Nature likes patterns, on a small and large scale. Take, for example, the Fibonacci sequence – the repeating pattern of numbers in which each subsequent number counts the sum of the previous two. The formula appears in the spiral shells of nautilus, but also in the arrangement of the planets in the solar system, the distances of which roughly correspond to the ratios of Fibonacci numbers.
But the rough synchronization of our planets is nothing compared to the exact alignment of five newly discovered exoplanets orbiting their parent star with such perfect harmony that it seems almost strange. According to a study published in the scientific journal Astronomy & Astrophysics, a solar system discovered by NASA’s Transiting Exoplanet Survey Satellite has at least six planets, five of which orbit the star – known as TOI-178 (or TESS). Object of Interest). 178) – in an exact ratio. This is known as a “chain of resonances”, or a series of occasions in which planets orbit a star while maintaining a partner with each other.
“A resonance between two planets is what happens when one completes a certain number of orbits, while the other does the same,” said dr. Nathan Hara, an astrophysicist at the University of Geneva and co-author of the article, wrote to Salon. . “They therefore periodically find themselves in the same setup and the strongest attraction between them is therefore always in the same direction.”
There are some details that make the new finding so striking. One is the fact that five planets are involved instead of two; as Hara explained, this makes it ‘one of the longest known chains’ of resonant planets. In the case of the exoplanets around TOI-178, they dance at a rhythm of 18: 9: 6: 4: 3. This means that each time the inner planet in the chain makes 18 orbits around TOI-178, the following one in a row makes nine orbits, and the one thereafter six orbits, and so on.
The finding is also significant because ‘in the known resonant chains, the farther the planet is from the star, the less it is, as in the solar system: Mercury, Venus and the earth, Mars, have a higher density than Jupiter, Saturn , Uranus and Neptune. ‘The stars orbiting the TOI-178 in synchronism, on the other hand, have unusual comparative densities.
“The inner planets are the densest, but then you have a planet with a very small Saturn-like density, then it goes up again and falls off,” Hara told Salon. “It does not break our understanding of planetary formation, but it is certainly enigmatic.”
He also told Salon that the discovery is useful to scientists because TOI-178 is an extraordinarily bright star – indeed the brightest star known to have resonant chains.
“Here, ‘transit’ means that the planet moves between the star and the observer, so that the starlight current measured by the observer decreases periodically,” Hara explained. “In this way, you also get an estimate of the radius of the planet. The fact that the star is brighter means that we can obtain information using other measurement techniques.”
Hara told Salon that, in addition to TESS, the discovery was made possible by recent advances in astronomical technology, including a European space agency telescope called CHEOPS, launched in 2019, and a modern spectrograph known as ESPRESSO that is employed since 2018.
“This one allows the velocity of the star to be measured in the direction of the line of sight and has unprecedented precision,” Hara explained. “We would not be able to do mass measurements of the planets of the system with the previous generation of spectrographs, or at the expense of extraordinarily long campaigns.”
On how the resonant chain exists on planets, Hara told Salon that he has a partial hypothesis.
“The formation of resonant chains is presumably the result of formations of planets separating wider from the star, which then migrate inward together and are trapped in resonance with each other,” Hara wrote. “As for the fact that the densities do not decrease monotonically as you move away from the star, we do not yet have a really convincing statement.”