Habitability of Larger-Than-Earth Planets
While there has been a lot of improvement in the methods and techniques used to search for exoplanets that may be habitable for life, the most popular and successful techniques favor the discovery of larger-than-Earth planets. This is because most of these methods rely on gravitational interactions or electromagnetic radiation interactions, both affected by mass and size of the planet. One example is transit detection, which relies on the size of the planet blocking out a substantial enough amount of light from the system star. Another example is Doppler shift detection, which counts on the mass of the planet being great enough to have a noticeable effect on the position of the system star, periodically altering its light’s Doppler shift. A few exoplanets have even been directly imaged now, the most recent one being a couple weeks or so ago.
However, the possibilities of many of the 331 detected exoplanets being habitable remains low, mostly due to these and accompanying characteristics. A new hypothesis paper by Bloh W. et al (nice names, source at bottom), suggests there is a much greater probability than previously thought. In their astrobiology paper they propose a thermal evolution model based on a star similar to the Sun and a planet with 10 times Earth mass.
Their model describes the photosynthetic biomass production (PBP) for the planet from a main sequence star like the Sun that becomes a red giant in its later life. They examined biogeochemical, geodynamical, and climatological processes that contribute to PBP. In particular, they paid special attention to all carbon processes, like the carbon-silicate one that is so important to homeostasis on Earth. They make extensive use of previous models, with slight modifications.
They found, like some other previous models, that planetary characteristics like overall continental area were the most important factors in habitability and PBP. Bloh et al state, “Habitability was found most likely for water worlds.” This is apparently the case for both pre red giant and red giant Sun like stars. For stars with a mass greater than that of the Sun, they found that the evolution will occur more rapidly, resulting in stricter temporal and spatial constraints on habitability, especially in the red giant phase.
Personally, I’m pretty hopeful for the widespread existence of life throughout the Universe. This paper puts together a good comprehensive model with conclusions that lean toward my hope. Check out the paper below, on arXiv.
Source:
Bloh W., Cuntz M., Schroder K.P., Bounama C., Fracnk S. Habitability of Super-Earth Planets around Other Suns: Models including Red Giant Branch Evolution. arXiv.org 12/4/08.
This entry was posted on Monday, December 8th, 2008 at 5:10 pm and is filed under Astrophysics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
