On the Validity of “a-jumps” as the Precursors to the Activation of Centaurs
Session 12.07 Spectroscopy
Friday 06-28 | 11:40 - 12:00
It has been proposed by Lilly et  al. (2021, 2024) that the activity of centaurs is due to a recent and rapid decrease in their semimajor axes dubbed “a-jumps”. Integrating the orbits of centaurs back in time, these authors show that these jumps are followed by rapid decrease in eccentricity, presenting the combination as the precursor to the activation of centaurs. The fact that the activity of centaurs depends on their orbital motion strongly implies that it also depends on the centaurs' dynamical history. However, that history cannot be known because strong interactions with giant planets render the orbits of the objects in that region chaotic. Also, the Lyapunov time of these objects cluster around 50 to 150 years, meaning that any efforts in determining their past history may at best be valid for a very short time. These uncertainties have cast doubt on the validity of the results reported by Lilly et al. (2021, 2024) and have raised the following questions: Are the a-jumps real, meaning that they are due to some underlying physics that affects only objects from a specific region of the parameter space, or are they the artifacts of N-body integration? To address these questions, we carried out a detailed analysis of the dynamical evolution of all centaurs and a large number of their clones. Results show that although at short times, rapid drops in semimajor axis may occur, when integrations are continued, the orbits of these object show a variety of random behaviors in the (a,e) space. We find that results of Lilly et al. (2024) are inconsistent with the statistics obtained from our integrations and that no correlation seems to exist between the activity of centaurs and the reported a-jumps. We present the details of our study and discuss the implications of its results.
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