We present optical V band albedo distributions for middle solar system minor bodies including Centaurs, Jovian Trojans, and Hildas. Diameters come mostly from the NEOWISE catalog. Optical photometry ...(H values) for about two-thirds of the ∼2700 objects studied are from Pan-STARRS, supplemented by H values from JPL Horizons (corrected to the Pan-STARRS photometric system). Optical data for Centaurs are from our previously published work. The albedos presented here should be superior to previous work because of the use of the Pan-STARRS optical data, which is a homogeneous data set that has been transformed to standard V magnitudes. We compare the albedo distributions of pairs of samples using the nonparametric Wilcoxon test. We strengthen our previous findings that gray Centaurs have lower albedos than red Centaurs. The gray Centaurs have albedos that are not significantly different from those of the Trojans, suggesting a common origin for Trojans and gray Centaurs. The Trojan L4 and L5 clouds have median albedos that differ by ∼10% at a very high level of statistical significance, but the modes of their albedo distributions differ by only ∼1%. We suggest the presence of a common "true background" in the two clouds, with an additional more reflective component in the L4 cloud. We find, in agreement with Grav et al. that the Hildas are darker than the Trojans by 15%-25%. Perhaps the Hildas are darker because of their passage near perihelion through zone III of the main asteroid belt, which might result in significant darkening by gardening.
ABSTRACT We present new optical colors for 28 Kuiper Belt objects (KBOs) and 35 Centaur objects measured with the 1.8 m Vatican Advanced Technology Telescope and the 4.3 m Discovery Channel ...Telescope. By combining these new colors with our previously published colors, we increase the sample size of our survey to 154 objects. Our survey is unique in that the uncertainties in our color measurements are less than half the uncertainties in the color measurements reported by other researchers in the literature. Small uncertainties are essential for discerning between a unimodal and a bimodal distribution of colors for these objects as well as detecting correlations between colors and orbital elements. From our survey, it appears red Centaurs have a broader color distribution than gray Centaurs. We find red Centaurs have a smaller orbital inclination angle distribution than gray Centaurs at the 99.3% confidence level. Furthermore, we find that our entire sample of KBOs and Centaurs exhibits bimodal colors at the confidence level. KBOs and Centaurs with HV > 7.0 have bimodal colors at the 99.96% confidence level and KBOs with HV < 6.0 have bimodal colors at the 96% confidence level.
In 2007, the M-type binary Asteroid 22 Kalliope reached one of its annual equinoxes. As a consequence, the orbit plane of its small moon, Linus, was aligned closely to the Sun's line of sight, giving ...rise to a mutual eclipse season. A dedicated international campaign of photometric observations, based on amateur–professional collaboration, was organized and coordinated by the IMCCE in order to catch several of these events. The set of the compiled observations is released in this work. We developed a relevant model of these events, including a topographic shape model of Kalliope refined in the present work, the orbit solution of Linus as well as the photometric effect of the shadow of one component falling on the other. By fitting this model to the only two full recorded events, we derived a new estimation of the equivalent diameter of Kalliope of
166.2
±
2.8
km
, 8% smaller than its IRAS diameter. As to the diameter of Linus, considered as purely spherical, it is estimated to
28
±
2
km
. This substantial “shortening” of Kalliope, gives a bulk density of
3.35
±
0.33
g
/
cm
3
, significantly higher than past determinations but more consistent with its taxonomic type. Some constraints can be inferred on the composition.
We present three near-infrared spectra of Pluto taken with the Infrared Telescope Facility and SpeX, an optical spectrum of Triton taken with the MMT and the Red Channel Spectrograph, and previously ...published spectra of Pluto, Triton, and Eris. Specifically, we measure the methane-nitrogen mixing ratio across and into the surfaces of these icy dwarf planets. In addition, we present a laboratory experiment that demonstrates it is essential to model methane bands in spectra of icy dwarf planets with two methane phases-one highly diluted by nitrogen and the other rich in methane. Application of the Wilcoxon rank sum test to our measurements finds these small differences are statistically significant. This result is contrary to the expectation that since visible light penetrates deeper into a nitrogen-rich surface than the depths from which thermal emission emerges, net radiative heating at depth would drive preferential sublimation of nitrogen leading to an increase in the methane abundance with depth.
ABSTRACT
We present spectra of Eris from the MMT 6.5 m Telescope and Red Channel Spectrograph (5700–9800 Å, 5 Å pixel
−1
) on Mt. Hopkins, AZ, and of Pluto from the Steward Observatory 2.3 m ...Telescope and Boller and Chivens Spectrograph (7100–9400 Å, 2 Å pixel
−1
) on Kitt Peak, AZ. In addition, we present laboratory transmission spectra of methane–nitrogen and methane–argon ice mixtures. By anchoring our analysis in methane and nitrogen solubilities in one another as expressed in the phase diagram of Prokhvatilov & Yantsevich, and comparing methane bands in our Eris and Pluto spectra and methane bands in our laboratory spectra of methane and nitrogen ice mixtures, we find Eris' bulk methane and nitrogen abundances are ∼10% and ∼90% and Pluto's bulk methane and nitrogen abundances are ∼3% and ∼97%. Such abundances for Pluto are consistent with values reported in the literature. It appears that the bulk volatile composition of Eris is similar to the bulk volatile composition of Pluto. Both objects appear to be dominated by nitrogen ice. Our analysis also suggests, unlike previous work reported in the literature, that the methane and nitrogen stoichiometry is constant with depth into the surface of Eris. Finally, we point out that our Eris spectrum is also consistent with a laboratory ice mixture consisting of 40% methane and 60% argon. Although we cannot rule out an argon-rich surface, it seems more likely that nitrogen is the dominant species on Eris because the nitrogen ice 2.15 μm band is seen in spectra of Pluto and Triton.
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 semimajor
axis a 45 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.
Four years ago, we reported that the surface colors of ancient, icy bodies at and beyond the orbit of Neptune—Kuiper belt objects— divide into two distinct color populations. Our report has proven ...quite controversial. Specifically, every other research group looking with large telescopes at Kuiper belt objects finds a continuous range of colors rather than two distinct populations. Here we report new color measurements of 18 objects, primarily from the Keck I 10-m telescope, that confirm the existence of two populations. We have combined the color measurements of the other groups to create a data set comparable in size to our data set. We have carried out a Monte Carlo statistical analysis and found that both data sets are consistent with two color populations and our data set, which has smaller uncertainties, rules out a continuum of colors. In addition, our new observations and those in the literature confirm our earlier report that classical KBOs with perihelion distances beyond 40 AU exhibit extremely red surface colors. Our results rule out a continuous color distribution for both our complete sample and subsamples with perihelion distances greater than or less than 40 AU. We suspect the color patterns will result in a better understanding of the formation and evolution of the outer Solar System.
We present new optical broadband colors, obtained with the Keck 1 and Vatican Advanced Technology telescopes, for six objects in the inner classical Kuiper Belt. Objects in the inner classical Kuiper ...Belt are of interest as they may represent the surviving members of the primordial Kuiper Belt that formed interior to the current position of the 3:2 resonance with Neptune, the current position of the plutinos, or, alternatively, they may be objects formed at a different heliocentric distance that were then moved to their present locations. The six new colors, combined with four previously published, show that the ten inner belt objects with known colors form a neutral clump and a reddish clump in B--R color. Nonparametric statistical tests show no significant difference between the B--R color distribution of the inner disk objects compared to the color distributions of Centaurs, plutinos, or scattered disk objects. However, the B--R color distribution of the inner classical Kuiper Belt Objects does differ significantly from the distribution of colors in the cold (low inclination) main classical Kuiper Belt. The cold main classical objects are predominately red, while the inner classical belt objects are a mixture of neutral and red. The color difference may reveal the existence of a gradient in the composition and/or surface processing history in the primordial Kuiper Belt, or indicate that the inner disk objects are not dynamically analogous to the cold main classical belt objects.
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