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).

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,

We present a systematic survey for satellites of Venus using the Baade-Magellan 6.5 m telescope and IMACS wide-field CCD imager at Las Campanas observatory in Chile. In the outer portions of the Hill sphere the search was sensitive to a limiting red magnitude of about 20.4, which corresponds to satellites with radii of a few hundred meters when assuming an albedo of 0.1. In the very inner portions of the Hill sphere scattered light from Venus limited the detection to satellites of about a kilometer or larger. Although several main belt asteroids were found, no satellites (moons) of Venus were detected. (C) 2009 Elsevier Inc. All rights reserved.

The Kuiper belt is a collection of small bodies (Kuiper belt objects, KBOs) that lie beyond the orbit of Neptune and which are believed to have formed contemporaneously with the planets. Their small size and great distance make them difficult to study. KBO 55636 (2002 TX300) is a member of the water-ice-rich Haumea KBO collisional family(1). The Haumea family are among the most highly reflective objects in the Solar System. Dynamical calculations indicate that the collision that created KBO 55636 occurred at least 1 Gyr ago(2,3). Here we report observations of a multi-chord stellar occultation by KBO 55636, which occurred on 9 October 2009 UT. We find that it has a mean radius of 143 +/- 65 km (assuming a circular solution). Allowing for possible elliptical shapes, we find a geometric albedo of 0.88(0.06)(+0.15) in the V photometric band, which establishes that KBO 55636 is smaller than previously thought and that, like its parent body, it is highly reflective. The dynamical age implies either that KBO 55636 has an active resurfacing mechanism, or that fresh water-ice in the outer Solar System can persist for gigayear timescales.

The structural behavior of Al3+ in peralkaline glasses and melts along the Na2Si3O7-Na-2(NaAl)(3)O-7 join has been examined to 1200degreesC at ambient pressure with Si-29 MAS NMR and Raman spectroscopy. The distribution of Al3+ among coexisting Q(4), Q(3), and Q(2) structural units in the glasses and melts was determined as a function of bulk Al/(Al+Si) and temperature. The Al3+ resides principally in Q(4) structural units, which contain more than 70% of the total amount of Al3+. The Q(2) units contain the smallest amount of Al3+ among the Q(4), Q(3), and Q(2) structural units. There is no evidence for temperature-dependent distribution of Al3+ among the coexisting structural units at least to 1100-1200degreesC.

Cation ordering in covalent oxide glasses and melts profoundly affects the macroscopic properties, such as viscosity, diffusivity, and thermodynamic potentials. It is commonly assumed that in glasses and melts nonframework cations such as Na+, Ca2+, and Ba2+ distribute randomly around nonbridging oxygen (NBO). Several macroscopic studies on the melting of silicates and thermodynamic data have suggested that a possible nonrandomness may exist among cations around NBO in mixed-cation silicate glasses. Here, we report unambiguous experimental evidence of chemical ordering of nonframework cations and demonstrate a clear preference for certain types of cation-NBO complexes in mixed-cation silicate glasses using O-17 magic angle spinning (MAS) and multiple quantum MAS NMR. Particularly, complete bonding preference and cation ordering occurs in Ba-Mg silicate glasses (BaMgSi2O6) glass in such a way that nonbridging oxygen either only has Ba2+ as a nearest neighbor (Ba-NBO) or exists as a complex containing one Ba+ and two Mg2+ as nearest neighbors while no detectable fraction of Mg-NBO is observed. Ba-Na silicate glasses, on the other hand, show a wide distribution of configurations for two types of cations around NBO, forming Ba- and Na-NBO as well as substantial intensity of mixed NBO peaks, which indicates a prevalence of dissimilar pairs around NBO or a stronger preference to Ba-O-Si-[4] over Na-O-Si-[4]. The present results, combined with the previous results on Na-Ca silicate glasses, highlight the tendency for chemical ordering upon cation mixing in oxide glasses and may provide an atomistic explanation for diffusivity anomalies as well as activity-composition relationship of silicate melts.