An international team of scientists has observed for the first time how an exoplanet has been deformed by the force of its host star, an effect known as ‘rugby ball’ which, until now, astronomers had only theorized.
The results of this work, in which researchers from the Center for Astrobiology (CAB) have participated, were published on Tuesday in the revista Astronomy & Astrophysics.
Powerful tidal forces
The data, provided by the European Space Agency (ESA) CHEOPS mission, reveals that the exoplanet WASP-103b has been deformed by powerful tidal forces between the planet and its hotter and larger host star, WASP-103. than our sun.
“It takes less than a day for this exoplanet to circle its star and its shape is more like a rugby ball than a sphere“, Says Jorge Lillo-Box, researcher at the Center for Astrobiology and co-author of the study.
The phenomenon is not strange. On Earth, for example, the tides of the oceans are produced, a result of the influence of the Moon that ‘pulls’ slightly on our planet as it orbits us.
The Sun also has a small but significant effect on the tides, but it is too far from Earth to cause large deformations.
In this case, the star around which the exoplanet revolves, called WASP103, in the constellation Hercules, has a similar temperature and is about 1.7 times bigger than our Sun.
The exoplanet, WASP-103b, is a gas giant planet almost twice the size of Jupiter and 1.5 times its mass, and its extreme closeness to its host star could cause gigantic tides, something that until now has not been confirmed.
Data from ESA’s Cheops Space Telescope, Hubble and Spitzer
Using new data from ESA’s Cheops Space Telescope, combined with data from the NASA / ESA Hubble Space Telescope and NASA’s Spitzer Space Telescope, the astronomical community has been able to detect how tidal forces deform the exoplanet WASP-103b, giving it an oval shape.
These data have been complemented with high spatial resolution images from the AstraLux instrument at the Calar Alto Observatory (Almería), thanks to which the origin of the signal has been confirmed.
Cheops measures exoplanet transits, that is, the changes in light that occur when a planet passes in front of its star, but this time, its high precision has allowed it to detect the tiny signal that indicates that WASP-103b is undergoing a deformation caused by tidal forces.
How mass is distributed on the planet
The Cheops data have also made it possible to derive a parameter called the Love number, which measures how mass is distributed within a planet, which can give information about its internal structure and materials and determine in what proportion it can be rocky, gaseous or liquid.
“Understanding this internal structure is essential to understand the processes of formation and evolution of planetary systems,” says Jorge Lillo-Box.
The Love number of the exoplanet WASP-103b is similar to that of Jupiter, which suggests that the internal structure could be similar, despite the fact that WASP-103b has twice the radius.
This is because it is ‘inflated’, probably by the heat emanating from its host star and by other mechanisms that in the future can be studied with the James Webb Telescope, the largest space observatory in history that will help to find out much more. on the internal structure and nucleus of exoplanets and, therefore, on their formation.
The study also points out that the orbital period of WASP-103b could be increasing and that the planet is slowly moving away from the star, which would indicate that, along with tidal forces, there is another factor that influences the planet, but it will be more observations are needed to find out why this is happening.
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