There is a group of hypothetical planets known as Chthonian Planets that are thought to occur when a star strips a gas giant of its atmosphere leaving behind the core (Hebrard et al., 2003). This process is often hypothesized about by using Hot Jupiters which are within close proximity to their host star. This causes hydrogen particles to heat up, gain energy, and escape into the atmosphere. (Hebrard, et al., 2003). The resulting core left behind appears similar to a rocky planet like Mars or a metallic planet like Mercury.
The rate the hydrogen particles are escaping from the gas giant’s is influenced by the temperature of the planet and velocity of the particles (Hebrard, 2003). It is believed this rate is not substantial since most Hot Jupiters with evaporating atmospheres have existed in their conditions for at least 1 billion years (Lecavelier des Etangs, A., 2006). It has been calculated the Hot Jupiters of critical mass should evaporate and leave behind a rocky core after roughly 5 billion years and larger planets will have longer lifespans and less noticeable changes over time that would be caused by the evaporation (Barrafe, I. et al, 2004).
Bibliography
Hebrard, G., A. Lecavelier des Etangs, A. Vidal-Madjar, J.-M. Desert &
R. Ferlet. (Dec 2003). Evaporation rate of hot Jupiters and formation of
Chthonian planets. ArXiv. https://doi.org/10.48550/arXiv.astro-ph/0312384
Barrafe, I., F. Selsis, G. Chabrier, T. S. Barman, F. Allard, P.H. Hauschildt & H. Lammer. (May 2004). The effect of evaporation on the evolution of close-in giant planets. A&A, 419(2), L13 – L16. https://doi.org/10.1051/0004-6361:20040129
Chthonian planet. (Feb 2022). Wikipedia. Retrieved Mar 24, 2022 https://en.wikipedia.org/wiki/Chthonian_planet
Lecavelier des Etangs, A. (Sep 2006). A diagram to determine the evaporation status of extrasolar planets. A&A, 461(3), 1185 – 1193. https://doi.org/10.1051/0004-6361:20065014
Mysteries of Space 