Exocomets in the Proxima Centauri system and their importance for water transport

Abstract

The scenario and efficiency of water transport by icy asteroids and comets are still amongst the most important unresolved questions of planetary systems. A better understanding of cometary dynamics in extrasolar systems shall provide information about cometary reservoirs and give an insight into water transport especially to planets in the habitable zone. The detection of Proxima Centauri-b (PCb), which moves in the habitable zone of this system, triggered a debate whether or not this planet can be habitable. In this work, we focus on the stability of an additional planet in the system and on water transport by minor bodies. We perform numerous N-body simulations with PCb and an outer Oort-cloud like reservoir of comets. We investigate close encounters and collisions with the planet, which are important for the transport of water. Observers found hints for a second planet with a period longer than 60 days. Our dynamical studies show that two planets in this system are stable even for a more massive second planet (∼ 12 Earth masses). Furthermore, we perform simulations including exocomets, a second planet, and the influence of the binary Alpha Centauri. The studies on the dynamics of exocomets reveal that the outer limit for water transport is around 200 au. In addition we show that water transport would be possible from a close-in planetesimal cloud (1-4 au). From our simulations, based on typical M-star protoplanetary disks, we estimate the water mass delivered to the planets up to 51 Earth oceans.

GJ 273: on the formation, dynamical evolution, and habitability of a planetary system hosted by an M dwarf at 3.75 parsec

“…But this study would be highly interesting due to the location of GJ 273b in between two minor-body reservoirs. An example of this are the theoretical studies of three systems HD 10180, 47 UMa, and HD 141399 by Dvorak et al (2020), where the authors studied the dynamical evolution of hypothetical exocomet populations, and the study presented by Schwarz et al (2017), where the authors explored the water delivery to the planet Proxima Centauri-b in consideration of a hypothetical population of exocomets. A similar study was performed by Dencs et al (2019), where the authors investigated a synthetic late-heavy-bombardment-like event in the TRAPPIST-1 system, which could have transported a significant amount of water to the habitable planets discovered in the system.…”

GJ 273: On the formation, dynamical evolution and habitability of a planetary system hosted by an M dwarf at 3.75 parsec

“…But this study would be highly interesting due to the location of GJ 273b in between two minorbody reservoirs. An example of this are the theoretical studies of three systems HD 10180, 47 UMa, and HD 141399 by Dvorak et al (2020), where the authors studied the dynamical evolution of hypothetical exocomet populations, and the study presented by Schwarz et al (2017), where the authors explored the water delivery to the planet Proxima Centauri-b in consideration of a hypothetical population of exocomets. A similar study was performed by Dencs et al (2019), where the authors investigated a synthetic late-heavy-bombardment-like event in the TRAPPIST-1 system, which could have transported a significant amount of water to the habitable planets discovered in the system.…”

Enrichment of the HR 8799 planets by minor bodies and dust

“…Since the range of the volatile fraction is rather wide we adopted an average value of 0.5 as the f vol for the HR 8799 outer belt. The same value was adopted by Ciesla et al (2015) and Schwarz et al (2018) in their studies of volatile delivery.…”