) reveals 36 previously unknown high proper motion objects with J < 17 mag. Their red optical colors indicate that 27 are M dwarfs, eight are early-type L dwarfs, and one is a late-type T dwarf. The L dwarfs have J - K-s colors near the extrema of known L dwarfs, indicating that previous surveys for L dwarfs using color as a selection criterion may be biased. Follow-up near-infrared spectroscopy of six dwarfs confirm that they are all late-type with spectral types ranging from M8 to T4. Spectroscopy also shows that some of the L dwarf spectra exhibit peculiar features similar to other peculiar "blue" L dwarfs, which may indicate that these dwarfs have a relatively condensate free atmosphere or may be metal poor. Photometric distance estimates indicate that 22 of the new M, L, and T dwarfs lie within 100 pc of the Sun with the newly discovered T dwarf, 2MASS J10595185+3042059, located at similar to 25 pc. Based on the colors and proper motions of the newly identified objects, several appear to be good subdwarf candidates. The proper motions of known ultracool dwarfs detected in our survey were also measured, including, for the first time, SDSS J085834.42+325627.6 (T1), SDSS J125011.65+392553.9 (T4), and 2MASS J15261405+2043414 (L7).

We present observations of thermal emission from fifteen transneptunian objects (TNOs) made using the Spitzer-Space Telescope. Thirteen of the targets are members of the Classical Population: six dynamically hot Classicals, five dynamically cold Classicals, and two dynamically cold inner Classical Kuiper belt objects (KBOs). We fit out observations using thermal models to determine the sizes and albedos Of Our targets finding that the cold Classical KBOs have distinctly higher Visual albedos than the hot Classicals and other TNO dynamical classes. The cold Classicals Ire known to be distinct from other TNOs in terms of their Color distribution, size distribution, and binarity fraction. The Classical objects in our sample all have Fed colors yet they show a diversity of albedos which suggests that there is not a simple relationship between albedo and color. As a consequence of high albedos, the mass estimate of the cold Classical Kuiper belt is reduced from approximately 0.01 M-circle plus to approximately 0.001 M-circle plus. Our results also increase significantly the sample of small Classical KBOs with known albedos and sizes from 21 to 32 Such objects. (c) 2009 Elsevier Inc. All rights reserved,