Voyager 1’s famous image of the ‘pale blue dot’ that is our world.
Can we use color information from direct images of exoplanets to learn which are most likely to house life?
Credit: NASA.

Colors of a Living World


Gliese 581d seems more and more to be considered a habitable zone planet, as Siddharth Hegde (Max Planck Institute for Astronomy) and Lisa Kaltenegger (Harvard-Smithsonian Center for Astrophysics) describe it in a new paper. They’re homing in on how to characterize a rocky exoplanet and point to HD 85512b and Gliese 667Cc as well as Gl581d as examples, but they also assume that we’ll be seeing more and more habitable zone worlds as the Kepler mission continues its work, so how we learn more about these planets becomes a big issue.

In the absence of missions like Terrestrial Planet Finder or ESA’s Darwin, which would allow us to analyze an exoplanetary atmosphere for biomarkers, what else can we do to find the places where life exists? Hegde and Kaltenegger look hard at a planet’s color to find the answer. Specifically, they’re interested in what’s known as a color-color diagram, which takes advantage of the fact that an object can be observed at a variety of wavelengths, with a different brightness becoming apparent in each band observed. ‘Color’ in this sense refers to the difference in brightness between different bands, easily plotted on a color-color diagram.

Read more: Colors of a Living World — Centauri Dreams.

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