Volume 638, June 2020
|Number of page(s)||11|
|Section||Planets and planetary systems|
|Published online||10 June 2020|
Enrichment of the HR 8799 planets by minor bodies and dust
Kapteyn Astronomical Institute, University of Groningen,
2 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands
3 NOVA Netherlands Research School for Astronomy, The Netherlands
4 Leiden Observatory, Leiden University, Leiden, The Netherlands
5 Department of Physics, The Catholic University of America, Washington, DC 20064, USA
6 Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
7 Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands
Accepted: 12 May 2020
Context. 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, respectively.
Aims. We study the possibility that exominor bodies and exodust deliver volatiles and refractories to the exoplanets in the well-characterised system HR 8799.
Methods. We performed N-body simulations to study the impact rates of minor bodies in the system HR 8799. The model consists of the host star, four giant planets (HR 8799 e, d, c, and b), 650 000 test particles representing the inner belt, and 1 450 000 test particles representing the outer belt. Moreover we modelled dust populations that originate from both belts.
Results. 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⊕ of material from both belts.
Conclusions. The total amount of delivered volatiles and refractories, 5 × 10−3 M⊕, is small compared to the total mass of the planets, 11 × 103 M⊕. 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.
Key words: planets and satellites: general / comets: general / minor planets, asteroids: general / methods: numerical / astrobiology
© ESO 2020
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.