4,516 research outputs found
The bimodal color distribution of small Kuiper Belt objects
We conducted a two-night photometric survey of small Kuiper Belt objects
(KBOs) near opposition using the wide-field Hyper Suprime-Cam instrument on the
8.2 m Subaru Telescope. The survey covered about 90 deg^2 of sky, with each
field imaged in the g and i bands. We detected 356 KBOs, ranging in absolute
magnitude from 6.5 to 10.4. Filtering for high-inclination objects within the
hot KBO population, we show that the g-i color distribution is strongly
bimodal, indicative of two color classes - the red and very red subpopulations.
After categorizing objects into the two subpopulations by color, we present the
first dedicated analysis of the magnitude distributions of the individual color
subpopulations and demonstrate that the two distributions are roughly identical
in shape throughout the entire size range covered by our survey. Comparing the
color distribution of small hot KBOs with that of Centaurs, we find that they
have similar bimodal shapes, thereby providing strong confirmation of previous
explanations for the attested bimodality of Centaurs. We also show that the
magnitude distributions of the two KBO color subpopulations and the two color
subpopulations observed in the Jupiter Trojans are statistically
indistinguishable. Finally, we discuss a hypothesis describing the origin of
the KBO color bimodality based on our survey results.Comment: 9 pages, 6 figures, accepted for publication in AJ, supplemental
table accessible on online journa
Multiband photometry of a Patroclus-Menoetius mutual event: Constraints on surface heterogeneity
We present the first complete multiband observations of a binary asteroid
mutual event. We obtained high-cadence, high-signal-to-noise photometry of the
UT 2018 April 9 inferior shadowing event in the Jupiter Trojan binary system
Patroclus-Menoetius in four Sloan bands , , , and . We use
an eclipse lightcurve model to fit for a precise mid-eclipse time and estimate
the minimum separation of the two eclipsing components during the event. Our
best-fit mid-eclipse time of is 19
minutes later than the prediction of Grundy et al. (2018); the minimum
separation between the center of Menoetius' shadow and the center of Patroclus
is km slightly larger than the predicted 69.5 km. Using the
derived lightcurves, we find no evidence for significant albedo variations or
large-scale topographic features on the Earth-facing hemisphere and limb of
Patroclus. We also apply the technique of eclipse mapping to place an upper
bound of 0.15 mag on wide-scale surface color variability across
Patroclus.Comment: 5 pages, 3 figures, accepted for publication in A
A hypothesis for the color bimodality of Jupiter Trojans
One of the most enigmatic and hitherto unexplained properties of Jupiter
Trojans is their bimodal color distribution. This bimodality is indicative of
two sub-populations within the Trojans, which have distinct size distributions.
In this paper, we present a simple, plausible hypothesis for the origin and
evolution of the two Trojan color sub-populations. In the framework of
dynamical instability models of early Solar System evolution, which suggest a
common primordial progenitor population for both Trojans and Kuiper belt
objects, we use observational constraints to assert that the color bimodalities
evident in both minor body populations developed within the primordial
population prior to the onset of instability. We show that, beginning with an
initial composition of rock and ices, location-dependent volatile loss through
sublimation in this primordial population could have led to sharp changes in
the surface composition with heliocentric distance. We propose that the
depletion or retention of HS ice on the surface of these objects was the
key factor in creating an initial color bimodality. Objects that retained
HS on their surfaces developed characteristically redder colors upon
irradiation than those that did not. After the bodies from the primordial
population were scattered and emplaced into their current positions, they
preserved this primordial color bimodality to the present day. We explore
predictions of the volatile loss model - in particular, the effect of
collisions within the Trojan population on the size distributions of the two
sub-populations - and propose further experimental and observational tests of
our hypothesisComment: 8 pages, 3 figures, accepted for publication in A
Photometry of active Centaurs: Colors of dormant active Centaur nuclei
We present multiband photometric observations of nine Centaurs. Five of the
targets are known active Centaurs (167P/CINEOS, 174P/Echeclus, P/2008 CL94,
P/2011 S1, and C/2012 Q1), and the other four are inactive Centaurs belonging
to the redder of the two known color subpopulations (83982 Crantor, 121725
Aphidas, 250112 2002 KY14, and 281371 2008 FC76). We measure the optical colors
of eight targets and carry out a search for cometary activity. In addition to
the four inactive Centaurs, three of the five active Centaurs showed no signs
of activity at the time of observation, yielding the first published color
measurements of the bare nuclei of 167P and P/2008 CL94 without possible coma
contamination. Activity was detected on P/2011 S1 and C/2012 Q1, yielding
relatively high estimated mass loss rates of and kg/s,
respectively. The colors of the dormant nuclei are consistent with the
previously-published colors, indicating that any effect of non-geometric
scattering from Centaur dust or blanketing debris on the measured colors is
minimal. The results of our observations are discussed in the context of the
cause of Centaur activity and the color distributions of active and inactive
Centaurs. We suggest that the relative paucity of red Centaurs with
low-perihelion orbits may not be directly due to the blanketing of the surface
by unweathered particulates, but could instead be a result of the higher levels
of thermal processing on low-perihelion Centaurs in general.Comment: 13 pages, 4 figures, accepted for publication in A
The differing magnitude distributions of the two Jupiter Trojan color populations
The Jupiter Trojans are a significant population of minor bodies in the
middle Solar System that have garnered substantial interest in recent years.
Several spectroscopic studies of these objects have revealed notable
bimodalities with respect to near-infrared spectra, infrared albedo, and color,
which suggest the existence of two distinct groups among the Trojan population.
In this paper, we analyze the magnitude distributions of these two groups,
which we refer to as the red and less red color populations. By compiling
spectral and photometric data from several previous works, we show that the
observed bimodalities are self-consistent and categorize 221 of the 842 Trojans
with absolute magnitudes in the range H<12.3 into the two color populations. We
demonstrate that the magnitude distributions of the two color populations are
distinct to a high confidence level (>95%) and fit them individually to a
broken power law, with special attention given to evaluating and correcting for
incompleteness in the Trojan catalog as well as incompleteness in our
categorization of objects. A comparison of the best-fit curves shows that the
faint-end power-law slopes are markedly different for the two color
populations, which indicates that the red and less red Trojans likely formed in
different locations. We propose a few hypotheses for the origin and evolution
of the Trojan population based on the analyzed data.Comment: Published in AJ; 26 pages, 7 figure
The Color–Magnitude Distribution of Hilda Asteroids: Comparison with Jupiter Trojans
Current models of solar system evolution posit that the asteroid populations in resonance with Jupiter are comprised of objects scattered inward from the outer solar system during a period of dynamical instability. In this paper, we present a new analysis of the absolute magnitude and optical color distribution of Hilda asteroids, which lie in 3:2 mean-motion resonance with Jupiter, with the goal of comparing the bulk properties with previously published results from an analogous study of Jupiter Trojans. We report an updated power-law fit of the Hilda magnitude distribution through H = 14. Using photometric data listed in the Sloan Moving Object Catalog, we confirm the previously reported strong bimodality in visible spectral slope distribution, indicative of two subpopulations with differing surface compositions. When considering collisional families separately, we find that collisional fragments follow a unimodal color distribution with spectral slope values consistent with the bluer of the two subpopulations. The color distributions of Hildas and Trojans are comparable and consistent with a scenario in which the color bimodality in both populations developed prior to emplacement into their present-day locations. We propose that the shallower magnitude distribution of the Hildas is a result of an initially much larger Hilda population, which was subsequently depleted as smaller bodies were preferentially ejected from the narrow 3:2 resonance via collisions. Altogether, these observations provide a strong case supporting a common origin for Hildas and Trojans as predicted by current dynamical instability theories of solar system evolution
Hubble Ultraviolet Spectroscopy of Jupiter Trojans
We present the first ultraviolet spectra of Jupiter Trojans. These
observations were carried out using the Space Telescope Imaging Spectrograph on
the Hubble Space Telescope and cover the wavelength range 200-550 nm at low
resolution. The targets include objects from both of the Trojan color
subpopulations (less-red and red). We do not observe any discernible absorption
features in these spectra. Comparisons of the averaged UV spectra of less-red
and red targets show that the subpopulations are spectrally distinct in the UV.
Less-red objects display a steep UV slope and a rollover at around 450 nm to a
shallower visible slope, whereas red objects show the opposite trend.
Laboratory spectra of irradiated ices with and without HS exhibit
distinct UV absorption features; consequently, the featureless spectra observed
here suggest HS alone is not responsible for the observed color
bimodality of Trojans, as has been previously hypothesized. We propose some
possible explanations for the observed UV-visible spectra, including complex
organics, space weathering of iron-bearing silicates, and masked features due
to previous cometary activity.Comment: 7 pages, 4 figures, accepted by A
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