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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

An artist's illustration pictures a cloudy red planet orbiting a distant red star. Near the exoplanet is a moon. Please see the explanation for more detailed information.

Methane Discovered on Distant Exoplanet

Explanation: 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.

Date September 20, 2023
Credit Illustration Credit: Ahmad Jabakenji ( ASU Lebanon , North Star Space Art ); Data: NASA , ESA , CSA , JWST
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
A service of: ASD at NASA / GSFC,
NASA Science Activation & Michigan Tech. U.