In this thesis we study the fate of large bodies (planetesimals, asteroids) that impact into the atmosphere of a forming extrasolar giant planet. We study how they loose their mass and energy while they fly into the denser parts of the gaseous envelope. This is similar to atmospheric impacts into Earth like the Chelyabinsk meteor in 2013 or the impact of comet Shoemaker Levy 9 into Jupiter in 1994. We then study how the planet itself reacts to this massive impact, including the possible formation of an impact plume (similar to an "Atompilz"). Finally we investigate whether these impact flashes could be detected from Earth.
Dash cam videos of the Chelyabinsk meteor