Studying Planetary Systems in the Making
Aiming to understand how planetary system form, Joanna Drążkowska heads a Lise Meitner Group at the MPS.
How do planets form from the disks of gas and dust that orbit around young stars? At the Max Planck Institute for Solar System Research (MPS) in Germany, Joanna Drążkowska is investigating this question within the framework of a Lise Meitner Group of the Max Planck Society (MPG). The researcher's goal is to describe the entire development, spanning billions of years, from the smallest dust grains to the largest planets, in a unified model and to simulate it on the computer. Only in this way can the diversity of planets – in our solar system and beyond – be understood. The models are tested against observational data from the depths of space and analyses of meteorites, such as those carried out at the MPS. Already, it is apparent that planet formation is much more complex and less straightforward than previously assumed. The MPG's Lise Meitner Excellence Program supports exceptionally qualified female scientists and offers them the prospect of continuing their research within the MPG on a permanent basis.

To say that our Solar System is just one planetary system among many is a huge understatement. According to current estimates, the vast majority of the approximately one hundred billion stars in our Milky Way are surrounded by planets. However, the individual planetary systems can turn out very differently: Some stars are orbited by only a single planet, while others are home to several, and some – like the Sun – have as many as eight or more worlds in their gravitational grasp. In addition, size, distance, and composition of the planetary “inhabitants” vary greatly from planetary system to planetary system. This incredible diversity challenges traditional ideas about planet formation, originally meant to reflect the Solar System only. Modern theories have to do better. “We are trying to understand how the same processes that shaped our own Solar System can also lead to completely different architectures of planetary systems,” says Drążkowska, describing her research.
A string of gas giants
Previous models described planet formation as a rather straightforward process: The dust grains originally orbiting within a disc of gas and dust around a young star after first combine to form tiny clumps; these merge into ever larger clumps, pebbles and chunks ... until the rocky planets and the cores of the gas giants are formed. According to this idea, planetary evolution follows a clear “timeline” and planets can form anywhere within the disk of gas and dust.
But this theory is no longer tenable. “Our results show that all phases of planet formation are interdependent and can well proceed in parallel,” explains Drążkowska. The researcher was able to show that a nascent gas planet can have a retroactive effect on the remaining gas and dust disk in its vicinity and accumulate dust nearby. In this way, the planet amasses the building blocks for the next gas giant. This process can occur multiple times and thus create an entire sequence of gas planets within a planetary system much more efficiently and quickly than previously assumed. In our Solar System, the planets Jupiter, Saturn, Uranus and Neptune could have formed in this way. Therefore, for the first time Drążkowska and her team intend to describe and simulate all phases of planet formation – from the smallest dust particle to the largest planet – within one model.

In the case of our Solar System, the insights gained in this way can be compared with the results of meteorite analyses. Meteorites are chunks of rock that have made their way from the depths of the Solar System to Earth. They have changed little since their formation and thus bear witness to the evolution of our Solar System. In laboratory experiments, they reveal some of their knowledge. Equally important are observations of distant planetary systems. For example, a few years ago, the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope observatory captured the formation of a distant planetary system in a snapshot for the first time. “Our goal for the next years is to first describe the formation of the Solar System and other known systems. In a second step, we want to understand which conditions and processes are responsible for the very different outcomes that planetary systems can reach at the end of their evolution”, says Drążkowska.
About the researcher and the excellence program
Joanna Drążkowska studied astronomy at the Nicolaus Copernicus University in Toruń (Poland) and received her doctorate from the University of Heidelberg. After research stays at the University of Zurich (Switzerland) and the Ludwig-Maximilians-Universität Munich (Germany), she has been leading the research group PLANETOIDS at MPS since 2022. In 2021, the journal Astronomy & Astrophysics honored the researcher with the Early Career Award. One year later, she received a Starting Grant from the European Research Council (ERC).
The Max Planck Society's Lise Meitner Excellence Program supports outstanding female scientists and offers them the opportunity to establish a permanent research group at a Max Planck Institute of their choice. The prerequisite for this is a positive evaluation of the group. The leaders of the Lise Meitner Groups are also considered candidates for future director positions at the MPG. There are currently 29 female scientists conducting research at the MPG as part of the Lise Meitner Excellence Program.