ESO: Puzzling Six-Exoplanet System with Rhythmic Movement

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ESO: Puzzling Six-Exoplanet System with Rhythmic Movement

Post by bystander » Tue Jan 26, 2021 1:02 am

Puzzling Six-Exoplanet System with Rhythmic Movement
Challenges Theories of How Planets Form

Click to play embedded YouTube video.
TOI-178 orbits and resonances (sound on!) ~ Credit: ESO/L. Calçada
This animation shows a representation of the orbits and movements of the planets in the
TOI-178 system. ... In this artist’s animation, the rhythmic movement of the planets
around the central star is represented through a musical harmony, created by attributing
a note (in the pentatonic scale) to each of the planets in the resonance chain. This note
plays when a planet completes either one full orbit or one half orbit; when planets align
at these points in their orbits, they ring in resonance.

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 around their central star. The researchers believe the system could provide important clues about how planets, including those in the Solar System, form and evolve.

The first time the team observed TOI-178, a star some 200 light-years away in the constellation of Sculptor, they thought they had spotted two planets going around it in the same orbit. However, a closer look revealed something entirely different. ...

The new research has revealed that the system boasts six exoplanets and that all but the one closest to the star are locked in a rhythmic dance as they move in their orbits. In other words, they are in resonance. ... The five outer exoplanets of the TOI-178 system follow a much more complex chain of resonance, one of the longest yet discovered in a system of planets. ... the five outer planets in the TOI-178 system follow a 18:9:6:4:3 chain ...

But even if the arrangement of the orbits is neat and well-ordered, the densities of the planets “are much more disorderly,” says Nathan Hara ... “It appears there is a planet as dense as the Earth right next to a very fluffy planet with half the density of Neptune, followed by a planet with the density of Neptune. It is not what we are used to.” ...

“This contrast between the rhythmic harmony of the orbital motion and the disorderly densities certainly challenges our understanding of the formation and evolution of planetary systems,”
says Adrien Leleu. ...

To investigate the system’s unusual architecture, the team used data from the European Space Agency’s CHEOPS satellite, alongside the ground-based ESPRESSO instrument on ESO’s VLT and the NGTS and SPECULOOS, both sited at ESO’s Paranal Observatory in Chile. Since exoplanets are extremely tricky to spot directly with telescopes, astronomers must instead rely on other techniques to detect them. The main methods used are imaging transits — observing the light emitted by the central star, which dims as an exoplanet passes in front of it when observed from the Earth — and radial velocities — observing the star’s light spectrum for small signs of wobbles which happen as the exoplanets move in their orbits. The team used both methods to observe the system: CHEOPS, NGTS and SPECULOOS for transits and ESPRESSO for radial velocities.

Exoplanet Watcher CHEOPS Reveals Unique Planetary System
ESA | Space Science | Science & Technology | CHEOPS | 2021 Jan 25

CHEOPS Finds Unique Planetary System
University of Bern | 2021 Jan 25

Six Transiting Planets and a Chain of Laplace Resonances in TOI-178 ~ A. Leleu et al Co-orbital Exoplanets from Close-Period Candidates: the TOI-178 case ~ A. Leleu et al
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