The animation above represents the orbits and movements of planets in the TOI-178 star system. All but one of these six exoplanets is closed in rare resonance classes. This star is about 200 light years away. As the planets orbit stars, they form patterns that repeat themselves rhythmically, with some planets aligning every few orbits. The European Space Agency – which announced the new discovery today (January 25, 2021) – said that the planets were found in data collected by its telescope planetary, a telescope in space. His release said that the discovery:
… challenges current theories of planet formation.
The results were published today (January 25, 2021) in the magazine Astronomy and Astrophysics.
In the artist’s animation above – that is through the European Southern Observatory – the rhythmic motion of the planets around their central star is characterized by a musical harmony:
… Attributing one note (in Pentatonic scale) to each planet. This note follows when a planet completes one full orbit or one half orbit; When the planets align at these points in their orbits, they ring in resonance.
So in the TOI-178 system, five regions of the world make a kind of music. Meanwhile, the ESA said, the planets have very different creations from each other.
These distant planets are not the only objects in space that are known to follow resonant orbits. Jupiter’s three moons – Io, Europa and Ganymede – do something similar. For each class of Europa, Ganymede completes two classes, and Io completes four. Astronomers say that this is a 4: 2: 1 pattern. ESA explained:
In the TOI-178 system, the resonant motion is much more complex because it consists of five planets following an 18: 9: 6: 4: 3 pattern. While the second planet from the star (the first in the pattern) completes 18 orbits, the third planet from the star (the second in the pattern) completes nine orbits, and so on.
Astrophysicist Adrian Leleu of the University of Bern, University of Geneva and the National Center of Competition at Research Planets led the research. His team found connections between five of the five planets orbiting the star TOI-178. Leleau said:
This result shocked us, as previous observations with NASA’s Transiting Exoplanet Survey Satellite (TESS) pointed to a three-planet system simultaneously orbiting two planets. We therefore observed the system with additional equipment, such as the ground-based ESPRESSO spectrograph at Paranal Observatory of the European Southern Observatory (ESO) in Chile, but the results were inconclusive.
When Leleau and his colleagues first proposed examining the system more closely, they were not sure what they would find. Leleau said:
After analyzing the data for 11 days observing the system with CHEOPS, it seemed that there were more planets than we initially thought.
The team had identified at least five planets. They decided to invest another day of precious observation time on the system to confirm. They found that five planets actually existed with a revolving period of 2, 3, 4, 10 and 20 days respectively.
While a system with five planets would have been a fairly remarkable discovery in itself, Leleau and his colleagues saw that there could be more to the story: the system seems to be harmonious. Leleau explained:
Our theory implied that there may be an additional planet in this harmony; However, its circumambulation period should be around 15 days.
To test whether their theory was indeed correct, the team set up another observation with the CHEOPS at the right time, which would pass through this missing planet, if it existed. But then, an accident threatened to cancel his plans. Co-author Yan Alibert at the University of Bern commented:
Just before the time of observation, a piece of space debris threatened to hit the CHEOPS satellite.
Therefore, the Control Center of the European Space Agency (ESA) launched an initiative
The satellite’s maneuver and all comments were interrupted. Another co-author, Nathan Hara of the University of Geneva, said:
But to our great relief, this maneuver was performed very efficiently and the satellite may resume observations to pass through the mysterious planet for some time. A few days later, the data clearly indicated the presence of additional planets and thus confirmed that there were indeed six planets in the TOI-137 system.
With this came another surprise: their density seems to be a wild mixture, compared to the harmonic, orbiting planets around its star. ESA project scientist Kate Issac said:
This is the first time we have seen something like this. In some systems we know with such cohesion, as we move away from the stars, the density of the planets steadily decreases. In the TOI-178 system, a dense, terrestrial planet resembling the Earth appears to be right next to a very fluffy planet, which has half the density of Neptune, followed by one similar to Neptune.
Adrian Leleau concluded:
The system is therefore one that challenges our understanding of the formation and evolution of planetary systems.
Bottom line: The star system TOI-178 is now known to have 6 exoplanets, all but closed in rare resonance orbitals. As planets orbit stars, they form patterns that repeat rhythmically, with some planets aligning every few orbits. The European Space Agency announced the discovery on 25 January 2021. It was said that the planets were found in the data collected orbiting it by its orbiting planet-predator telescope.
Source: Six transit planets in TOI-178 and a series of Laplace echoes
Through the University of Bern