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Unformatted text preview: a) Consider a distant Quasar with an absorption feature at 160 nm. If we think this is due to the Lyman alpha absorption line that is normally at 122 nm what is the redshift of the gas cloud that is producing the absorption line? b) Assuming Hubbles expansion law holds, how far away from the Milky Way is the gas cloud? 4. a) The Virgo cluster is observed to have a recessional velocity of 1250 km/s. Estimate the distance to the Virgo cluster using Hubbles Law, v = H d , with H = 70 km/s/Mpc. b) For H = 70 km/s/Mpc, the critical density of the universe is crit = 9 10-27 kg/m 3 . Assuming that the density of the universe is the critical density, calculate the mass contained in a sphere centred on the Virgo cluster and extending out to the Milky Way using the distance you just estimated. c) Calculate the escape velocity from the surface of this sphere....
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- Spring '11