Is there any­body OUT THERE?

If life does ex­ist on ex­o­plan­ets, its fin­ger­prints could be dis­cov­ered in the light from dis­tant stars

Sky at Night Magazine - - EXOPLANET HUNTING -

It’s the mil­lion-dol­lar ques­tion that as­tronomers – and bi­ol­o­gists – are try­ing to an­swer. We now know that plan­ets are plen­ti­ful and that the sim­ple car­bon-bear­ing build­ing blocks of life can be found all across in­ter­stel­lar space. But so far, Earth is the only planet known to har­bour liv­ing or­gan­isms. And al­though many ex­o­plan­ets or­bit in the hab­it­able zone of their par­ent stars, be­ing hab­it­able isn’t quite the same as be­ing in­hab­ited.

Dur­ing a tran­sit, how­ever, a tiny amount of starlight passes through the planet’s at­mos­phere be­fore reach­ing Earth. At­mo­spheric mol­e­cules leave tell­tale spec­tro­scopic ‘fin­ger­prints’ in the light of the par­ent star, mainly at in­frared wave­lengths. Fu­ture gi­ant ground-based tele­scopes, as well as NASA’s James Webb Space Tele­scope (JWST), due to launch in the spring of 2019, will be able to de­tect th­ese so-called biomark­ers – chem­i­cal com­pounds such as oxy­gen, ozone and meth­ane – that are most likely to be pro­duced by bi­o­log­i­cal ac­tiv­ity on the planet’s sur­face.

“TESS will de­liver the ob­ser­va­tional tar­gets for JWST,” says Dr Elisa Quin­tana of NASA’s God­dard Space Flight Cen­ter. Whether the mil­lion-dol­lar ques­tion will be an­swered any time soon, how­ever, is any­body’s guess.

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