Astronomers have detected helium escaping the atmosphere of exoplanet LHS 1140b, located about 50 light-years away. This observation, detailed in the journal Nature, provides clues about the planet's atmospheric composition.

LHS 1140b orbits a red dwarf star and receives significant radiation. The rate of helium loss, estimated at 100,000 kilograms per second, suggests that much of the planet's original hydrogen has already been depleted. The presence of escaping helium implies that heavier elements, such as oxygen, nitrogen, and molecules like water, are likely retained in the atmosphere.

This finding helps define the "cosmic shoreline" for this star system, indicating the boundary where a star's radiation is intense enough to strip away atmospheres. The researchers suggest that LHS 1140b has a helium-rich upper atmosphere with little remaining hydrogen, with a thicker, unknown atmosphere beneath.