# Planet Formation Theory in the Era of ALMA and Kepler: from Pebbles to Exoplanets

**Authors:** Joanna Drazkowska, Bertram Bitsch, Michiel Lambrechts, Gijs D. Mulders, Daniel Harsono, Allona Vazan, Beibei Liu, Chris W. Ormel, Katherine Kretke, Alessandro Morbidelli  
**arXiv:** [2203.09759](https://arxiv.org/abs/2203.09759)  
**Date:** 2022-03-18  
**Summary page:** https://www.summarizepaper.com/en/paper/2203.09759v2/

## Key points

- Planet formation theory has advanced significantly in recent years due to improved observational capabilities.
- Classical planet formation theory has been revised to account for the observed diversity of exoplanetary systems.
- A group of researchers summarize the latest developments in planet formation theory in a review chapter accepted by Protostars and Planets VII.
- The chapter covers various aspects of planet formation theory, including dust evolution and growth of planetary cores through accretion.
- There are preferential locations for the formation of planetesimals and planets in circumstellar disks, with a significant fraction of solids not growing past pebble-sizes outside these locations.
- Massive planetary cores emerge over different timescales within one disk, with evidence that the first planetary cores start forming early during circumstellar disk buildup processes.
- State-of-the-art models for diverse planetary system formations are reviewed, including population synthesis approaches necessary to compare theoretical model outcomes with exoplanet populations.
- Many exoplanetary systems could have formed differently from our own Solar System according to these models.
- Observations from ALMA and Kepler missions provide new constraints on the process of planet formation.

## Summary

The field of planet formation theory has undergone significant advancements in recent years, thanks to the increasing observational capabilities of young stars and their surrounding disks. The classical planet formation theory, which was developed based on our Solar System, has been revised to account for the observed diversity of exoplanetary systems. In this review chapter accepted by Protostars and Planets VII, a group of researchers summarize the latest developments in planet formation theory. The chapter covers various aspects of planet formation theory, from dust evolution to the growth of planetary cores through accretion of gas, pebbles, and planetesimals. The authors highlight that the process of planet formation may not be spatially uniform in circumstellar disks; there are preferential locations for the formation of planetesimals and planets. Outside these locations, a significant fraction of solids does not grow past pebble-sizes. The reservoir of pebbles plays an important role in the growth of planetary cores through pebble accretion. The review also emphasizes that massive planetary cores emerge over different timescales within one disk. Additionally, there is growing evidence that the first planetary cores start forming early during circumstellar disk buildup processes. The state-of-the-art models for diverse planetary system formations are reviewed in detail, including population synthesis approaches necessary to compare theoretical model outcomes with exoplanet populations. The authors note that such models have shown that many exoplanetary systems could have formed differently from our own Solar System. Overall, this review provides a comprehensive overview of recent developments in planet formation theory and highlights new constraints on the process brought about by observations from ALMA and Kepler missions. These findings will help us better understand how planets form around other stars beyond our Solar System.