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UC researcher helps to discover rugby ball-shaped exoplanet

11 january
Artist impression of planet wasp103b and its host star.
Artist impression of planet wasp103b and its host star.
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An international research team which includes Alexandre Correia, of the Centre for Physics of the University of Coimbra (UC) has detected the deformation of an exoplanet for the first time. WASP-103b orbits a star that is 1.7 times wider and around 200ºC hotter than the sun. This exoplanet presents the unusual feature of having the shape of a rugby ball.

The study results from observations carried out by the European Space Agency (ESA) special mission Cheops, and has just been published in the journal Astronomy & Astrophysics.

This is the first time that the deformation of an exoplanet was detected, providing new data about the internal structure of these planets surrounded by stars. The discovery is based on a hypothesis raised six years ago by Alexandre Correia and Jacques Laskar, director of the Institute of Celestial Mechanics and Ephemeris Calculation of the Paris Observatory. From the results of Alexandre Correia's theoretical study, it was suggested that CHEOPS might be able to detect the deformation of a planet.

“We knew that this would be extremely challenging, and after researching all eligible candidates, we selected WASP-103b as the best target for the mission. Although we had already predicted it, it was a surprise to see that Cheops was indeed able to spot that small deformation. This is the first time such an analysis has been done and we hope that observation over a longer time interval will strengthen this finding and lead to a better understanding of the internal structure of the planet.", state Jackes Laskar and Alexandre Correia, co-authors of the study.

By combining observations of transits of the exoplanet carried out by Cheops with data already known from the Hubble Space Telescope (NASA/ESA) and the Spitzer Space Telescope (NASA), the team was able to confirm that the planet is indeed wider at the equator than at the poles, and that its shape resembles a rugby ball. The extreme precision of the CHEOPS observations may be used to reveal even more information about the internal structure of this deformed planet.

CHEOPS Consortium is led by Switzerland and counts on the participation of eleven european countries. The scientific article is called ‘Cheops reveals the tidal deformation of WASP-103b’ by S.C.C. Barros et al. (2021) is available at

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