Detectability of planetesimal impacts on giant exoplanets.

The detectability of planetesimal impacts on imaged exoplanets can be measured using Jupiter during the 1994 comet Shoemaker-Levy 9 events as a proxy. By integrating the whole planet flux with and without impact spots, the effect of the impacts at wavelengths from 2 to 4 μ m is revealed. Jupiter’s reflected light spectrum in the near-infrared is dominated by its methane opacity including a deep band at 2.3 μ m. After the impact, sunlight that would have normally been absorbed by the large amount of methane in Jupiter’s atmosphere was instead reflected by the cometary material from the impacts. As a result, at 2.3 μ m, where the planet would normally have low reflectivity, it brightened substantially and stayed brighter for at least a month. [ABSTRACT FROM AUTHOR]