Properties of Model Comae around Kuiper Belt and Centaur Objects

Abstract

The cometary activity of Chiron inspires us to investigate observable lifetimes of hypothetical dust particles around large, distant Centaur and Kuiper Belt objects (KBOs). Our model computes dust particle trajectories assuming comet nucleus gravity, solar gravity, and solar radiation pressure. We find that particle lifetimes are extremely sensitive to the magnitude of the initial velocity. Long-lived orbits require an exact combination of nucleus size, heliocentric distance, particle size, and initial velocity. Estimating ejection velocities due to CO sublimation, we find that particles escape >50,000 km from Centaurs in ≲6 days and from KBOs in ≲10 days. Assuming optimal ejection velocities <vescape, upper limits to bound coma lifetimes are 50–75 days for Centaurs with Chiron-like activity. Thus Chiron's long-lived coma cannot be a result of an outburst. To observe a KBO coma requires a massive ∼5 × 109-kg dust coma, and its lifetime varies from <2 months to ∼1 year depending on object size and heliocentric distance.