Detectability of Planetesimal Impacts on Giant Exoplanets

TL;DR

This study uses Jupiter's 1994 comet impact as a proxy to assess how detectable planetesimal impacts on giant exoplanets might be through near-infrared observations, revealing impact signatures in reflected light spectra.

Contribution

It demonstrates how impact events can alter the reflected light spectrum of giant planets, providing a method to detect such impacts on exoplanets using near-infrared observations.

Findings

Impact spots increase brightness at 2.3 microns for at least a month.

Impacts cause significant spectral changes in the planet's reflected light.

Impact detection is feasible through spectral analysis in the 2-4 micron range.

Abstract

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 - 4 microns is revealed. Jupiter's reflected light spectrum in the near-infrared is dominated by its methane opacity including a deep band at 2.3 microns. 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 microns, where the planet would normally have low reflectivity, it brightened substantially and stayed brighter for at least a month.