This really is the age of planet-hunting. The number of confirmed exoplanets now exceeds 800, and there are more than 2,700 other candidates waiting for entry into the hall of fame. When you consider how far away some of these suckers are, it really is astounding.
Up until now we have been able to get estimates of orbit, general size and mass. Combined with knowledge of star type, this has enabled astronomers to place the exoplanets in relation to the ‘Goldilocks’ or habitable zone, where liquid water is possible (seen as a likely precursor for the development of life (as we know it, Jim)).
Now the analysis of these targeted systems has gone to the next level. Astronomers are beginning to install infrared cameras on ground-based telescopes equipped with spectrographs. This will enable tell-tale signatures of key molecules to be detected. One key feature of this work is figuring out ways of blocking the glare of the planet’s adjacent star. NASAs planned James Webb Space Telescope will also use a similar strategy to study the atmospheres of planets a little bit bigger than Earth.
Two factors can improve the view. Young planets have more heat left over from their formation, increasing the infrared signal for the spectrographs. The other approach is to look at planets further out from their stars, helping to isolate their spectra from the star’s light. Of course looking that far out means starting with Jupiter-sized planets, but astronomers hope to be able to refine their technique to allow the atmospheric compositions of smaller – and older –planets to be examined.
The Holy Grail is finding an Earth-sized planet in the habitable zone with molecules that indicate the probable presence of life. We might have to wait for the proposed Terrestrial Planet Finder before we can crack this.
Still, it’s pretty exciting stuff!