The exoplanet 55 Cancri e, a super-Earth located 41 light-years away, has been found to host a hydrogen-rich, actively changing atmosphere. This discovery, based on observations from the James Webb Space Telescope, marks a significant step in understanding how planets orbiting extremely close to their host stars can retain and evolve atmospheres.
55 Cancri e orbits its star at a blistering distance of just 0.015 astronomical units, completing a full revolution in 18 hours. Surface temperatures soar to over 2,000 degrees Celsius, likely keeping much of its surface molten as a global lava ocean. The detection of atmospheric hydrogen suggests a thin, volatile envelope that is being continuously replenished, possibly by volcanic outgassing from the planet's interior.
The research team used JWST's NIRSpec instrument to capture transmission spectra during two transits in 2023, revealing spectral signatures of hydrogen and hints of carbon monoxide. These findings challenge previous models that predicted such close-in planets would have their atmospheres stripped away by stellar radiation. The active nature of the atmosphere implies a dynamic cycle of loss and replenishment. "This planet is a laboratory for extreme planetary physics," the study's lead author said. The composition of its atmosphere provides clues about the planet's interior, suggesting it may be geologically active. This bolsters the case that some lava worlds can sustain atmospheres, expanding the definition of habitable zones to include planets with exotic, high-temperature environments. The discovery has implications for the search for life beyond Earth, as it demonstrates that atmospheres can persist under conditions once thought impossible. It also underscores the value of JWST in characterizing exoplanet atmospheres, paving the way for more detailed studies of cooler, potentially habitable worlds. However, the planet's extreme heat and lack of liquid water render it uninhabitable by known standards.