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Post Info TOPIC: Smallest Kuiper Belt Object
Blobrana


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Title: Initial Planetesimal Sizes and the Size Distribution of Small Kuiper Belt Objects
Authors: Hilke E. Schlichting, Cesar I. Fuentes, David E. Trilling

We show, by comparing observations with theoretical models, that the observed Kuiper Belt size distribution is well matched by coagulation models, which start from an initial planetesimal population with radii of about 1km, and subsequent collisional evolution. We find that the observed size distribution for R > 30km has not been modified by collisional evolution over the age of the solar system, and that the size distribution below R ~ 30km has been modified by collisions and that its slope is well matched by collisional evolution models that use published strength laws. We investigate in detail the resulting size distribution of bodies ranging from 0.01km to 30km and find that its slope changes several times as a function of radius before approaching the expected value for an equilibrium collisional cascade of material strength dominated bodies for R < 0.1km. Compared to a single power law size distribution that would span the whole range from 0.01km to 30km, we find a strong deficit of bodies around R ~10km and a strong excess of bodies around 2km. This deficit and excess are caused by an excess mass in small planetesimals in the km size range that was left over from the runaway growth phase and that leaves a signature in the size distribution that is not erased after 4.5 Gyrs of collisional evolution.
Observations of the small KBO size distribution can therefore test if large KBOs grew as a result of runaway growth and constrain the initial planetesimal sizes. We find that results from recent KBO occultation surveys and the observed KBO size distribution can be best matched by an initial planetesimal population that contained about equal mass per logarithmic mass bin in bodies ranging from 0.4km to 4km in radius. In addition, we find that we cannot match the observed KBO size distribution if most of the planetesimal mass was contained in bodies that were 10km in radius or larger.

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Blobrana


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Scientists find smallest known Pluto sibling
At one-third of a mile wide, it sets new record for tiniest Kuiper Belt object

The frozen worlds orbiting beyond Neptune include not only dwarf planets like Pluto and Ceres, but also a tiny, icy toehold just one-third of a mile wide.
The discovery, made by a team of astronomers scouring Hubble Space Telescope observations, sets a new record for the smallest Kuiper Belt object found. Previously, the smallest known Pluto sibling was a 30-mile-wide Kuiper Belt object.
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Blobrana


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Title: A single sub-kilometre Kuiper belt object from a stellar occultation in archival data
Authors: H. E. Schlichting, E. O. Ofek, M. Wenz, R. Sari, A. Gal-Yam, M. Livio, E. Nelan and S. Zucker

The Kuiper belt is a remnant of the primordial Solar System. Measurements of its size distribution constrain its accretion and collisional history, and the importance of material strength of Kuiper belt objects. Small, sub-kilometre-sized, Kuiper belt objects elude direct detection, but the signature of their occultations of background stars should be detectable. Observations at both optical10 and X-ray11 wavelengths claim to have detected such occultations, but their implied abundances are inconsistent with each other and far exceed theoretical expectations. Here we report an analysis of archival data that reveals an occultation by a body with an approximately 500-metre radius at a distance of 45 astronomical units. The probability of this event arising from random statistical fluctuations within our data set is about two per cent. Our survey yields a surface density of Kuiper belt objects with radii exceeding 250 metres of 2.1^(+4.8)_(-1.7) x 10^7 deg^-2 , ruling out inferred surface densities from previous claimed detections by more than 5 sigma. The detection of only one event reveals a deficit of sub-kilometre-sized Kuiper belt objects compared to a population extrapolated from objects with radii exceeding 50 kilometres. This implies that sub-kilometre-sized objects are undergoing collisional erosion, just like debris disks observed around other stars.

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-- Edited by Blobrana on Thursday 17th of December 2009 08:02:12 PM

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Blobrana


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A California scientist using the Hubble Space Telescope has discovered the smallest object ever seen in the Kuiper Belt - the vast region of icy objects beyond the orbit of Neptune.
The unnamed object is estimated to be 3,200 feet in diameter - just over a half-mile. Hubble detected it from 4.2 billion miles. The next-smallest known Kuiper Belt object is 30 miles in diameter.
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Blobrana


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NASA's Hubble Space Telescope has discovered the smallest object ever seen in visible light in the Kuiper Belt, a vast ring of icy debris that is encircling the outer rim of the solar system just beyond Neptune.
The needle-in-a-haystack object found by Hubble is only 3,200 feet across and a whopping 4.2 billion miles away. The smallest Kuiper Belt Object (KBO) seen previously in reflected light is roughly 30 miles across, or 50 times larger.
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