CLOUDY modeling of weird Far-IR emission in the central zone of the Helix Nebula

We present the results of CLOUDY modeling of the central zone of the Helix Nebula. Our aim was to match the observed, excess far-infrared emission. Our best fit models fill the central zone with 1$μ$m-sized grains, with a gas-to-dust ratio of 500, where precise composition is unimportant. We speculate on the origin of these grains.