Distribution Of Kuiper Belt Objects Research Articles

New Horizons Venetia Burney Student Dust Counter Observes Higher than Expected Fluxes Approaching 60 au

The NASA New Horizons Venetia Burney Student Dust Counter (SDC) measures dust particle impacts along the spacecraft’s flight path for grains with mass ≥10−12 g, mapping out their spatial density distribution. We present the latest SDC dust density, size distribution, and flux measurements through 55 au and compare them to numerical model predictions. Kuiper Belt objects (KBOs) are thought to be the dominant source of interplanetary dust particles in the outer solar system due to both collisions between KBOs and their continual bombardment by interstellar dust particles. Continued measurements through 55 au show higher than model-predicted dust fluxes as New Horizons approaches the putative outer edge of the Kuiper Belt (KB). We discuss potential explanations for the growing deviation: radiation pressure stretches the dust distribution to further heliocentric distances than its parent body distribution; icy dust grains undergo photosputtering that rapidly increases their response to radiation pressure forces and pushes them further away from the Sun; and the distribution of KBOs may extend much further than existing observations suggest. Ongoing SDC measurements at even larger heliocentric distances will continue to constrain the contributions of dust production in the KB. Continued SDC measurements remain crucial for understanding the Kuiper Belt and the interpretation of dust disks around other stars.

Fast Algorithms for Slow Moving Asteroids: Constraints on the Distribution of Kuiper Belt Objects

Abstract We introduce a new computational technique for searching for faint moving sources in astronomical images. Starting from a maximum-likelihood estimate for the probability of the detection of a source within a series of images, we develop a massively parallel algorithm for searching through candidate asteroid trajectories that utilizes graphics processing units (GPU). This technique can search over 1010 possible asteroid trajectories in stacks of the order of 10–15 4K × 4K images in under a minute using a single consumer grade GPU. We apply this algorithm to data from the 2015 campaign of the High Cadence Transient Survey (HiTS) obtained with the Dark Energy Camera (DECam). We find 39 previously unknown Kuiper belt objects (KBOs) in the 150 square degrees of the survey. Comparing these asteroids to an existing model for the inclination distribution of the Kuiper belt we demonstrate that we recover a KBO population above our detection limit consistent with previous studies. Software used in this analysis is made available as an open source package.

Constraints on the location of a possible 9th planet derived from theCassinidata

To explain the unusual distribution of Kuiper belt objects, several authors have advocated the existence of a super-Earth planet in the outer solar system. It has recently been proposed that a 10 M⊕ object with an orbit of 700 AU semi major axis and 0.6 eccentricity can explain the observed distribution of Kuiper belt objects around Sedna. Here we use the INPOP planetary ephemerides model as a sensor for testing for an additional body in the solar system. We test the possibility of adding the proposed planet without increasing the residuals of the planetary ephemerides, fitted over the whole INPOP planetary data sample. We demonstrate that the presence of such an object is not compatible with the most sensitive data set, the Cassini radio ranging data, if its true anomaly is in the intervals [−130°: −100° ] or [−65°:85° ]. Moreover, we find that the addition of this object can reduce the Cassini residuals, with a most probable position given by a true anomaly v = 117.8°+11°-10° .

On the roles of escape erosion and the viscous relaxation of craters on Pluto

Pluto and its satellites will be the most distant objects ever reconnoitered when NASA’s New Horizons spacecraft conducts its intensive flyby of this system in 2015. The size-frequency distribution (SFD) of craters on the surfaces in the Pluto system have long been expected to provide a useful measure of the size distribution of Kuiper Belt Objects (KBOs) down to much smaller size scales than presently observed. However, currently predicted escape rates of Pluto’s atmosphere suggest that of order one-half to several kilometers of nitrogen ice has been removed from Pluto’s surface over geologic time. Because this range of depths is comparable to or greater than most expected crater depths on Pluto, one might expect that many craters on Pluto’s surface may have been removed or degraded by this process, biasing the observed crater SFD relative to the production–function crater SFD. Further, if Pluto’s surface volatile layer is comparable to or deeper than crater depths, and if the viscosity of this layer surface ice is low like the viscosity of pure N2 ice at Pluto’s measured 35K surface temperature (or as low as the viscosity of CH4 ice at warmer but plausible temperatures on isolated pure-CH4 surfaces on Pluto), then craters on Pluto may also have significantly viscously relaxed, also potentially biasing the observed crater SFD and surface crater retention age. Here we make a first exploration of how these processes can affect the displayed cratering record on Pluto. We find that Pluto’s surface may appear to be younger owing to these effects than it actually is. We also find that by comparing Pluto’s cratering record to Charon’s, it may be possible to estimate the total loss depth of material from Pluto’s surface over geologic time, and therefore to estimate Pluto’s time-averaged escape rate.

SYSTEMATIC BIASES IN THE OBSERVED DISTRIBUTION OF KUIPER BELT OBJECT ORBITS

The orbital distribution of Kuiper Belt objects (KBOs) provides important tests of solar system evolution models. However, our understanding of this orbital distribution can be affected by many observational biases. An important but difficult to quantify bias results from tracking selection effects; KBOs are recovered or lost depending on assumptions made about their orbital elements when fitting the initial (short) observational arc. Quantitatively studying the effects and significance of this bias is generally difficult, because only the objects where the assumptions were correct are recovered and thus available to study “the problem,” and because different observers use different assumptions and methods. We have used a sample of 38 KBOs that were discovered and tracked, bias-free, as part of the Canada–France Ecliptic Plane Survey to evaluate the potential for losing objects based on the two most common orbit and ephemeris prediction sources: the Minor Planet Center (MPC) and the Bernstein and Khushalani (BK) orbit fitting code. In both cases, we use early discovery and recovery astrometric measurements of the objects to generate ephemeris predictions that we then compare to later positional measurements; objects that have large differences between the predicted and actual positions would be unlikely to be recovered and are thus considered “lost.” We find systematic differences in the orbit distributions which would result from using the two orbit-fitting procedures. In our sample, the MPC-derived orbit solutions lost slightly fewer objects (five out of 38) due to large ephemeris errors at one year recovery, but the objects which were lost belonged to more “unusual” orbits such as scattering disk objects or objects with semimajor axes interior to the 3:2 resonance. Using the BK code, more objects (seven out of 38) would have been lost due to ephemeris errors, but the lost objects came from a range of orbital regions, primarily the classical belt region. We also compare the accuracy of orbits calculated from one year arcs against orbits calculated from multiple years of observations and find that two-opposition orbits without additional observations acquired at least two months from opposition are unreliable for dynamical modeling.

Detectability of Occultations of Stars by Objects in the Kuiper Belt and Oort Cloud

The serendipitous detection of stellar occultations by outer solar system objects is a powerful method for ascertaining the small end (r 15 km) of the size distribution of Kuiper Belt objects and may potentially allow the exploration of objects as far out as the Oort Cloud. The design and implementation of an occultation survey is aided by a detailed understanding of how diffraction and observational parameters affect the detection of occultation events. In this study, stellar occultations are simulated, accounting for diffraction effects, finite source sizes, finite bandwidths, stellar spectra, sampling, and signal-to-noise ratios. Finally, the possibility of detecting small outer solar system objects from the Kuiper Belt all the way out to the Oort Cloud is explored for three photometric systems: a proposed space telescope, Whipple, the Taiwanese-American Occultation Survey, and the MMT.

A Signature of Planetary Migration: The Origin of Asymmetric Capture in the 2 : 1 Resonance

The spatial distribution of Kuiper Belt objects (KBOs) in 2 : 1 exterior resonance with Neptune constrains that planet's migration history. Numerical simulations demonstrate that fast planetary migration generates a larger population of KBOs trailing rather than leading Neptune in orbital longitude. This asymmetry corresponds to a greater proportion of objects caught into asymmetric resonance such that their resonance angles ϕ librate about values greater than π (trailing) as opposed to less than π (leading). We provide, for the first time, an explanation of this phenomenon, using physical, analytic, and semianalytic arguments. Central to our understanding is how planetary migration shifts the equilibrium points of the superposed direct and indirect potentials. Symmetric libration, in which ϕ librates about ~π, precedes capture into asymmetric resonance. As a particle transitions from symmetric to asymmetric libration, if ϕ exceeds the value ψ at the unstable point of asymmetric resonance, then the particle is caught into trailing resonance, while if ϕ < ψ, the particle is caught into leading resonance. The probability that the KBO is caught into trailing resonance is determined by the fraction of time it spends with ϕ > ψ while in symmetric libration. This fractional time increases with faster migration because migration not only shifts ψ to values less than π but also shifts the stable point of symmetric libration to values greater than π. Smaller eccentricities prior to capture strengthen the effect of these shifts. Large capture asymmetries appear for exponential timescales of migration τ shorter than ~107 yr. The observed distribution of 2 : 1 KBOs (two trailing and seven leading) excludes τ ≤ 106 yr with 99.65% confidence.

Shaping the Kuiper belt size distribution by shattering large but strengthless bodies

The observed size distribution of Kuiper belt objects (KBOs)—small icy and rocky Solar System bodies orbiting beyond Neptune—is well described by a power law at large KBO sizes. However, recent work by Bernstein et al. (2004, Astron. J. 128, 1364–1390) indicates that the size distribution breaks and becomes shallower for KBOs smaller than about 70 km in size. Here we show that we expect such a break at KBO radius ∼ 40 km since destructive collisions are frequent for smaller KBOs. Specifically, we assume that KBOs are gravity-dominated bodies with negligible material strength. This gives a power-law slope q ≃ 3 where the number N > r of KBOs larger than a size r is given by N > r ∝ r 1 − q ; the break location follows from this slope through a self-consistent calculation. The existence of this break, the break's location, and the power-law slope we expect below the break are consistent with the findings of Bernstein et al. (2004, Astron. J. 128, 1364–1390). The agreement with observations indicates that KBOs as small as ∼ 40 km are effectively strengthless.

Cratering rates in the outer Solar System

This paper is a compilation by table, graph, and equation of impact cratering rates from Jupiter to Pluto. We use several independent constraints on the number of ecliptic comets. Together they imply that the impact rate on Jupiter by 1.5-km-diameter comets is currently Ṅ( d > 1.5 km) = 0.005−0.003+0.006 per annum. Other kinds of impactors are currently unimportant on most worlds at most sizes. The size–number distribution of impactors smaller than 20 km is inferred from size–number distributions of impact craters on Europa, Ganymede, and Triton; while the size–number distribution of impacting bodies larger than 50 km is equated to the size–number distribution of Kuiper Belt objects. The gap is bridged by interpolation. It is notable that small craters on Jupiter’s moons indicate a pronounced paucity of small impactors, while small craters on Triton imply a collisional population rich in small bodies. However it is unclear whether the craters on Triton are of heliocentric or planetocentric origin. We therefore consider two cases for Saturn and beyond: a Case A in which the size–number distribution is like that inferred at Jupiter, and a Case B in which small objects obey a more nearly collisional distribution. Known craters on saturnian and uranian satellites are consistent with either case, although surface ages are much younger in Case B, especially at Saturn and Uranus. At Neptune and especially at Saturn our cratering rates are much higher than rates estimated by Shoemaker and colleagues, presumably because Shoemaker’s estimates mostly predate discovery of the Kuiper Belt. We also estimate collisional disruption rates of moons and compare these to estimates in the literature.

The characteristics of orbital distribution of Kuiper belt objects

A statistical analysis of the orbital semi-major axes of Kuiper belt objects (KBOs) shows that the mass weighted mean of the heliocentric distances of 528 trans-Neptunian objects (TNOs) is 43.3 AU, and that except the Plutinos (i.e., “Little Plutos”) in the 3:2 Neptune resonance region their radial distribution is approximately a normal distribution with maximum at about 43 AU. This distribution cannot be interpreted with resonant capture mechanism. But it is similar to the radial distribution of particles in a protoplanetary nebula computed with the author's simulative quantum theory. Comparing with the normal distribution, we find that there is an absence of objects in the range between the 3:2 Neptune resonance and 43 AU. The distribution of eccentricities of the TNOs suggests that the absent objects might have been removed into the resonance region.

Stochastic effects in the planet migration and orbital distribution of the Kuiper Belt

Assuming the Jovian planets experienced smooth orbital migrations, Malhotra successfully explained some important features of the Kuiper Belt by the mechanism of resonance capture. However, the migration should really be stochastic. In this paper we numerically simulate numerous orbital evolutions of test particles under such stochastic planet migrations. The main results are as follows. Given the proper parameters, the concentration of objects in the 3 : 2 resonance is distinct, while very few objects enter the 2 : 1 resonance, and consequently, the orbital distribution of Kuiper Belt objects matches the observational data very well. The stochastic effects excite the orbital eccentricities and inclinations of objects in the non-resonant regions. The introduction of stochastic effects also gives possible explanations of the mass depletion, and of the sources of the classical and scattered Kuiper Belt objects.