Five of the six planets orbit the host star TOI-178 in a harmonious way, which is a rare fact, but all are “out of alignment” due to its density, which varies from planet to planet and is estimated according to its size and mass.
According to Adrian Lelu, the study’s coordinator at the University of Bern in Geneva and Switzerland, “the distinction between the rhythmic uniformity of orbital movements and the irregular densities clearly challenges the understanding of the formation and evolution of planetary systems.”
About 200 light-years from Earth, Portuguese researchers from the University of Lisbon, Porto and the University of Coimbatore and the Institute of Astronomy and Space Science (IA) participated in this work, which revealed the structure of the six planets orbiting the star TOI-178.
According to Sergio Sousa of the IA, who coordinates the observations and scientific conclusions of an instrument used to “hunt” these extraterrestrial planets, “it presents additional clues and constraints to the global theory that could explain the formation and evolution of this complex system.”
“From the point of view of formation theories, it is very difficult to explain what happened, so the same gas cloud that formed this star and its planets would cause a combination of unordered diversity and densities,” he told Lusa.
In the solar system, the planets are arranged in an orderly fashion, with Earth-like rocks being more dense, closer to the Sun, and gases such as Neptune farther away.
In contrast, Nathan Hara of the University of Geneva points out that in the TOI-178 system, “Neptune appears to be a planet as dense as Earth, next to a planet with a density of half Neptune,” which has been investigated and quoted in the OES report in Chile. The VLT telescope, among others, was used in observations in conjunction with the European Space Agency’s CHEOPS satellite.
Rather than an “orbital interest”, five stars on six planets “dance” around their star, indicating that the TOI-178 planetary system “has formed very smoothly since its inception,” read Jan Albert, an astronomer and co-author at the University of Bern.
“If this system had been significantly disturbed early in its life, for example by a massive impact, this weak orbital configuration would not have survived,” explains the OES report, an astronomical organization that is part of Portugal.
The planets in the TOI-178 system orbit their star “much closer and faster” than the Sun orbits the Earth. Inside, very close to the star and, according to Sergio Sousa, “this is not a clear synchronic view of the dynamics of the planetary system”, completes an orbit “in a few days”, advancing the OES.
Some planets have rocks, but are larger than Earth, while others are gases, although much smaller than the gas giants in the solar system.
The results of the study were published in the journal Astronomy and Astrophysics.