Conditions for Hill-sphere unbinding during inward migration

Establish under which conditions Hill-sphere unbinding suppresses gas-giant formation and quantify how strongly the pebble flux must decline for Hill-sphere shrinkage to dominate over gas accretion.

Background

The models indicate that inward migration around low-mass stars can shrink a planet’s Hill sphere faster than the envelope can be replenished, potentially causing atmospheric loss and preventing crossover. The authors leave unresolved the parameter conditions governing this process, including the required decline in pebble flux.

References

It also remains to be established under which conditions Hill-sphere unbinding effectively suppresses gas giant formation and how strongly the pebble flux must decline for Hill-sphere shrinkage to dominate over gas accretion.

— Beyond Pebble Isolation: Diverse Pathways to Giant Planet Formation Across Stellar and Orbital Scales  (2609.09382 - Peerani et al., 8 Sep 2026) in Section 7, “Limitations and Future Work”