Observational bias and the clustering of distant eccentric Kuiper belt objects

The hypothesis that a massive Planet Nine exists in the outer solar system on a distant eccentric orbit was inspired by observations showing that the objects with the most distant eccentric orbits in the Kuiper belt have orbits which are physically aligned, that is, they are clustered in longitude of perihelion and have similar orbital planes. Questions have remained, however, about the effects of observational bias on these observations, particularly on the longitudes of perihelion. Specifically, distant eccentric Kuiper belt objects tend to be faint and only observable near their perihelia, suggesting that the longitudes of perihelion of the known distant objects could be strongly biased by the limited number of locations in the sky where deep surveys have been carried out. We have developed a method to rigorously estimate the longitude of perihelion bias for Kuiper belt observations. We find that the probability that the 10 known Kuiper belt objects with semimajor axis beyond 230 AU are drawn from a population with uniform longitude of perihelion is 1.2%. Combined with the observation that the orbital poles of these object are also clustered, the overall probability of detecting these two independent clusterings in a randomly distributed sample is 0.025%. While observational bias is clearly present in these observations, it is unlikely to explain the observed alignment of the distant eccentric Kuiper belt objects.Comment: AJ, in pres

The 3-4 μ\mum Spectra of Jupiter Trojan Asteroids

To date, reflectance spectra of Jupiter Trojan asteroids have revealed no distinctive absorption features. For this reason, the surface composition of these objects remains a subject of speculation. Spectra have revealed, however, that the Jupiter Trojan asteroids consist of two distinct sub-populations which differ in the optical to near-infrared colors. The origins and compositional differences between the two sub-populations remain unclear. Here we report the results from a 2.2-3.8 $\mu$m spectral survey of a collection of 16 Jupiter Trojan asteroids, divided equally between the two sub-populations. We find clear spectral absorption features centered around 3.1 $\mu$m in the less red population. Additional absorption consistent with expected from organic materials might also be present. No such features are see in the red population. A strong correlation exists between the strength of the 3.1 $\mu$m absorption feature and the optical to near-infrared color of the objects. While traditionally absorptions such as these in dark asteroids are modeled as being due to fine-grain water frost, we find it physically implausible that the special circumstances required to create such fine-grained frost would exist on a substantial fraction of the Jupiter Trojan asteroids. We suggest, instead, that the 3.1 $\mu$m absorption on Trojans and other dark asteroids could be due to N-H stretch features. Additionally, we point out that reflectivities derived from WISE observations show a strong absorption beyond 4$\mu$m for both populations. The continuum of 3.1 $\mu$m features and the common absorption beyond 4 $\mu$m might suggest that both sub-populations of Jupiter Trojan asteroids formed in the same general region of the early solar system.Comment: AJ, in pres

Observation of mass loading in the Io plasma torus

Ground‐based high‐resolution spectra of emission from the Io plasma torus obtained during 53 nights of observation over a seven month period are used to measure the torus rotation speed and discern regions of the torus that are slowed by mass loading of newly ionized materials. The amount of torus slowing implies that between 2000 and 3000 kg sec^(−1) are being ionized by the torus. The slowing is spread azimuthally throughout the orbit of Io, suggesting that neutral materials emanating from Io are distributed around Jupiter much more uniformly than currently believed

Periodicities in the Io plasma torus

We present a 6-month baseline of spatially resolved measurements of the Io plasma torus intensity and perpendicular ion temperature which we use to determine the periodicities of the torus during this time. We find large anticorrelated variations in the intensity and ion temperature which are periodic with the Jovian rotation rate (System III). The intensity variations are found to be a simple manifestation of the temperature variations, though no explanation for the temperature variations is apparent. Periodogram analysis shows an additional intensity periodicity which rotates 2.91±0.06% more slowly than System III. This period is found only in the intensity and not in the ion temperature. We conclude from these observations that the torus has a sinusoidal ion temperature variation locked into the rotation of Jupiter and that superimposed on this is a long-lived density pattern which rotates 2.91% more slowly than Jupiter. Based on the spatial structure and physical properties, we rule out all currently proposed mechanisms for the creation of these periodicities within the torus

Prospects for weak lensing studies with new radio telescopes

I outline the prospects for performing weak lensing studies with the new generation of radio telescopes that are coming online now and in the future. I include a description of a proposed technique to use polarization observations in radio weak lensing analyses which could prove extremely useful for removing a contaminating signal from intrinsic alignments. Ultimately, the Square Kilometre Array promises to be an exceptional instrument for performing weak lensing studies due to the high resolution, large area surveys which it will perform. In the nearer term, the e-MERLIN instrument in the UK offers the high sensitivity and sub-arcsec resolution required to prove weak lensing techniques in the radio band. I describe the SuperCLASS survey -- a recently accepted e-MERLIN legacy programme which will perform a pioneering radio weak lensing analysis of a supercluster of galaxies.Comment: to appear in the proceedings of the 2012 Moriond cosmology meetin

The Inclination Distribution of the Kuiper Belt

We develop a general method for determining the unbiased inclination distribution of the Kuiper belt using only the inclination and latitude of discovery of known Kuiper belt objects (KBOs). These two parameters are well determined for each discovered object, so we can use all 379 known KBOs (as of 2001 January 1)—without knowing the object's precise orbit, area, detection efficiency, or the latitudinal coverage of the survey that found the object—to determine the inclination distribution. We find that a natural analytic form for the inclination distribution is a sine of the inclination multiplied by a Gaussian. The inclination distribution of all KBOs is well fitted by sin i multiplied by a sum of two Gaussians with widths 2°.6^(+.8)_(-.2) and 15° ± 1°. For this inclination distribution, the Kuiper belt has an effective area of 8100^(+1500)-(-1100) deg^2 and a FWHM of 12.5° ± 3.5° in latitude. The inclination distribution of the different dynamical classes appear different. The Plutinos are well fit by sin i mulitplied by a single Gaussian of width 10°.2^(+2.5)_(-1.8), the classical KBOs cannot be fit to a single Gaussian but are well fit by sin i multiplied by the sum of two Gaussians of widths 2°.2^(+.2)_(-.6) and 17° ± 3°, and the scattered KBOs are poorly fit by sin i multiplied by a single Gaussian of width 20° ± 4°. The poor fit of the scattered objects is possibly a result of limitations of the method in dealing with large eccentricities. The effective areas of the Plutinos, classical KBOs, and scattered KBOs are 9300 ± 1800, 6100 ± 2100, and 17000 ± 3000 deg^2, respectively. The FWHMs are 23° ± 5°, 6°.8^(+2.0)_(-3.6), and 44° ± 10°, respectively. In all cases, the inclinations of the Kuiper belt objects appear larger than expected from dynamical simulations of possible perturbations

A case study of student projects for industry clients

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Conformity, deformity and reformity

In any given field of artistic practice, practitioners position themselves—or find themselves positioned—according to interests and allegiances with specific movements, genres, and traditions. Selecting particular frameworks through which to approach the development of new ideas, patterns and expressions, balance is invariably maintained between the desire to contribute towards and connect with a particular set of domain conventions, whilst at the same time developing distinction and recognition as a creative individual. Creativity through the constraints of artistic domain, discipline and style provides a basis for consideration of notions of originality in the context of activity primarily associated with reconfiguration, manipulation and reorganisation of existing elements and ideas. Drawing from postmodern and post-structuralist perspectives in the analysis of modern hybrid art forms and the emergence of virtual creative environments, the transition from traditional artistic practice and notions of craft and creation, to creative spaces in which elements are manipulated, mutated, combined and distorted with often frivolous or subversive intent are considered. This paper presents an educational and musically focused perspective of the relationship between the individual and domain-based creative practice. Drawing primarily from musical and audio-visual examples with particular interest in creative disruption of pre-existing elements, creative strategies of appropriation and recycling are explored in the context of music composition and production. Conclusions focus on the interpretation of creativity as essentially a process of recombination and manipulation and highlight how the relationship between artist and field of practice creates unique creative spaces through which new ideas emerge