We present recovery observations of the parent of the Leonid meteor stream – comet 55P/Tempel-Tuttle using the Keck II telescope. At recovery, the comet was at r = 4.5 AU, with m R = 22.6, and there was no indication of coma or activity. Pre-and post-recovery observations from 6 observing runs (1994–1997 June) are presented. From these measurements we estimate that the nucleus radius is R N = 1...

The recently discovered comet Hale-Bopp (C/1995 01) sports a bright dust coma even though it is still far from the sun (presently 6 astronomical units). This feature has attracted considerable interest in the public and scientific arenas. The comet is headed toward perihelion at 0.92 astronomical unit in April 1997 and is widely expected to then become a spectacular naked-eye comet. With millim...

This paper describes the CoMeT system, our contribution to the SemEval 2013 Task 7 challenge, focusing on the task of automatically assessing student answers to factual questions. CoMeT is based on a meta-classifier that uses the outputs of the sub-systems we developed: CoMiC, CoSeC, and three shallower bag approaches. We sketch the functionality of all sub-systems and evaluate their performanc...

Planet formation is accompanied by the formation of comet clouds. In systems where planets migrate on rapid timescales, the diffusive evolution of comet orbits may stall, resulting in a comet cloud intermediate between a flattened Kuiper Belt and a spherical Oort cloud. These ‘failed Oort clouds’ may provide a ‘smoking gun’, indicating that planetary migration has taken place. If some fraction ...

use of different pesticides in the agriculture sector, in order to boost crop yield within a short time period and low labor, has been tremendously increased since the last decade. pesticide use has elevated crop yield but has produced a number of pronounced problems regarding environmental and health safety. the continuously deteriorating toxicological effects of these pesticides are not only ...

Cometary particles returned by the Stardust Discovery Mission are primarily silicate materials of solar system origin. Some of the grains were formed at high temperatures close to the Sun, but then transported far out to the Kuiper belt region of the solar system before being incorporated in the comet.