Chthonian planet

Artist's conception of COROT-7b.

Artist's conception of HD 209458 b transiting its star.

A chthonian planet ( /ˈkθoʊniən/, sometimes misspelled 'cthonian') is a hypothetical class of celestial objects resulting from the stripping away of a gas giant's hydrogen and helium atmosphere and outer layers, which is called hydrodynamic escape. Such atmospheric stripping is a likely result of proximity to a star. The remaining rocky or metallic core would resemble a terrestrial planet in many respects.^[1]

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.

COROT-7 b may be the first chthonian planet discovered.^[2][3] Kepler-10b is also the second chthonian planet found.

Chthonia (from Greek: χθων) means "of the Earth". The term was coined by Hébrard et al., since the term chthonian generally refers to Greek deities from the infernal underground.

See also

• Hot Jupiter
• COROT-7b: diameter 1.7 x Earth, mass 4.8 x Earth, orbital period = 20.5 hours^[4] (super-Earth candidate)
• Hypothetical planet

References

1. ^ Hébrard G., Lecavelier Des Étangs A., Vidal-Madjar A., Désert J.-M., Ferlet R. (2003), Evaporation Rate of Hot Jupiters and Formation of chthonian Planets, Extrasolar Planets: Today and Tomorrow, ASP Conference Proceedings, Vol. 321, held 30 June - 4 July 2003, Institut d'astrophysique de Paris, France. Edited by Jean-Philippe Beaulieu, Alain Lecavelier des Étangs and Caroline Terquem.
2. ^ "Exoplanets Exposed to the Core". AstroBiology Magazine. 2009-04-25. http://www.astrobio.net/index.php?option=com_news&task=detail&id=3105. Retrieved 2009-07-13. 
3. ^ "Super-Earth 'began as gas giant'". BBC News. 10 January 2010. http://news.bbc.co.uk/1/hi/sci/tech/8446125.stm. Retrieved 2010-01-10. 
4. ^ "Planet : CoRoT-7 b". http://exoplanet.eu/planet.php?p1=CoRoT-7&p2=b. Retrieved 2009-06-13.