In a major milestone in the search for life on other planets, astronomers have detected, for the first time, an atmosphere surrounding an Earth-like, rocky planet orbiting within the habitable zone of another star. The finding provides the strongest evidence yet that worlds with conditions similar to Earth in composition and temperature, with the potential to support life, could exist beyond our solar system.

"An atmosphere is essential for a planet to support life as we know it," said lead author Collin Cherubim, who recently earned his Ph.D. in Earth and Planetary Sciences from Harvard University.

"This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star."

Published in Science, the study reports observational results detecting helium escaping from the atmosphere of LHS 1140 b, a rocky exoplanet about 48 light-years from Earth. Motivated by theoretical predictions, the discovery provides evidence that the planet possesses an atmosphere.

The planet orbits a red dwarf star within the star's habitable zone, or the region where temperatures and environmental conditions are within the range that could support liquid water on the planet's surface.

Astronomers have discovered thousands of exoplanets, including a few rocky worlds within their stars' habitable zones, but determining whether those planets have atmospheres has remained a great challenge.