| Maintainer | https://mastodon.social/@hannorein |
| REBOUND code | https://github.com/hannorein/rebound |
| Bot source code | https://github.com/hannorein/reboundcitationbot |
We investigate the dynamical evolution of particles in the $β$ Pic system to determine likely formation pathways to the present-day observed exocomet populations. We aim to relate these results to similar studies recently carried out since the discovery of the inner planet $β$ Pic c. We simulate the $β$ Pic system using the non-symplectic adaptive N-body integrator IAS15 in REBOUND. We seed the system with over 100,000 mass-less test particles that evolve for 25 Myr, and adopt initial conditions and a particle distribution that closely matches similar simulations in recent literature. Using IAS15, REBOUND resolves close-encounters between test particles and the two gas giants in the system, which is crucial for understanding aspects of the dynamical evolution. Planet-disk interactions rapidly clear most of the system within 35 AU apart from a region within the orbit of $β$ Pic c, and a region between 20 and 25 AU. After 10 Myr, exocomets can be sourced continuously from these regions, as well as from the inner edge of the region beyond ~35 AU where particles are stable on longer timescales. From the region interior to $β$ Pic c, the exocomets are formed by excitation via mean-motion resonance with $β$ Pic c, obtaining a narrow distribution of radial velocities, consistent with spectroscopic observations. Particles initialized in the outer system may enter onto stargrazing orbits due to disruption by the two gas giants, causing a wider radial velocity distribution, and we propose that this population corresponds to a second dynamical family previously observed via spectroscopy. These particles typically undergo chaotic dynamical evolution for $10^2$ to $10^3$ years after passing the water sublimation limit at ~8 AU until reaching the sublimation distance of calcium near 0.4 AU, implying that the two families of exocomets may have different volatile contents.
Imminent impactors are natural bodies discovered in space before impacting the Earth. They provide a rare opportunity to characterize individual near-Earth objects (NEOs) in great detail as asteroids in space, meteors in Earth's atmosphere and meteorites on the ground. The Vera C. Rubin Observatory's upcoming Legacy Survey of Space and Time (LSST) is expected to transform our understanding of the NEO population. In this work, we evaluate LSST's expected discovery performance for imminent impactors using $343$ meter-size objects previously recorded in NASA's CNEOS database as fireballs impacting Earth's atmosphere. We simulate pre-impact observations of these CNEOS impactors with the Sorcha survey simulator under LSST's default three-night discovery strategy and a one-night strategy for fast-moving objects that relies on matching aligned streaks in two exposures on the same night. We estimate that LSST will discover $\sim1-2$ meter-size and larger imminent impactors per year, representing $\sim4\%$ of all Earth impactors $\gtrsim1$ m in diameter and almost doubling the current discovery rate of imminent impactors. The median time of discovery and median time of first observation for impactors discovered in our simulations are $\sim1.57$ and $\sim3.06$ days before impact, respectively. The spatial distribution of the 11 previously discovered imminent impactors is biased towards the Northern Hemisphere, where the observatories that discovered them are located. We find a similar trend towards Southern Hemisphere impacts in our simulated LSST detections of the CNEOS impactors, suggesting Rubin will provide a powerful counterpart to existing asteroid surveys primarily located in the Northern Hemisphere.