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Evolution of the Early Solar Nebula: Isotopic Fractionation and Dynamical Processes

Applicant Dr. Dmitry Semenov
Subject Area Astrophysics and Astronomy
Term from 2010 to 2016
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 144426989
 
Final Report Year 2022

Final Report Abstract

This project aimed to improve our understanding of how our solar system - and others like it - formed and evolved. The team focused on the very early evolutionary stage, when planet formation had just begun in a rotating disk of gas, dust, and ices (the solar nebula), eventually giving rise to planets, asteroids, and comets. To do this, the team developed advanced computer models and tools to simulate the physical conditions and the chemistry occurring in these planet-forming disks. A first significant achievement was extending the "ALCHEMIC" gas-grain chemical kinetics code to operate in dynamically active planet-forming disks. This is a powerful model to simulate chemical processes in the gas and ice phases in the solar nebula. The effects of cosmic rays, ultraviolet light, and X-rays on nebular chemistry, all of which influence how molecules form or break apart, were considered. This code is made publicly available. In addition, the team has helped develop a comprehensive physical-chemical model called "ANDES", where the "ALCHEMIC" code was used as a chemical "engine". "ANDES" models time-variable physical conditions and chemical evolution in the early solar nebula and other planet-forming disks. This model also includes dynamics, growth, and settling of dust particles and the effects of luminosity outbursts due to irregular accretion. An important aspect of the research was studying how turbulent mixing within the solar nebula changes ist chemical composition. Turbulence can stir up the material, moving ices and gases from cold, shielded regions into warmer areas where they can react differently. This mixing helps explain the presence of complex organic molecules and even affects water distribution. The chemodynamical model successfully reproduced key observations - such as the ratios of deuterium (a heavy form of hydrogen) found in water - in the Earth’s oceans, carbonaceous asteroids, and comets. The project also made significant steps in linking theoretical models with real astronomical observations. Collaborations with observers using powerful telescopes like ALMA allowed the project team to test their predictions against measurements of molecular emissions from nearby disks. These comparisons have provided new insights into the structure, temperature, and chemistry of disks around young stars, helping to validate the models. In summary, the outcomes of the project have advanced our knowledge of the early solar system by: 1) Developing new simulation tools that realistically combine physics and chemistry. 2) Demonstrating how dynamic processes such as turbulence can shape the chemical environment of planet-forming disks. 3) Providing a better understanding of water’s origins and ist delivery to Earth. 4) Developing new modeling tools that can aid in the interpretation of telescope observations.

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