NASA's James Webb Space Telescope has identified a fourth exoplanet in the Kepler-51 star system, located approximately 2,615 light-years from Earth in the Cygnus constellation. Previously known for hosting three 'super-puff' exoplanets—Kepler-51b, Kepler-51c, and Kepler-51d—this new discovery adds to the intriguing characteristics of this planetary system.
The Kepler-51 planets, first detected by NASA's Kepler Space Telescope in 2012, exhibit an orbital period ratio of 1:2:3, corresponding to approximately 45, 85, and 130 days respectively. These planets are significantly more massive than Earth and are believed to possess atmospheres composed of hydrogen and helium.
Astrophysicist Jessica Libby-Roberts from Penn State noted the unusual nature of 'super-puff' planets, which have low mass and density, likening them to cotton candy. The formation mechanisms of these peculiar planets and the preservation of their atmospheres in the face of intense radiation from their young star remain unresolved mysteries.
The identification of the fourth low-mass planet occurred during an investigation of Kepler-51d by a research team from Penn State and Osaka University. The team was surprised when Kepler-51d transited in front of its host star, allowing for further analysis of its atmospheric composition through the absorption of starlight at specific wavelengths.