Vue d'artiste de la planète WASP-103b et de son étoile parent ? © ESA

An atypical rugby ball exoplanet: no one has heard of it!

As part of the European Space Agency’s Khufu mission, an exoplanet twice the size of Jupiter was discovered orbiting close to its star. The result, the effect of the tides so that the planet is, completely distorted, shaped like a rugby ball!

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[EN VIDÉO] outer planets
What are exoplanets, where are they and why are they interesting? The answer is in the video!

The satellite was launched at the end of 2019 Khufu (characterizes the outer satellite of the planets) The main mission of the European Space Agency is to study stars close to our planet Soleil, known for harboring the exoplanets in star systems. With its high measurement accuracy, the mission aims, among other things, to accurately characterize the sizes and density of the discovered exoplanets.

Among these study subjects is WASP-103, a star located in constellation From Hercules around orbiting WASP-103b, A extrasolar planet Twice the size of Jupiter and 1.5 times larger. When it was discovered in 2014, it was Astronomy scientists Surprised by its proximity to its star (WASP-103b completed a revolution in just one day), they suspected that the planet had been subjected to intense tidal effects, without being able to measure them.

The transit method for observing the exoplanets … but also for deducing their shape!

Khufu satellite is used transit method To observe and characterize the outer planets. by measuring brightness For a star, we can detect a periodic decrease in its luminosity associated with the passage of a celestial body in front of the star: this is called a transit. By comparing 12 transits of the planet, astronomers have discovered subtle differences between different Transitassociated with the deformation of the planet. This is the first time that a deformation of an exoplanet has been detected in this way.

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huge tidal effects

Tides are a well-known phenomenon on Earth: the masses of water on the surface of our planet are subject to the gravitational attraction that it exerts the moon. But for WASP-103b, the magnitude of the phenomenon is much larger: due to its close proximity to its star, tidal effects are very pronounced, distorting the entire planet. Thus, the planet no longer had a spherical shape, but the shape of a rugby ball!

Certainly, astronomers inwho – which Estimated the number of love, a parameter of distinction arrogance A planetary body and its susceptibility to deformation under the influence tidal forces. This parameter also allows to estimate the composition of the planet: at a value very close to that of Jupiter, it is very likely that WASP-103b presents a very close internal composition and structure, with fluid behaviour.

The researchers were surprised by the unusually large size of the planet: in principle, a planet 1.5 times the size of Jupiter should have a relatively similar size. Here, astronomers suspect the planet is inflated due to the heat extremes that prevail near its star, but this has not yet been confirmed.

The planet’s orbit raises new questions

Given its proximity to its star, astronomers expected that tidal interactions, combined with its proximity to the star, would cause WASP-103b’s orbit to shrink over a period of time and the planet gradually fall toward its star. However, measurements indicate the opposite, the orbital From the planet is slowly increasing: the planet is in fact slowly moving away from its star. Astronomers are currently searching for potential phenomena that dominate the effects of tides, which could cause such a drift.

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