# Has the dust clump in the debris disk of Beta Pictoris moved?

**Authors:** Yinuo Han, Mark C. Wyatt, William R. F. Dent  
**arXiv:** [2301.06891](https://arxiv.org/abs/2301.06891)  
**Date:** 2023-01-17  
**Summary page:** https://www.summarizepaper.com/en/paper/2301.06891v1/

## Key points

- Beta Pictoris star system has an edge-on debris disk with an unusual brightness asymmetry in the form of a dust clump
- Two theories proposed to explain the origin of the clump: planet migration trapping planetesimals into resonance or collision/tidal disruption of a planet-sized body
- Li et al. (2012) measured displacement of the dust clump over 12 years and found it to be $0.2^{+1.3}_{-1.4}$ au away from the star based on median and 1$\sigma$ uncertainty, with constraints on this displacement being <11 au at the 3$\sigma$ level
- Keplerian motion and resonant motion are both incompatible with observed motion at 2.8$\sigma$ and 2.6$\sigma$, respectively
- New mid-infrared observations using VLT/VISIR in September 2015 suggest that although Keplerian motion and resonant motion are still possible explanations for the observed dust clump's origin, it is more likely stationary than moving significantly away from its original position relative to Beta Pictoris' star system center point.
- Continued observations are important to better understand behavior of dust clump in Beta Pictoris' debris disk.

## Summary

The Beta Pictoris star system is known for its edge-on debris disk, which displays an unusual brightness asymmetry in the form of a dust clump. The origin of this clump has remained uncertain, with two classes of theories proposed to explain it. One theory suggests that a planet migrating outwards may trap planetesimals into a 2:1 resonance, resulting in the observed clump at pericentre of their orbits that trails the planet. The other theory suggests that the dust clump could originate from the collision or tidal disruption of a planet-sized body, or from secular perturbations due to a planet that create regions with enhanced densities in the disk. To discern between these two theories, Li et al. (2012) measured any projected displacement of the dust clump over a 12-year period and found it to be $0.2^{+1.3}_{-1.4}$ au away from the star based on median and 1$\sigma$ uncertainty, with constraints on this displacement being <11 au at the 3$\sigma$ level. This implies that Keplerian motion and resonant motion are both incompatible with the observed motion at 2.8$\sigma$ and 2.6$\sigma$, respectively. To obtain more robust constraints on any proper motion, new mid-infrared observations were conducted using VLT/VISIR in September 2015 to compare with previous observations made using T-ReCS camera on Gemini South Telescope. The B11.7 filter was used as it had consistent wavelength coverage with Si5 filter used previously and data reduction procedures were carried out consistently across all observations to ensure sub-pixel level precision required to track any small motion of the dust clump as expected by Li et al.(2012). Results from these new observations suggest that although Keplerian motion and resonant motion are still possible explanations for the observed dust clump's origin, they suggest that it is more likely stationary than moving significantly away from its original position relative to Beta Pictoris' star system center point.. Overall, this study provides further insight into the origin of the dust clump in Beta Pictoris' debris disk and highlights the importance of continued observations to better understand its behavior.