Astronomers discover a planet shaped like a rugby ball

ESA’s Cheops exoplanet mission has revealed that an exoplanet orbiting its host star has a warped shape more like a rugby ball than a sphere.

This is the first time that the deformation of an exoplanet has been detected, offering new insights into the internal structure of these star-hugging planets. THAT it’s a statement.

The planet, known as WASP-103b, is located in the constellation Hercules. It has been deformed by the strong tidal forces between the planet and its host star. WASP-103, which is about 200 degrees hotter and 1.7 times bigger than the Sun.

Using new data from the space telescope Cheops from THAT, combined with data that had already been obtained by the NASA / ESA Hubble Space Telescope and the Spitzer Space Telescope of the NASAastronomers have now been able to detect how tidal forces warp exoplanet WASP-103b, transforming its appearance from the usual sphere to a rugby ball.

Cheops measures exoplanet transits: the decrease in light that occurs when a planet passes in front of its star from our point of view. Usually studying the shape of the light curve will reveal details about the planet, such as its size. The high precision of Cheops Along with its aiming flexibility, which allows the satellite to return to a target and observe multiple transits, it has allowed astronomers to detect the tiny signal from the tidal warp of WASP-103b. This distinctive signature can be used to reveal even more about the planet.

“It is incredible that Cheops was able to reveal this small deformation”says in a statement Jacques Laskar from the Paris Observatory, Université Paris Sciences et Lettres, and co-author of the research. “This is the first time that such an analysis has been performed, and we can hope that observation over a longer time interval will strengthen this observation and lead to a better understanding of the internal structure of the planet. “

The team was able to use the transit light curve of WASP-103b to derive a parameter, the Love number, which measures how mass is distributed within a planet. Understanding how mass is distributed can reveal details about the internal structure of the planet.

“The resistance of a material to deformation depends on its composition ”, explains Susana Barros, from the Instituto de Astrofísica e Ciências do Espaço and the University of Porto, Portugal, and lead author of the research. “For example, here on Earth we have tides due to the Moon and the Sun, but we can only see the tides in the oceans. The rocky part doesn’t move that much. By measuring how much the planet deforms, we can tell how much it is rocky, gaseous or water. “

The Love number for WASP-103b is similar to Jupiter, tentatively suggesting that the internal structure is similar, despite the fact that WASP-103b has twice the radius.

“In principle, we would expect a planet with 1.5 times the mass of Jupiter to be roughly the same size, so WASP-103b must be very inflated due to the heating of its star and perhaps other mechanisms.s ”, dice Barros.

“If we can confirm the details of its internal structure with future observations, perhaps we can better understand what it is that makes it so inflated. Knowing the size of the nucleus of this exoplanet will also be important to better understand how it formed.

Since the uncertainty in the Love number is still quite high, future observations with Cheops and the Space Telescope will be needed. James Webb (Webb) to figure out the details. Webb’s extremely high precision will improve measurements of the tidal deformation of exoplanets, allowing a better comparison between so-called “hot Jupiters” and the giant planets of the Solar System.

Another mystery also surrounds WASP-103b. Tidal interactions between a star and a very close Jupiter-sized planet would generally cause the planet’s orbital period to shorten, gradually bringing it closer to the star before it is finally engulfed by the parent star. However, measurements from WASP-103b seem to indicate that the orbital period could be increasing and that the planet is slowly moving away from the star. This would indicate that something other than tidal forces is the dominant factor affecting this planet.

Barros and his colleagues looked at other potential scenarios, such as a host’s companion star affecting the dynamics of the system or the planet’s orbit being slightly elliptical. They couldn’t confirm these scenarios, but they couldn’t rule them out either. It is also possible that the orbital period is actually decreasing, rather than increasing.