Unique planetary system located at a distance of 200 lightsYears of Earth host five exoplanets with orbits linked together in a repeating pattern, despite their different sizes and densities. This discovery challenges astronomers Concepts of the types of planetary systems that can exist and how they form.
Five of the six exoplanets are in orbit around the star TOI-178 in an orbital resonance 18: 9: 6: 4: 3 with each other, according to the new Research Published today in Astronomy and Astrophysics. Therefore, for every 18 orbits created by the five closest exoplanets, the next planet along the chain will complete nine orbits during exactly the same period. The third will complete six orbits, and so on. The video below provides a demonstration of the process in progress.
The innermost portion of the six outer planets (marked by a blue orbital path) does not correspond to the other planets, although it may have been in the past. In the above animation, the rhythmic patterns are represented by red beats and a ringing sound (On the pentagonal scale), Which are triggered when each exoplanet completes either a full or half-orbit. As seen in the video, two or more exoplanets often trigger resonance as a result of being in an orbital resonance. The new study was led by Adrien Leleu, CHEOPS Fellow at the University of Geneva.
When Leleu, a dynamic (expert in celestial mechanics) and his colleagues first Noticing the TOI-178 system, they thought they saw two planets orbiting the host star in the same orbit, but this result was not conclusive. Scientists decided to make follow-up observations using tEuropean Space Agency CHEOPS satellite and ESPRESSO ground instrument at the European Southern Observatory Very large telescope, In addition to next one generation Crossing The survey And SPECULOOS ProjectsBoth are in Chile. Every tThese tools allowed the team to discover the six exoplanets and determine their orbits, which they did using the transit method (looking at Darkening of the host star when a planet passes in front) and by analogy The host star wobbled.
All six exoplanets are located in close proximity to the central star, and it takes about two days for the nearest planet to make a full orbit The farthest in orbit About 20 days. None of it is within the habitable zone, the Goldilocks region around a star where liquid water (and thus life) would be possible. Five of the six exoplanets are trapped in perfect resonance, like some planets They come in alignment every few orbits. The 18: 9: 6: 4: 3 series is among the longest series ever discovered.
Orbital resonance occurs when orbital bodies exert a periodic gravitational effect on one another. In our solar system, the moons of Jupiter Io, Europa, and Ganymede are in a 4: 2: 1 echo.
TOI-178 is interesting for a number of reasons, as orbital resonance is a sign of prolonged stability.
“From our understanding of planetary formations, a series of resonances often occur in the early stages of the formation of the planetary system, Lilio explained in an email that the star was still surrounded by a gas disk. “However, in the billions of years after formation, many things could happen and most systems would emerge from the echo. It could happen slowly because of [gravitational] Tidal effects for example, or violently, Due to instability and collision / ejection of the planet. “
He added that only five other star systems have resonant chains that include four or more planets, “that’s not much.” Astronomers consider these planetary systems to be rare and very recent.
“What defines TOI-178 is not only this orbital formation, but also the planetary formation,” said Leleu. This thus poses a challenge to our understanding of how planets form and evolve.
In fact, the size of the planets ranges between one and three tonsimes ground size But it has Its mass ranges from 1.5 to 30 times that of Earth. So, while their orbital formations are clean and tidy, their fixtures are not. For example, one planet is a super planet Earth, but its immediate neighbor is lowThe density of giant ice is comparable to Neptune. We don’t see that kind of thing here.
According to Leleu, the theory suggests that planets should be of lower density the further away from their star. But this is not the case here. “In TOI-178, this is only true for rocky inner planets, but then the third planet from the star is very low in density, then Planets 4 and 5 are denser, and then Planet 6 becomes thinner again again,” he said.
Astronomers will now have to figure out how the system was formed, including whether it was Some planets Formed farther out And slowly Aggravated inside.
Interestingly, the TOI-178 can host more distant ones Planets however They were not discovered. Looking to the future, the ESO’s upcoming Extremely Large Telescope, which should be operational later this decade, may be able to learn more about this strange star system.