hwk9 - H atoms at the current time z = 0(b Calculate the...

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AST371 - Introduction to Astrophysics Assignment 9 - Nov. 16, 2009 1. Starting with the original formulation of Hubble’s Law, v = H 0 D (1) show that, in the limit of z ± 1, Hubble’s law can be approximated as cz = H 0 D (2) where z is the redshift parameter corresponding to a source with relative velocity v with respect to the observer on Earth. 2. Problem 24.22 from the textbook. 3. Consider a flat universe, and that all matter is in the form of atomic hydrogen. (a) Calculate the density of
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Unformatted text preview: H atoms at the current time ( z = 0); (b) Calculate the density of H atoms at z =10; (c) Assume that a photon of λ = 21 cm was emitted when the universe was 10 times smaller (in diameter) than it is now. Calculate the wavelength of the photon detected at Earth now. (d) Assume that the Hubble constant is H = 70 km s-1 Mpc-1 . Calculate the Hubble parameter H ( z ) when z = 10. 4. Problem 29.10 from the textbook...
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