# A possible misaligned orbit for the young planet AU Mic c

**Authors:** H. Yu, Z. Garai, M. Cretignier, Gy. M. Szabó, S. Aigrain, D. Gandolfi, E. M. Bryant, A. C. M. Correia, B. Klein, A. Brandeker, J. E. Owen, M. N. Günther, J. N. Winn, A. Heitzmann, H. M. Cegla, T. G. Wilson, S. Gill, L. Kriskovics, O. Barragán, A. Boldog  
**arXiv:** [2411.16958](https://arxiv.org/abs/2411.16958)  
**Date:** 2024-11-25  
**Summary page:** https://www.summarizepaper.com/en/paper/2411.16958v1/

## Key points

- The AU Microscopii planetary system, at 24 million years old, provides insights into early dynamical history of planetary systems
- Researchers measured the Rossiter-McLaughlin effect for planet AU Mic c to determine its sky-projected spin-orbit angle
- Spin-orbit angle of planet c found to be around 67.8 degrees with a margin of error
- Possibility that planet c may be misaligned with respect to inner planet b and host star's equatorial plane raises questions about system dynamics
- Misalignment could be due to secular interactions or giant impact event, potentially impacting system stability
- Further observations needed to refine understanding of planet c's spin-orbit angle and high density
- Additional data required to confirm alignment of planets in transit and explore reasons for any observed misalignment further
- Study emphasizes complexities within young planetary systems like AU Microscopii and importance of continued research for better understanding formation and evolution processes

## Summary

The AU Microscopii planetary system, at only 24 million years old, offers valuable insights into the early dynamical history of planetary systems. In a recent study, researchers conducted the first measurement of the Rossiter-McLaughlin effect for the warm sub-Neptune planet AU Mic c. By observing two transits simultaneously with VLT/ESPRESSO, CHEOPS, and NGTS, they were able to determine the sky-projected spin-orbit angle of planet c to be in the range of 67.8 degrees with a margin of error. This provides crucial information about how this young planetary system formed and evolved. Interestingly, the study also explored the possibility that planet c may be misaligned with respect to both the orbit of the inner planet b and the equatorial plane of its host star. This potential misalignment raises questions about the system's dynamics and could be explained by secular interactions with other bodies in the system or a giant impact event. However, it is noted that a significantly misaligned orbit for planet c may pose challenges to the overall stability of the system. Further observations are deemed essential to refine our understanding of planet c's spin-orbit angle and shed light on its high density. The researchers acknowledge that while seeing both planets in transit suggests some level of alignment, additional data is needed to confirm this and explore potential explanations for any observed misalignment further. In conclusion, this study highlights the complexities within young planetary systems like AU Microscopii and underscores the importance of continued research to unravel their mysteries and better understand their formation and evolution processes.