The new study shows that the TOI-178 system 200 light years from Earth contains at least six planets with rare orbits.
The discovery of planetary systems that are increasingly different from our own constantly challenges the understanding of astronomers. The recently discovered six-planet TOI-178 system in the Ngoc Phu constellation is a striking example.
Previously, when observing TOI-178 with NASA’s Transit Exoplanet Survey Satellite (TESS), scientists predicted that the star only had two planets in orbit. However, new, more precise observations from the European Space Agency (ESA) CHEOPS satellite – launched in late 2019 – revealed that the system contains at least six planets with rare trajectories.
In a report published in the journal Astronomy & Astrophysics on January 25, the team at the University of Geneva and Bern in Switzerland, led by Dr Adrien Leleu, said that with the exception of the near celestial planet. At most, the five planets outside of the TOI-178 system are “locked” in their repeating orbits. Scientists call this phenomenon orbital resonance, which means it repeats itself as the planets move around the star, with some planets every few orbits aligned together.
This resonance has already been observed in the orbits of the moon groups of Jupiter Io, Europa and Ganymede. In this one, for each of the orbits of Europe, Ganymede completes two orbits and Io completes four. This is a 4: 2: 1 model.
However, the resonance motion in the TOI-178 system is much more complicated as it involves five planets in an 18: 9: 6: 4: 3 pattern. Initially, scientists found only four planets in the chain. resonance, but based on the model they predicted that there must be another hidden planet in the system (the star’s fifth planet). Further observations from CHEOPS subsequently confirmed that this assumption was correct.
The TOI-178’s orbits are very well laid out, suggesting that the system has become quite “quiet” since its inception.
While the planets of TOI-178 revolve around the star in an orderly fashion, their density and size do not follow any particular pattern. One of its planets has the same dense surface density as Earth, next to a porous planet of similar size.
“This is the first time that we have observed such a configuration in a planetary system. Normally, the planets in the resonance chain have a decreasing density as they move away from the star, and it is this at what we expect, ”Adrien said. “New discovery challenges current theories on how planets were formed.”
Adrien’s team wants to continue using CHEOPS to further study the TOI-178 system, including the life skills of the planets and what happened to the planet in the innermost part of the system. to the resonance movement.
