Dust Accretion onto Exoplanets

Abstract

Accretion of interplanetary dust onto gas giant exoplanets is considered. Poynting–Robertson drag causes dust particles from distant reservoirs to slowly inspiral toward the star. Orbital simulations for the three-body system of the star, planet, and dust particle show that a significant fraction of the dust may accrete onto massive planets in close orbits. The deceleration of the supersonic dust in the planet’s atmosphere is modeled, including ablation by thermal evaporation and sputtering. The fraction of the accreted dust mass deposited as gas-phase atoms is found to be large for close-in orbits and massive planets. If mass outflow and vertical mixing are sufficiently weak, the accreted dust produces a constant mixing ratio of atoms and remnant dust grains below the stopping layer. When vertical mixing is included along with settling, the solutions interpolate between the mixing ratio due to the meteoric source above the homopause, and that of the well-mixed deeper atmosphere below the homopause. The line opacity from atoms and continuum opacity from remnant dust may be observable in transmission spectra for sufficiently large dust accretion rates, a grain size distribution tilted toward the blowout size, and sufficiently weak vertical mixing. If mixing is strong, the meteoric source may still act to augment heavy elements mixed up from the deep atmosphere as well as provide nucleation sites for the formation of larger particles. The possible role of the Lorentz drag force in limiting the flow speeds and mixing coefficient for pressures ≲1 mbar is discussed.

A JWST Survey for Planetary Mass Brown Dwarfs in IC 348*

“…Therefore, a second scenario could involve the hydrocarbons originating in disks around the brown dwarfs and surviving accretion onto the photospheres. Recent studies have considered analogous situations in which young planetary companions accrete dust from the debris disks around their parent stars (Arras et al 2022) and their spectra are affected by the accreted dust (Madurowicz et al 2023). One final possibility is that sources 1 and 3 are ejected planets and their hydrocarbon features are related to their formation process in circumstellar disks.…”

The Infrared Colors of 51 Eridani b: Micrometeoroid Dust or Chemical Disequilibrium?

“…Extremely young protoplanets appear bright in Hα in the ultraviolet due to ongoing accretion in the protoplanetary disk (Zhou et al 2021). The possibility that interplanetary or circumstellar dust captured by exoplanets could modify their spectra has recently been investigated (Arras et al 2022) in the context of transiting planets. Since systems that host debris disks are much more likely to host planets than those without (Marshall et al 2014;Meshkat et al 2017), considering the interactions between planets and disk material is important.…”