The discovery of helium escaping from the atmosphere of LHS 1140b, a rocky exoplanet in the habitable zone of its star, is a significant breakthrough in our understanding of exoplanet atmospheres. This finding, published in the journal Science, reveals a dynamic and complex atmosphere that may be crucial for the planet's habitability. The planet, orbiting a 3-billion-year-old inactive M-dwarf star, is 39 light-years away in the constellation of Cetus. It has a mass of 5.6 Earth masses and a radius of 1.73 Earth radii, with an orbital period of 24.7 days and an equilibrium temperature of 226 K (minus 47 degrees Celsius, or minus 53 degrees Fahrenheit).
The discovery was made possible by the use of the Warm Infrared Echelle Spectrograph to Realize Extreme Dispersion (WINERED) on the Magellan Clay telescope at Las Campanas Observatory. Astronomers observed LHS 1140b in 2024 and saw evidence of helium escaping from its atmosphere, attributed to heating from stellar X-rays and extreme ultraviolet radiation. However, 2025 observations revealed no escaping helium, suggesting that the atmospheric escape is variable.
The researchers interpreted these results to indicate the presence of a highly layered atmosphere, with a helium-dominated and hydrogen-poor upper atmosphere and other chemical species like water trapped at lower altitudes. This finding raises questions about the planet's habitability and the nature of its atmosphere. Is it a bare rock with no atmosphere that occasionally burps up gas that escapes immediately, or is there a steady-state atmosphere that leaks out substances like Earth does from time to time?
The discovery of helium escaping from LHS 1140b is a significant step forward in our understanding of exoplanet atmospheres and their potential for supporting life. It highlights the importance of continued observation and research in this field, as we strive to answer the question of whether life exists beyond Earth.
