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Astro 405/505, fall semester 2005 Additional problems Problem 1: plasma You intend to study a gas cloud that collapses to form a star. Suppose the cloud has a radius R = 10 15 cm, a temperature T = 1000 K, a density of neutral atoms n n = 10 12 cm - 3 , and a density of ionized atoms (and electrons) n e = 10 8 cm - 3 . Explain with what technique you would describe the collapse. Problem 2: emission spectra Suppose an emission region is homogeneous and the radiation coeFcients have the following form: j ν = A ν - 1 α ν = B ν - 3 σ = 0 A, B = const . Calculate the angular distribution of the intensity, I ν , that would be seen by an observer at a ±xed position at a distance D from the emission region, and the total ²ux. a) Assume the emission region has the form of a cube with sidelength R , that is observed exactly along the normal of one of the sides. b) Assume the emission region has the form of a sphere with radius R . Problem 3: stellar emission

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