Investigating to understand the reason for the disappearance of an exoplanet, astronomers have come to the conclusion that the latter never really existed. The Hubble telescope is said to have observed a collision of two objects and then the cloud of debris it generated.
In 1951, the film The clash of the worlds imagined that another planet was colliding with ours. Today, such a catastrophic scenario would have really taken place 25 light years from Earth. This hypothesis results from an investigation carried out since the sudden and unexplained disappearance of an exoplanet. In 2004, astronomers from the United States Aerospace Agency (NASA) and the European Space Agency (ESA) discover Fomalhaut-b, thanks to observations made with the space telescope Hubble. Ten years later, this exoplanet, orbiting one of the brightest stars in the Milky Way, disappears from radar. According to a recent study published by astronomers at the University of Arizona in Proceedings of the National Academy of Sciences, Formalhaut-b would never have existed!
“Clearly, Fomalhaut-b has never behaved like a real planet should”, points out one of the authors of this study, Andras Gaspar. As illustrated by a simulation performed by the images taken by Hubble (see below), the mass observed in orbit around Fomalhaut fades very quickly. According to the researchers, this mass is actually a huge cloud of rocks and stellar dust generated by the collision of two planetisimals. A planetisimal designates an unknown celestial body coming from a disc of planetary debris or, conversely, from a protoplanetary disc which when aggregated ends up forming a full-fledged planet. Following the collision of two planetisimals 200 kilometers in diameter, the cloud of debris formed gradually dispersed. The debris eventually became undetectable grains of dust of less than one micron. The diameter of this cloud would make today a size equivalent to the Earth-Sun distance. “These collisions are extremely rare, explains Andras Gaspare. To see one is therefore of major importance. ”
The Moon: the result of an inter-planetary collision?
For many scientists, such a collision could even have been at the origin of the formation of our natural satellite, the Moon. The “giant impact” hypothesis suggests that the planetoid Théia collided with the largest planet Earth about 100 million years after the formation of the solar system. The largest debris generated by this shattering encounter would then have gathered to give birth to the Moon and remain in orbit around the Earth. According to this theory, this collision would also have allowed our planet, then covered with magma, to cool.
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