ESA's exoplanet hunter detects deformed planet for the first time

The European Space Agency's exoplanet watcher - Cheops - has detected the deformation of an extrasolar planet for the first time. Named WASP-103b, the planet is located in the constellation Hercules and is almost twice the size of Jupiter with 1.5 times its mass.

Astronomers say that the exoplanet has been deformed by the strong tidal forces between it and its host star WASP-103, making it look more like that of a rugby ball than a sphere. They used new data from ESA's Cheops space telescope and combined it with the NASA/ESA Hubble Space Telescope and NASA's Spitzer Space Telescope to detect tidal deformation of WASP-103b.

"This is the first time such analysis has been made, and we can hope that observing over a longer time interval will strengthen this observation and lead to better knowledge of the planet's internal structure," said Jacques Laskar of Paris Observatory, Université Paris Sciences et Lettres, and co-author of the research.

The researchers also revealed another mystery surrounding this rugby ball-shaped planet. Tidal interactions between a star and a very close-in Jupiter-sized planet would usually cause the planet's orbital period to shorten, bringing it gradually closer to the star before it is eventually engulfed by the parent star. However, in the case of WASP-103b, measurements seem to suggest that the orbital period might be increasing and the planet is drifting slowly away from the star.

Astronomers believe that something other than tidal forces is the dominant factor affecting this planet. Additional observations of the transits of WASP-103b with Cheops and other telescopes will help shed light on this mysterious motion.

Launched in 2019, Cheops or the Characterising Exoplanet Satellite is ESA's first mission dedicated to the study of exoplanets. It will observe bright stars that are already known to host planets, measuring minuscule brightness changes due to the planet's transit across the star's disc.