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Building planetary systems: linking architectures with formation

Periodic Reporting for period 4 - BuildingPlanS (Building planetary systems: linking architectures with formation)

Berichtszeitraum: 2020-12-01 bis 2021-11-30

For hundreds of years our understanding of how planets form was limited to only the Solar System, but since the discovery of the first extra-solar planets (in the 1990s) our knowledge of planetary systems has increased at a startling rate; we now know of thousands of exoplanet systems. There have been many unexpected discoveries, but the biggest surprises was that most of the systems we observe look nothing like our own: we see “hot Jupiters” which orbit their stars in just a few days, planets which meander across entire solar systems on highly eccentric orbits, compact systems with five or six giant planets in tightly-packed short-period orbits, and even planets orbiting twin, binary suns. However, this huge advance in our knowledge has not yet led to a corresponding increase in our understanding, and many aspects of the planet formation process remain a mystery. The BuildingPlanS project aims to understand the origins of the enormous diversity we see in exoplanet architectures, by relating the properties of exoplanet systems to their formation in cold discs of dust and gas orbiting around young, newly-formed stars.
Our team has made several advances in our understanding of how young planets interact with their parent protoplanetary discs. We have developed new computer models of systems containing giant planets, which have sufficient mass to open gaps in their parent discs. Although these young planets are mostly invisible to our telescopes their effect on the discs can be observed, and we have shown how new data can be used to understand how young giant planetary systems form and evolve. We have also built sophisticated computer simulations of multi-planet systems, in order to understand how the gravitational interaction between planets can shape the formation and evolution of these systems. We have also studied of planets on inclined orbits, and planets and discs in binary systems, using large-scale computer simulations to model the dynamics, evolution, and observational appearance of these systems. We have shown that misalignments are common in forming planetary systems, and how both physical and chemical observational tracers can be used to understand the dynamics and evolution of misaligned discs. We have also shown that observations of the HD143006 system suggest it hosts both a binary star and a planet and, if confirmed, this will represent the first known example of a misaligned planet orbiting a binary star.
Planet formation spans a vast range in scales, but the intermediate stages of the process - everything from metre-size rocks up to Earth-size planets - are essentially invisible to our telescopes. As a result, theoretical models and computer simulations are the only way we can link the early stages of planet formation (in protoplanetary discs) with mature exoplanet systems. We have made important steps forward in understanding these early phases, and by linking new observations of discs to the physics of exoplanets, we have gained new and important understanding of the processes that shape planetary systems.
Numerical model and ALMA observation of the young star Elias 24, which hosts a forming planet.