Methane Discovered on Distant Exoplanet

Where else might life exist? One of humanity’s great outstanding questions, locating planets where extrasolar life might survive took a step forward in 2019 with the discovery of a significant amount of water vapor in the atmosphere of distant exoplanet K2-18b. The planet and its parent star, K2-18, lie about 124 light years away toward the constellation of the Lion ( Leo ). The exoplanet is significantly larger and more massive than our Earth, but orbits in the habitable zone of its home star. K2-18, although more red than our Sun, shines in K2-18b ‘s sky with a brightness similar to the Sun in Earth’s sky. The 2019 discovery of atmospheric water was made in data from three space telescopes: Hubble, Spitzer, and Kepler, by noting the absorption of water-vapor colors when the planet moved in front of the star. Now in 2023, further observations by the Webb Space Telescope in infrared light have uncovered evidence of other life-indicating molecules — including methane. The featured illustration imagines exoplanet K2-18b on the far right orbited by a moon (center), which together orbit a red dwarf star depicted on the lower left.