Astro 201: Exercise: Hubble Law

For the following problems, assume that H₀ = 50 km/s/Mpc.

1. What method from chapter 5 does one use to get the velocity of a galaxy?

2. About how far away is a galaxy with velocity 7000 km/s?

3. How fast is a galaxy moving away from us if it is 1000 Mpc distant?

4. The Andromeda galaxy is 0.77 Mpc away. Calculate its expected radial velocity. In fact, the Andromeda galaxy is coming toward us at about 200 km/s. Why? What is going on?

Answers