Exoplanet may reveal secrets about the edge of habitability

How close can a rocky planet be to a star, and still sustain water and life? (by James Dean, Cornell Chronicle)

A recently discovered exoplanet may be key to solving that mystery, providing important insights about conditions at the inner edge of a star’s habitable zone and why Earth and Venus developed so differently, according to new research led by Lisa Kaltenegger, director of the Carl Sagan Institute and associate professor of astronomy in the College of Arts and Sciences (A&S).

Kaltenegger’s team found that the “super-Earth” LP 890-9c (also named SPECULOOS-2c), which orbits close to the inner edge of its solar system’s habitable zone, would look very different depending on whether it still had warm oceans, a steam atmosphere or if it had lost its water, assuming it once had oceans like Earth’s.

“Looking at this planet will tell us what’s happening on this inner edge of the habitable zone – how long a rocky planet can maintain habitability when it starts to get hot,” Kaltenegger said. “It will teach us something fundamental about how rocky planets evolve with increasing starlight, and about what will one day happen to us and Earth.”

Kaltenegger is the lead author of “Hot Earth or Young Venus? A Nearby Transiting Rocky Planet Mystery,” published June 21 in Monthly Notices of the Royal Astronomical Society: Letters. Co-authors are Rebecca Payne, research associate in the Department of Astronomy (A&S); Zifan Lin ’20, doctoral student at the Massachusetts Institute of Technology; James Kasting, professor emeritus at Pennsylvania State University; and Laetitia Delrez, postdoctoral researcher at the University of Liège in Belgium, who led an international team that reported the discovery of LP 890-9c in September 2022.

“We don’t know what this planet on the edge of habitability could be like, so we have to look,” she said. “This is what real exploration is about.”