An international team of astronomers (including scientists from the Instituto de Astrofísica de Canarias), has discovered 200 light years from us in the constellation Sculptor, a somewhat unique system of six planets, since five of them dance at a strange rhythm around from its central star, TOI-178. Its rhythm reveals a star system that has not been disturbed by cosmic events since its birth.
Although we have seen this phenomenon known as resonance before in other planetary systems, it is the first time that the planets of the same are completely different from each other.
The researchers used the European Space Agency’s CHEOPS space telescope to detect the unusual formation . The astronomers found that five of the six planets are locked in a harmonic rhythm, where their orbits line up in a consistent pattern with each other.
This 7.1 billion-year-old planetary system could provide important clues about how planets form and evolve, experts say in their study published in the journal Astronomy & Astrophysics.
The five outer planets are in a resonance chain of 18: 9: 6: 4: 3. A resonance of 2: 1 would show that for each orbit of the outer planet, the inner one makes two. In the case of TOI-178, this means the following bewildering rhythmic dance: for every three orbits of the outermost planet, the next makes four, the next makes six, the next makes nine, and the last (the second from the star) makes 18.
The density of the planets in the system is also unusual: In the solar system, the dense rocky planets are closest to the Sun, followed by lighter gas giants. In the case of the TOI-178 system, a dense Earth-like planet is right next to a very spongy planet with half the density of Neptune, followed by a Neptune-like one . This peculiar design together with its orbital resonance “challenges what we know about how planetary systems form,” according to the authors.
“The orbits of this system are very well ordered, which tells us that this system has evolved quite smoothly since its birth,” explains Yann Alibert from the University of Bern and co-author of the work.
In fact, the resonance of the system shows that it has remained relatively unchanged since its formation. Had it been disturbed earlier, either by a giant impact or the gravitational influence of another system, the fragile configuration of its orbits would have been erased. But it has not been that way.
“This is the first time we have observed something like this. In the few systems we know of with such harmony, the density of the planets constantly decreases as we move away from the star,” said ESA co-author and project scientist Kate. Isaak.
As we have discussed, these distant planets are not the only objects in space that we know to follow resonance orbits . Three of Jupiter’s moons, Io, Europa, and Ganymede, do something similar. For each orbit of Europa, Ganymede completes two orbits and Io completes four. Astronomers would say that this is a 4: 2: 1 pattern.
Referencia: A. Leleu, Y. Alibert, N. C. Hara, M. J. Hooton, T. G. Wilson, P. Robutel, J.-B. Delisle, J. Laskar, S. Hoyer, C. Lovis, E. M. Bryant, E. Ducrot, J. Cabrera, J. Acton, V. Adibekyan, R. Allart, C. Allende Prieto, R. Alonso, D. Alves, D. R. Anderson, al. Six transiting planets and a chain of Laplace resonances in TOI-178. Astronomy & Astrophysics, 2021; DOI: 10.1051/0004-6361/202039767
