TOI-421 planetary system reveals inclined orbital architecture

An international team led by the University of Geneva (UNIGE), including scientists from the National Center of Compentnce in Research Planets, the University of Warwick and Canary Islands Institute of Astrophysics, launched an ambitious program to map the exoplanets around the Neptunian desert. The objective: to better understand the training and evolution of planetary systems.

This collaboration, known as Atreids, gave its first results with the observation of the planetary system to 421. The analysis of this system reveals a surprisingly inclined orbital architecture, offering new perspectives on the chaotic history of these distant worlds.

This inaugural study is published in the journal Astronomy and astrophysics.

What are the physical mechanisms that govern the training and evolution of planetary systems? To answer this large question, scientists led by the Unige’s astronomy department have decided to focus on a specific class of exoplanets: exo-neptunes, planets outside of our solar system which are about 20 times more massive than earth.

Over the past decade, scientists have made major discoveries on the distribution of exoplanets. Ex-neptunes are absent in regions very close to the stars. However, recent studies in which UNIGE participated show that in slightly more distant areas of the stars – a region more temperate in the distribution of exoplanets known as “savannah” – this type of planet is more widespread. Finally, between this savannah and the desert is a region called the “Neptunian ridge”, where exo-neptunes are even more numerous than in the other two regions.

“The complexity of the Exo -Neptunian landscape offers a unique window on the processes involved in the training and the evolution of planetary systems. This is what inspired the ambitious scientific cooperation of the atreids, which is based in particular on a large -scale observation program that we are leading on the largest European telescopes – the expressions of the ESO – Expressing the” Specter of the world ” Department of astronomy of the Faculty of Sciences of Unige, principal researcher of the Atreids program and principal author of the first study of the consortium.

Conquer the “desert”

The ATREIDS program focuses on exo-naps to identify the processes responsible for the Neptunian ridge, savannah and desert, and to derive more general information on the training and evolution of planets. Scientists plan to use espresso to observe a large number of neptons and analyze and model data from all planets in a coherent and coherent framework. This systematic approach should allow a real comparison between different planetary systems and a better understanding of the mechanisms that shape this complex Néptunian landscape.

Designed as an open international community initiative, Atreids collaboration invites all astronomers interested in joining this scientific effort, following the example of the University of Warwick.

“We use NGTS telescopes, an exoplanet observation program based on the transit method, to observe the transits of these Neptunes and thus optimize our use of the espresso / VLT.

To 421: an orbital architecture “Mal aligned”

The first system observed and analyzed within the framework of the atreids is called TOI-421. He has two planets: a hot neptune, to 421 C, located in the savannah, and a smaller planet closer to the star, to-421 b. Astronomers were able to trace the chaotic history of this system.

One of the hypotheses of the Atreid program stipulates that the Néptuen landscape was sculpted by the way in which these planets have migrated from their place of birth to their current orbits. Some planets would migrate slowly and early through the gas disc in which they have formed, a process that should produce aligned orbits. Others would be violently propelled into their orbits much later, thanks to a chaotic process called “high content migration”, which results in very poorly aligned orbits.

One of the key variables of this hypothesis is therefore the alignment between the equatorial plane of the star and the orbital plane of each planet. By measuring this alignment for you-421, scientists have been able to show that the two planets of the system are very badly aligned, which is very different from our solar system where the planets are aligned and therefore turn almost in the equatorial plane of our sun. This indicates a turbulent story in the evolution of the TO-421 system after its training.

The analysis of Tou-421 is just a taste of what is to come. It provides valuable information to scientists, but also and above all, helps refine the analysis and modeling tools developed in Atreid collaboration. However, a large number of planetary systems with exo-neptunes will have to be observed and analyzed with the same rigor before being able to describe the evolution and formation of planetary systems.

“An in -depth understanding of the mechanisms that shape the Neptunian desert, the savannah and the crest will provide a better understanding of the planetary training as a whole … But it is a safe bet that the universe has other surprises in reserve, which will force us to develop new theories”, concludes the stuffing.