An Improved Approach to Orbital Determination and Prediction of Near-Earth Asteroids: Computer Simulation, Modeling and Test Measurements

In this article, theory-based analytical methodologies of astrophysics employed in the modern era are suitably operated alongside a test research-grade telescope to image and determine the orbit of a near-earth asteroid from original observations, measurements, and calculations. Subsequently, its intrinsic orbital path has been calculated including the chance it would likely impact Earth in the time ahead. More so specifically, this case-study incorporates the most effective, feasible, and novel Gausss Method in order to maneuver the orbital plane components of a planetesimal, further elaborating and extending our probes on a selected near-earth asteroid (namely the 12538-1998 OH) through the observational data acquired over a six week period. Utilizing the CCD (Charge Coupled Device) snapshots captured, we simulate and calculate the orbit of our asteroid as outlined in quite detailed explanations. The uncertainties and deviations from the expected values are derived to reach a judgement whether our empirical findings are truly reliable and representative measurements by partaking a statistical analysis based systematic approach. Concluding the study by narrating what could have caused such discrepancy of findings in the first place, if any, measures are put forward that could be undertaken to improve the test-case for future investigations. Following the calculation of orbital elements and their uncertainties using Monte Carlo analysis, simulations were executed with various sample celestial bodies to derive a plausible prediction regarding the fate of Asteroid 1998 OH. Finally, the astrometric and photometric data, after their precise verification, were officially submitted to the Minor Planet Center: an organization hosted by the Center for Astrophysics, Harvard and Smithsonian and funded by NASA, for keeping track of the asteroids potential trajectories.

The alignment of interstellar dust grains: thermal flipping and the Davis-Greenstein mechanism

Interstellar dust grains are non-spherical and, in some environments, partially aligned along the direction of the interstellar magnetic field. Numerous alignment theories have been proposed, all of which examine the grain rotational dynamics. In 1999, Lazarian & Draine introduced the important concept of thermal flipping, in which internal relaxation processes induce the grain body to flip while its angular momentum remains fixed. Through detailed numerical simulations, we study the role of thermal flipping on the grain dynamics during periods of relatively slow rotation, known as `crossovers, for the special case of a spheroidal grain with a non-uniform mass distribution. Lazarian & Draine proposed that rapid flipping during a crossover would lead to `thermal trapping, in which a systematic torque, fixed relative to the grain body, would time average to zero, delaying spin-up to larger rotational speeds. We find that the time-averaged systematic torque is not zero during the crossover and that thermal trapping is not prevalent. As an application, we examine whether the classic Davis-Greenstein alignment mechanism is viable, for grains residing in the cold neutral medium and lacking superparamagnetic inclusions. We find that Davis-Greenstein alignment is not hindered by thermal trapping, but argue that it is, nevertheless, too inefficient to yield the alignment of large grains responsible for optical and infrared starlight polarization. Davis-Greenstein alignment of small grains could potentially contribute to the observed ultraviolet polarization. The theoretical and computational tools developed here can also be applied to analyses of alignment via radiative torques and rotational disruption of grains.