Determine How Planetary-Disk Dynamics Shape the Small-Grain Halo

Determine how the vertical structures predicted for an inclined planet interacting with an exterior debris disk map onto the photogravitationally affected small-grain halo of β Pictoris, and explain why analogous structures are not clearly observed at longer wavelengths such as with ALMA.

Background

The observed convex/concave morphology of the outer halo resembles structures produced in theoretical models of an inclined planet interacting secularly with an exterior disk. However, the published models consider large planetesimals that are unaffected by radiation pressure, whereas HST/STIS traces much smaller grains in the photogravitational regime.

The theoretical models also produce a curving X-like structure on both sides of the star, while β Pictoris exhibits a one-sided Cat’s Tail. Thus, a definitive interpretation requires dynamical modeling that includes the full planetary system and radiation pressure, as well as an explanation for the apparent absence of comparable structures in longer-wavelength observations.

References

It therefore remains unclear how directly the predicted structures map onto the small-grain halo observed here, or why similar features are not apparent at longer wavelengths, such as with ALMA.

— Deep HST/STIS Coronagraphic Imaging of the $β$ Pictoris Debris Disk: On the Scattered Light Component of the Cat's Tail  (2609.30111 - Avsar et al., 24 Sep 2026) in Section 6.5, “Origins of β Pic’s Asymmetric/Warped Dust Halo”