Speeding up the six-exoplanet system with rhythmic movement challenges the principles of planetary formation


This artist’s conception depicts the view from the planet in the TOI-17 system that orbits far from the star. New research by Adrian Leleu and his colleagues, along with several telescopes, including ESO’s Very Large Telescope, has revealed that the system boasts six exoplanets and all but close to the star in a rare rhythm, which they call their own Go to classrooms. But while the orbital motion in this system is in harmony, the physical properties of the planet are more intractable, with significant changes in density from planet to planet. This contrast challenges astronomers’ understanding of how planets are formed and evolved. This artist’s belief is based on known physical parameters for planets and stars, and uses a vast database of objects in the universe. Credit: ESO / L. Calçada / spaceengine.org

Using a combination of telescopes, including the Very Large Telescope of the European Southern Observatory (ESO’s VLT), astronomers have revealed a system consisting of six exoplanets, five of which are locked in a rare rhythm of their central star. Researchers believe the system can provide important clues about how the planets and planets in the solar system evolve.

The first time the team saw TOI-178 about 200 light years away in the constellation of the sculptor, they felt that they had seen two planets revolving in the same orbit. However, a closer glance revealed something completely different. “Through further observation we realized that two of the planets were not orbiting at approximately the same distance, but many planets in a very particular configuration,” says Adrienne Leleu of the Universe Le Dave and the University of Bern, Switzerland. Were. “Which led to a new study of the system published today Astronomy and Astrophysics.

New research has revealed that the system boasts six exoplanets and that all but the closest to the star is locked in a rhythmic dance as they walk in their orbits. In other words, they are in resonance. This means that there are patterns that repeat themselves as the planets move around the stars, with some planets aligning every few orbits. A similar resonance is seen in the orbits of Jupiter’s three moons: Io, Europa and Ganymede. The io, closest to Jupiter’s three, completes four complete orbits around Jupiter that make Ganymede, farthest, and two complete orbits for every orbit Europa.

The five outer exoplanets of the TOI-17 system follow a more complex series of resonances, the longest discovered in the planetary system. While the three Jupiter moons are in the 4: 2: 1 resonance, the five outer planets in the TOI-178 system follow the 18: 9: 6: 4: 3 series: while the star (first) resonant series from the second planet) 18 orbits. Completes, the third planet from the star (the second in the series) completes 9 orbits, and so on. In fact, scientists initially found only five planets in the system, but following this resonant rhythm, they calculated that an additional planet in its orbit would be when they had a window to observe the system.

More than just an orbital curiosity, this dance of resonant planets provides clues about the system’s past. “Classes in this system are very well ordered, which tells us that this system has evolved quite slowly since its birth,” explains co-author Yann Elibert of the University of Bern. If the system was disturbed enough earlier in its life, for example by a huge impact, this delicate configuration of classes would not survive.

Speeding up the six-exoplanet system with rhythmic movement challenges the principles of planetary formation

This graphic shows the representation of the TOI-178 planetary system, revealed by ESA’s exoplanet watcher CHEOPS. The system consists of six exoplanets, five of which are locked in a rare rhythmic dance as they orbit their central star. The two inner planets have terrestrial densities (eg Earth) and the outer four planets are gaseous (with densities such as Neptune and Jupiter). The five outer planets follow a rhythmic dance as they walk in their orbits. This phenomenon is called orbital resonance, and means that there are patterns that repeat themselves as the planets go around the star, with some planets aligning every few orbits. While the planets in the TOI-178 system orbit their stars in a very ordered way, their densities do not follow any particular pattern. One of the exoplanets, a dense, terrestrial planet like Earth, is right next to a similar-sized but very fluffy planet – like a mini-Jupiter, and a Neptune next to it. Astronomers did not expect to find this lay-out in a planetary system, and this discovery challenges current theories of planet formation. In this graphic, the relative size of the planets is to be measured, but not the distance and the size of the stars. Sincerely: ESA

Disorders in rhythmic system

But even though the arrangement of the orbits is tidy and well-organized, the density of planets is “more disorganized,” says Nathan Hara of the Université de de Jave, Switzerland, who was also involved in the study. “It appears that right next to a very fluffy planet with a density of Neptune is a planet in the form of Earth, followed by a planet with a density of Neptune. This is not what we are used to. ” In our solar system, for example, planets are neatly arranged, excluding rocky, dense planets close to the central star and fluffy, low-density gas planets.

“This contrast between the rhythmic coherence of the orbital motion and the disordered density certainly challenges our understanding of the evolution and evolution of planetary systems,” says Leleu.

Technology combination

To investigate the system’s unusual architecture, the team used data from the European Space Agency’s CHEOPS satellite, which is based on ESO’s VLT and NGTS and SpecULOOS, which sits at ESO’s Paranal Observatory in Chile. Since exoplanets are extremely difficult to spot directly with telescopes, astronomers must rely on other techniques to detect them. The main methods used are imaging transits – observing the light emitted by the central star, which is dimmed as an exoplanet when viewed from Earth – and radial velocity – for small signals of starlight starlight Observe the spectrum that occurs in exoplanets in their orbits. The team used both methods to follow the system: CHEOPS, NGTS and SPECULOOS for radial velocity.

By combining the two techniques, astronomers were able to gather important information about the system and its planets, which orbit their central star much closer than the Earth and orbit the Sun. The fastest (innermost planet) completes an orbit in just one or two days, while the slowest takes about ten times longer. The size of the six planets is about one to three times the size of the Earth, while their mass is 1.5 to 30 times the mass of the Earth. Some planets are rocky, but larger than Earth – these planets are known as super-Earths. Others are gas planets like the outer planets in our solar system, but they are very small – they are nicknamed Mini-Neptune.

Although none of the six exoplanets were found in the habitable zone of the star, researchers suggest that by continuing the resonance chain, they may find additional planets that may be present in or very close to the region. ESO’s Extremely Large Telescope (ELT), which is set to begin operating this decade, will be able to image rocky exoplanets directly in the habitable zone of a star and even characterize its atmosphere, here Will also present an opportunity to learn systems like TOI-178. greater detail.


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more information:
A. Leleau et al. TOI-178 consists of six transit planets and a series of Laplace echoes, Astronomy and Astrophysics (2021). DOI: 10.1051 / 0004-6361 / 202039767

Quotes: How to form a six-exoplanet system with rhythmic movement, challenging the principles of planetary form (2021, 25 January) on 26 January 2021 https://phys.org/news/2021-01-puzzling-six-exoplanet- Retrieved from rhythmic-movement. theory. html

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