Redshift measurements of a galaxy yield a recession of 1000 km/s.Hubble's constant H is 23 km/s/10⁶ c·y.The distance to the galaxy is approximately A)23 $\times$ 10⁶ c·y B)37 $\times$ 10⁶ c·y C)44 $\times$ 10⁶ c·y D)52 $\times$ 10⁶ c·y E)61 $\times$ 10⁶ c·y

Question

Quizplus · Accepted Answer

By Hubble's law, we have v = Hd, where v is the recession velocity, H is Hubble's constant, and d is the distance to the galaxy. Rearranging this equation gives d = v/H = 1000 km/s ÷ (23 km/s/Mpc) = 43.5 Mpc = 44 x 10^6 pc = 44 x 10^10 km = 44 x 10^10 x 10^16 m = 44 x 10^26 m = 44 x 10^6 x 3.09 x 10^19 km = 44 Mpc. Therefore, the distance to the galaxy is approximately 44 x 10^6 pc, which corresponds to choice C.

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