Article Summary #13

A single sub-kilometre Kuiper belt object from a stellar occultation in archival data

H. E. Schlichting, E. O. Ofek, M. Wenz et al. 2009, Nature, 462, 895
http://www.nature.com/nature/journal/v462/n7275/full/nature08608.html

In our Solar System one remnant from its early evolutionary state is the Kuiper belt, a flow of material found beyond Neptune that orbits the Sun. For this system, size distribution is crucial because it can give information about the physical history of the Kuiper belt and the objects that it consists of.

Because the Kuiper belt is located so far from the Earth, the direct detection on small objects (<1km in diameter) is not possible, but they their effects can be observed: they cause occultations which are changes in the light curve due to the object’s obscuration of a star located in the background. The variation cause a diffraction pattern of the radiation emitted by the background star which depends on several factors: the Kuiper belt object’s size and distance, angular size of the star and other additional parameters.

Thus, by looking at the occultations, Schlichting et al. 2009 detected object with a radius of ~500m, located at a distance of ~45AU (astronomical units). The probability of result being a cause of random statistical error is almost zero, which is a strong proof of the accuracy of the detection.

Since out of all the Kuiper belt objects observed so far this event has been unique. Schlichting et al. 2009 believe that there is a deficit of these small Kuiper belt objects in comparison with the ones that have radii bigger than 50km, distribution which can be explained through the fact that the sub-kilometer objects are experiencing erosion through collisions.