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Astrobiology - Exoplanets

Exoplanets as a subject is covered in the exoplanets section. Exoplanets in terms of astrobiology does have implication on another project: SETI. While I personally believe in the SETI project, it is easy to see that this subject does garner some hostile feeling. My wife used to work in the same building as SETI's home office, and bomb threats were a common occurrence.

While there is no dedicated SETI section on this site, the Additional Resources provides, well, Additional Resources.

Detection of exoplanets has benefited SETI such that targeted searches can be performed. In order to help narrow the target list, space-based interferometers like the IRSI (InfraRed Space Interferometer - Project Darwin) and the TPF (Terrestrial Planet Finder) are in the design stages. The sensitivity of these instruments is expected to detect smaller planets as well as attempt a spectroscopic analysis of a planets atmosphere (if present). The specific spectroscopic signature of interest is (click for larger image):

Image Credit

The three main ingredients of a life-sustaining atmosphere are:

  • Water - H2O
  • Ozone - O3
  • Carbon Dioxide - CO2

Detection of this type of atmosphere is currently the Holy Grail of astronomy. Predicted launch dates for the TPF is 2014 and 2015 for the IRSI.

One of the things to consider when looking for Earth-like planets is determining the habitable zones.

(Image credit: Brooks/Cole Thomson Learning)

Depending on the type of star, the location of a planet is important because of concerns over heat. The temperature of the zone should be "just right," but that's a relative term. The image above serves as an example to what habitable zones may reside about different types of stars.

There are a lot of stars out there so the chances of an Earth-like planet existing around some other star are quite high, but how high exactly?

(Image credit: Brooks/Cole Thomson Learning)

Frances Drake, the astronomer who founded the SETI project, put together the Drake Equation to serve as a guide. This is not a real mathematical equation, but instead gets us to think that the possibilities of extra-terrestrial life is greater than we realize.


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