By Lee Billings
Imagine stepping into a time machine, one that could traverse not only billions of years but also countless light years of space, all in search of life in the universe. Where would you find most of it, and what would it look like? The answer—or at least scientists’ best guess—might surprise you.
You might think most life out there would be like what we see on Earth today: grasses, trees and frolicking animals all orbiting yellow stars on watery worlds under blue, oxygen-rich skies. But you would be wrong. Astronomers conducting a galactic census of planets in the Milky Way now suspect most of the universe’s habitable real estate exists on worlds orbiting red dwarf stars, which are smaller but far more numerous than stars like our Sun. In part because of their immense numbers, such stars are in some respects easier for astronomers to study. Consider, for instance, the red dwarf star called TRAPPIST-1, just under 40 light-years away. In 2017 astronomers discovered it is orbited by at least seven temperate Earth-size planets. A plethora of new observatories—chief among them NASA’s multi-billion-dollar James Webb Space Telescope, slated to launch in 2019—could soon begin studying the planets of TRAPPIST-1 and other nearby red-dwarf planets for signs of habitability and life.
In the meantime, no one really knows, of course, what you would see if you visited one of these strange worlds in your planet-hopping time machine, but if they are at all like Earth, chances are you would find a planet dominated by microbes rather than charismatic megafauna. A new study published in the January 24 edition of Science Advances explores what this curious fact might mean for alien-hunting astronomers. Co-authored by David Catling, an atmospheric chemist at the University of Washington in Seattle, the study peers deep into our planet’s history to devise a novel recipe for finding single-celled life on faraway worlds in the not-too-distant future.
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