derives from formed as result of causally downstream of or within stellar wind planet giant gas planet chthonian planet envoAstro cthonian planet This class is largely theoretical, however, some likely candidates exist. HD 209458 b and Gliese 436b are examples of a gas giants that are in the process of having their atmospheres stripped away. COROT-7b is the first exoplanet found that might be chthonian. A planet which is formed as a result of a gas giant's hydrogen and helium atmosphere, as well as its outer layers, being stripped away by a stellar wind through photoevaporation and hydrodynamic escape. photoevaporation hydrodynamic escape