A climate model for exoplanets

A climate model with the aim of determining which planets outside our solar system may have characteristics similar to those of terrestrial habitability, or liquid water. And ‘ the aim of a study conducted by researchers at INAF – Astronomical Observatory of Trieste and IASC – NRC, the results of which are published in the Astrophysical Journal.



A group of researchers INAF – Astronomical Observatory of Trieste and the Institute of Atmospheric Sciences and Climate of the National Research Council (IASC – NRC) of Turin had developed a climate model to energy balance (Ebm) with the purpose of determining which planets outside our solar system may have characteristics similar to those of habitability terrestrial , or water in the liquid state , as a function of atmospheric pressure, carbon dioxide concentration in the atmosphere , the characteristics of the orbit (eccentricity , inclination of the axis of rotation ) and the period of rotation. The results of this first study are published in the Astrophysical Journal.

“Basically, the search for life – says Giuseppe Murante, INAF- Astronomical Observatory of Trieste – must relate to places where life can exist, can be developed for a variety of reasons physic-chemical and biophysical, where liquid water is present. What we did was to create models of the atmosphere that are applicable to extrasolar planets so as to see whether the presence of an atmosphere can vary the circumstellar habitable zone.”

To be clear, it makes the comparison with the planets of our system in order to have a model specifying the range of habitability of other stars? “It is not exactly that. On a planet that we know well, such as ours, there is a science like climatology using numerical techniques to study the climate. So we know that the atmosphere affects the surface temperature. If the Earth had no atmosphere the average surface temperature would be below zero, while it is about 15 degrees, thanks precisely to the fact that there is an atmosphere, that there is a greenhouse effect. What we did was to use climate models very simple, lacking the details that apply to the earth, such as geography, since we cannot know that for extrasolar planets, to see under what conditions, given a planet of a certain type, with a certain rotation speed, a certain distance from a certain kind of star, in the presence of various types of atmosphere if there might be the presence of liquid water on the surface. That is the surface temperature of the planet. In particular, we studied the effect of atmospheric pressure, and showed that the circumstellar habitable zone widens with increasing pressure and, in addition, at high pressures the planet’s surface temperature tends to become uniform, leveling differences seasonal and latitudinal.”

This model is being applied in the study of exoplanets?

“What we are doing at the moment is to apply it to some of extrasolar planets that are technically called super-earths, which are either in or near the habitable zones of their stars. There is, of course, an immediate effect ” observational ” of this work that is theoretical, rather than what the job can do to suggest that distance from a star of a certain type that you could hope to have a planet with liquid water, and then possibly with presence of life forms. We must also say that at the moment we have not the technological capabilities for the study of the atmospheres of extrasolar planets the size of the super-lands yet. There is no doubt; however, that this model can allow us to better choose between the extrasolar planets is worth more than what is worth mainly because it has more prerogatives habitability.

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