Tucked between a boiled-away desert and a giant snowball, an alien world called TRAPPIST-1e may be the only habitable planet in a newly discovered batch of seven, according to a new climate model.
When researchers announced the discovery of seven planets that closely orbit the cool red star TRAPPIST-1 in February, there was a rush to learn more about the little rocky worlds and find out if any might be habitable. One of the first scientists to model the worlds' potential climates in depth was Eric Wolf, a researcher at University of Colorado, Boulder. His model, along with others still to come, will paint a clearer picture of what the system's planets could actually be like.
Wolf modeled three planets around TRAPPIST-1 and tested different potential atmospheres to see whether any let liquid water exist on a planet's surface. He found that, in his simulation, only one of the planets listed as potentially habitable would be able to keep liquid water. [Exoplanet Tour: Meet the 7 Earth-Size Planets of TRAPPIST-1]
Snowballs and runaways
In particular, Wolf investigated planets d, e and f around TRAPPIST-1, which lies about 39 light-years from Earth. He found that planet d orbits too close to its star, building up a thick atmosphere of water vapor that heats the planet even further and boils the rest of the water off — a runaway greenhouse effect that guarantees the planet winds up too hot and dry to host life over time. Planet f, by contrast, is too far from its star, making it a snowball; any surface water would be frozen solid, and in the model, no combination of gases in the planet's atmosphere seemed to keep it warm enough, Wolf said.
"So that leaves us with planet e as the one real chance of having a temperate, habitable, Earth-like climate," Wolf told Space.com.
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