Gas surface density distributions from hydrodymanic simulations using (left) α = 5 × 10⁻⁵ and (right) α = 5 × 10⁻⁴. The Jupiter-mass planet (located at X = 20 au and Y = 0 au in the plot) opens three gaps in the low-viscosity disk, while it opens only one gap in the large-viscosity disk. See Figure 5 for azimuthally averaged profiles of the gas surface density.