Enrichment of the HR 8799 planets by minor bodies and dust

Abstract

In the Solar System, minor bodies and dust deliver various materials to planetary surfaces. Several exoplanetary systems are known to host inner and outer belts, analogues of the main asteroid belt and the Kuiper belt. We study the possibility that exominor bodies and exodust deliver volatiles and refractories to the exoplanets in the system HR8799 by performing N-body simulations. The model consists of the host star, four giant planets (HR8799 e, d, c, and b), 650000 test particles representing the inner belt, and 1450000 test particles representing the outer belt. Moreover we modelled dust populations that originate from both belts. Within a million years, the two belts evolve towards the expected dynamical structure (also derived in other works), where mean-motion resonances with the planets carve the analogues of Kirkwood gaps. We find that, after this point, the planets suffer impacts by objects from the inner and outer belt at rates that are essentially constant with time, while dust populations do not contribute significantly to the delivery process. We convert the impact rates to volatile and refractory delivery rates using our best estimates of the total mass contained in the belts and their volatile and refractory content. Over their lifetime, the four giant planets receive between $10^{-4}$ and $10^{-3}M_\bigoplus$ of material from both belts. The total amount of delivered volatiles and refractories, ${5\times10^{-3}\textrm{M}_\bigoplus}$, is small compared to the total mass of the planets, $11\times10^{3}\textrm{M}_\bigoplus$. However, if the planets were formed to be volatile-rich, their exogenous enrichment in refractory material may well be significant and observable, for example with JWST-MIRI. If terrestrial planets exist within the snow line of the system, volatile delivery would be an important astrobiological mechanism and may be observable as atmospheric trace gases.

11 pages, 8 figures, accepted for publication in Astronomy&Astrophysics

References in corpus (9)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• Hybrid Symplectic Integrators for Planetary Dynamics
• Herschel images of Fomalhaut. An extrasolar Kuiper Belt at the height of its dynamical activity
• Volatile Delivery to Planets from Water-rich Planetesimals around Low Mass Stars
• Long-term stability of the HR 8799 planetary system without resonant lock
• Asteroid impacts on terrestrial planets: The effects of super-Earths and the role of the ${\nu }_6$ resonance
• Modelling the Inner Debris Disc of HR 8799
• Shaping HR8799's outer dust belt with an unseen planet
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Cited by in corpus (1)

• The First Dynamical Mass Measurement in the HR 8799 System