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 $\la 1\, \rm mbar$ is discussed.

28 pages, 23 figures

References in corpus (13)

• A gaseous metal disk around a white dwarf
• Transience of hot dust around sun-like stars
• Debris disks around Sun-like stars
• Foretellings of Ragnarök: World-engulfing Asymptotic Giants and the Inheritance of White Dwarfs
• Collisional processes and size distribution in spatially extended debris discs
• Transit Signatures of Inhomogeneous Clouds on Hot Jupiters: Insights From Microphysical Cloud Modeling
• A near-infrared interferometric survey of debris-disc stars. IV. An unbiased sample of 92 southern stars observed in H-band with VLTI/PIONIER
• Effects of Bulk Composition on The Atmospheric Dynamics on Close-in Exoplanets
• The Near-Sun Dust Environment: Initial Observations from Parker Solar Probe
• A Model of the H$\alpha$ and Na Transmission Spectrum of HD 189733b
• Polluted White Dwarfs: Mixing Regions and Diffusion Timescales
• Near-infrared emission from sublimating dust in collisionally active debris disks
• The nature of HHL 73 from optical imaging and Integral Field Spectroscopy

Cited by in corpus (3)

• The infrared colors of 51 Eridani b: micrometereoid dust or chemical disequilibrium?
• Size distribution of small grains in the inner zodiacal cloud
• Review and prospects of hot exozodiacal dust research for future exo-Earth direct imaging missions