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  1. In astronomy, the term "disk" may be applied to a flattened, circular region of gas, dust, and/or stars. It may refer to material surrounding a newly-formed star, material accreting onto a black hole or neutron star, or the large region of a spiral galaxy containing the spiral arms.

  2. A disk is also the apparent circular shape of the Sun, a planet, or the Moon when seen in the sky or through a telescope.

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