A New General Perturbation Method for Determining the Long-Term Motion of Comets
Issue:
Volume 11, Issue 1, March 2023
Pages:
1-6
Received:
14 October 2022
Accepted:
6 January 2023
Published:
21 February 2023
Abstract: A number of authors have used special perturbation methods to propagate Comet Halley back before its oldest observation in 239 BC. Unfortunately, results from these studies vary drastically because it is so difficult to accurately model nongraviatational forces acting on comets. In contrast, general perturbation methods do not need to model any forces and can be more accurate over long periods of time. Regrettably, the most recent general perturbation method used for Comet Halley introduced a lot of subjectivity. A new general perturbation method integrating Halley’s Comet back in time is presented here. This new method uses least squares, based solely on math. Therefore, it does not introduce any subjectivity. It also permits statistical analysis of the model’s accuracy. Using this model, Halley’s Comet is propagated back to 2317 BC, and with the derived equations it can easily be integrated back much further in time. Results are very similar to two previous studies by other authors, varying by less than five years when propagated back over 2,200 years. This same new general perturbation method is also applied to Comet Swift-Tuttle. Results with Swift-Tuttle compare reasonably well with the only other known research that integrated this comet back in time.
Abstract: A number of authors have used special perturbation methods to propagate Comet Halley back before its oldest observation in 239 BC. Unfortunately, results from these studies vary drastically because it is so difficult to accurately model nongraviatational forces acting on comets. In contrast, general perturbation methods do not need to model any for...
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Effects of Spin Properties on Braking Indices of 208 Glitching Pulsars
Juliana Nwakaego Odo,
Azubuike Christian Ugwoke
Issue:
Volume 11, Issue 1, March 2023
Pages:
7-14
Received:
8 March 2023
Accepted:
4 April 2023
Published:
24 April 2023
Abstract: Pulsars are stars that emit electromagnetic radiation in a definite time interval. Detailed study of the long-term timing observations of pulsars indicate that the predictable smooth spin- down of pulsars is predisposed to discrete fluctuations known as glitch. The rotation frequency of pulsars decays with time as quantified by the braking index (n). The braking indices have been known to have no consequence on the quantities like obliquity angle evolution or complex high-order multipole structure but on the spin properties of the pulsars. In the canonical model of the theory of braking indices, n = 3 for all pulsars, but observational information has shown that n ≠ 3, indicating that the canonical model requires reconsideration. Using the Australian Telescope National Facility (ATNF) pulsar catalogue, we selected 208 pulsars with 670 glitches and used the distributions of the spin properties to statistically investigate their effects on the braking indices. We computed the braking indices of these pulsars using the theoretical method and observed that the braking index is much smaller for very young pulsars (104-107) which have been observed to show more glitch activity than their old, stable counterparts. A simple regression analysis of our data show that spin properties of pulsar are more than 65% correlated with the magnitude of pulsar braking index. The implications of the spin properties on braking indices on long timescales are discussed.
Abstract: Pulsars are stars that emit electromagnetic radiation in a definite time interval. Detailed study of the long-term timing observations of pulsars indicate that the predictable smooth spin- down of pulsars is predisposed to discrete fluctuations known as glitch. The rotation frequency of pulsars decays with time as quantified by the braking index (n...
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