chthonian planet

This as-yet hypothetical class of planets are called "Chthonian planets".

COROT-7b may be the first chthonian planet discovered, followed by Kepler-10b.

After their atmospheres and outer layers are stripped away (hydrodynamic escape), their cores may become chthonian planets.

The Uranus-mass planet may be a chthonian planet, the core of a gas giant which has had its outer layers stripped away by stellar radiation.

While many hot Jupiters have been found in the process of losing their atmospheres, as of 2008, no genuine Chthonian planets have been discovered.

Also, a class of hot Jupiters may exist called Chthonian planets, that orbit so close to their star that their atmospheres have been blown away completely by stellar radiation.

Theoretical work suggests that CoRoT-7b could be a chthonian planet (the remains of a Neptune-like planet from which much of the initial mass has been removed due to close proximity to its parent star).

HD 209458 b is an example of a planet that is in the process of having its atmosphere stripped away, though it is not itself a chthonian planet nor is it expected to become one in the near future.

Exoplanets that are extremely close to their star, such as hot Jupiters can experience significant hydrodynamic escape to the point that they cease to be gas giants and are left with just the core, at which point they would be called Chthonian planets.