Figure 2: Cartoon of the onset of dusty debris disk stability.

(Left) The sublimation radius (edge of red sublimation region) exceeds the Roche limit (blue) around young, hot white dwarfs, preventing the formation of dusty debris disks that are stable against sublimative destruction. (Middle) As the star cools, the sublimation radius recedes inward, and eventually crosses the Roche limit; at this critical temperature, dust in a debris disk would be minimally stable against sublimation. (Right) As the star continues to cool, the stable region for debris disks expands to include regions closer to the star.