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The European “Cubes” space telescope has revealed that five of the distant outer planets of the solar system move steadily and symmetrically as if they are performing a dance, a phenomenon that has never been observed among stars whose diversity calls for a dance. revision of theories related to their formation, according to a recent study.
These planets, called exogenous because of their presence outside the solar system, orbit around their star “TOI-178” at the same level with a very precise temporal regularity, about 200 light years from Earth.
These planets follow the “series of resonances” that astronomer Laplace discovered at the end of the 18th century with three of Jupiter’s moons. And Laplace found that the time required for one cycle of Ganymede, which is the farthest, that the planet closest to Europe performs two rotations, while Io, which is closer to Jupiter, runs four.
The same mechanical movement applies to the TOI-178. The rotation of the first planet in the chain around the star takes about three days, while subsequent planets, each of which is further away from the previous one, need successively six days, then fifteen, fifteen and finally twenty, and the alignment of some of them are coordinated regularly.
An animated film expresses the phenomenon, in which music accompanies the movement of these planets. A sixth exoplanet, the closest to the star, spins at a very high speed, incompatible with the following planets.
“We only know of five other systems that work according to this mechanism,” in which a group of exoplanets coordinate in orbit around their star, said the lead author of the study, published this week in the journal Astronomy and Astrophysics, astronomer at the University. of the Geneva Observatory.
‘Linked system’
As for the astrophysicist from the University of Bern, Jannick Alliber, who participated in the preparation of the study, he stressed that the importance of the movement of these planets lies in the fact that they have probably remained unchanged since their formation, as if they were “a system frozen since the end of their formation phase, which lasts millions of years.” For more than two billion years have followed this stage until today.
At this point, things get complicated. Usually the density of the planets decreases as the distance from the star increases. In particular, however, the density of the third planet in the chain is much higher than that of the second. “There is a lot of diversity, which is surprising,” said Lilio.
He added: “On the one hand, we feel like something hasn’t moved for billions of years. Periods of planetary rotation are temporary within minutes, and they are regulated, and on the other we have these differences in density “. which contradict accepted theories regarding the formation of planetary systems.
It is assumed that the observation will continue with the European Space Agency’s “Cubes” telescope, which has been in Earth orbit since December 2019 with the aim of determining the initial specifications of planets outside the solar system, pending the use of its future successor, the “Hubble” Telescope, which will be launched this year, and is owned by James Web.
“Rosetta stone”
The participant in the scientific study in charge of the “Cubeus” team, Professor Kate Isek, told AFP that the TOI-178 system has an advantage in that this star is bright enough and that some of its planets are large enough to precisely study the atmosphere. of Earth and space. “.
The “Cubeus” team seeks to better understand the formation of planetary systems, and to detect, perhaps, exoplanets located at a greater distance than “TOE-178”.
“We want to know if there are planets more distant (…) than the sixth exoplanet”, said Professor Lilio. In the meantime, he and his colleagues seek to explore this system, which astronomers have described as a “rational stone” because it provides many answers to planetary formation, but at the same time raises the same number of questions.
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