An astronomer measures a galaxy to have an apparent recession velocity of 2,100 km/s.How far away is the galaxy? A) 300 Mpc B) 30 Mpc C) 300 kpc D) 1.4 x 10⁵ Mpc

Question

Quizplus · Accepted Answer

This question involves using the Hubble's Law equation: v = H0d, where v is the apparent recession velocity, H0 is the Hubble constant, and d is the distance to the galaxy. Rearranging the equation for d, we get d = v/H0.

Using the given value of v = 2,100 km/s and a common value of H0 = 70 km/s/Mpc, we get

d = 2,100 km/s / 70 km/s/Mpc = 30 Mpc

Therefore, the best choice is B) 30 Mpc.

An Astronomer Measures a Galaxy to Have an Apparent Recession