# AGN accretion disk vs. torus

The torus is the donut of dust encircling the Active Galactic nucleus. The accretion disk is inside the torus. Is there a boundary between the two? At what point does a torus become an accretion disk? What are their differences?

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The Figure above is Figure 1 of this paper. It shows the scales of various features of the unified AGN model in units of $\log_{10}(r/\text{pc})$. Remember that a parsec is about 3.26 light-years or 200,000 AU (or 5000 times Pluto's mean orbital distance). The $10^{-5}$ mark is roughly the Schwarzschild radius for a $10^8\text{M}_\odot$ black hole.