For the first time ever, scientists have spotted an atmosphere clinging to a rocky planet where temperatures might allow liquid water to pool on its surface — a place that could theoretically harbor life. The planet, called LHS 1140 b, sits 48 light-years away in the constellation Cetus, and researchers say it has held onto this blanket of gases for more than three billion years. The discovery, published in the journal Science, marks a turning point in humanity's search for worlds beyond our solar system that might look and feel something like our own.
Scientists have found thousands of planets orbiting other stars, including some rocky ones in the so-called habitable zone — the just-right distance from a star where water wouldn't freeze or boil away. But figuring out whether those worlds actually had air wrapped around them had never been done until now. Collin Cherubim, who recently earned his PhD in Earth and Planetary Sciences from Harvard University, led the research. He didn't just guess the planet would have an atmosphere. He ran the numbers, predicted it, and then pointed a telescope at the right patch of sky to prove it.
The team used an instrument called the WINERED Spectrograph mounted on the Magellan Observatory in Chile. They watched as LHS 1140 b passed in front of its star, a cool red dwarf. When starlight filtered through the planet's upper atmosphere, the spectrograph picked up helium gas — hydrogen's chatty neighbor — streaming off into space. That helium was the giveaway. "An atmosphere is essential for a planet to support life as we know it," Cherubim said. "This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star."
His advisor, David Charbonneau of Harvard, admitted he was skeptical at first. "Collin analyzed the planets we knew about and predicted that this one would have a helium atmosphere," Charbonneau said. "Then he organized telescope time, got the data, and the detection was statistically rock-solid." Another advisor, Robin Wordsworth, who helped guide the research, reflected on how far the field has come. "Twenty years ago we wondered whether other terrestrial-type planets even existed," he said. "Then we learned they're common, and found some in the habitable zone. The next question was whether any of them had managed to keep an atmosphere. Now we know at least one has."
LHS 1140 b's atmosphere has apparently endured for more than three billion years — longer than life has existed on Earth. That longevity makes it a prime candidate for follow-up studies. Cherubim wants to dig deeper, learning what else lives in that atmosphere and whether the planet might have oceans or other ingredients for life. He also plans to use his model to hunt for more worlds like it. "This has been a model validation," he said, "and hopefully it's just the first of many more observations to come."