Sara Seager at the Massachusetts Institute of Technology reckons the Drake equation is ripe for a revamp. Her version narrows a few of the original terms to account for our new best bets of finding life, based in part on what Kepler has revealed. If the original Drake equation was a hatchet, the new Seager equation is a scalpel.
Red dwarfs are the most common stars in our galaxy: projections based on Kepler data suggest that the nearest habitable Earth-sized world could orbit a red dwarf as close as 6.5 light years away.
Even better, it will be easier to probe these planets for gases associated with life, because tighter orbits mean that more of the star’s light will filter through a planet’s atmosphere on the way to us, picking up telltale clues to its composition. Seager’s goal is to find the fraction of habitable Earth-sized worlds in our galactic neighbourhood with detectable atmospheric biosignatures – in other words, inhabited worlds. She has already put the number of inhabited planets that the James Webb space telescope might see at less than 10.
“Just like with the Drake equation, some of the terms are always speculative,” Seager says.
If Seager or someone else detected biosignatures, we would spend more time looking in those places for hints of intelligence, says Jill Tarter of the SETI Institute. “You’d know that’s an inhabited world, not just a habitable world. And then you can ask the question, did they develop any technology we might detect?”