HELIUM LOSS OBSERVED IN ATMOSPHERE OF DISTANT EXOPLANET

Researchers have detected helium being lost from the atmosphere of an exoplanet orbiting the star LHS 1140, located approximately 50 light-years away. The findings, published in Nature, allow scientists to infer details about the remaining composition of the planet's atmosphere based on the rate at which helium escapes. The exoplanet, designated LHS 1140c, orbits close to its host star, completing one orbit in just under four days and receiving roughly five times more radiation than Earth receives from the Sun.

LHS 1140a is a red dwarf star with two known planets in its system. A second planet, LHS 1140b, orbits considerably farther out, taking nearly 25 days per orbit and receiving less than half the light that Earth receives from the Sun. Despite this lower radiation exposure, theoretical calculations suggest the planet receives sufficient energy to sustain liquid water on its surface if that radiation were fully converted to heat. Astronomers have tracked LHS 1140b through its gravitational effects on the host star and by observing it transit across the star's face from Earth's perspective.

The detection of helium loss provides insight into planetary atmospheric evolution across billions of years. Originally, most planets are thought to possess hydrogen and helium-dominated atmospheres, but these gases can be lost to space or transformed through chemical reactions. The observation of active atmospheric loss from LHS 1140c demonstrates how stellar radiation and proximity to a star influence atmospheric retention on exoplanets, contributing to understanding of how planetary atmospheres change over time.