If the distance of a galaxy at a redshift z 0.5 is 1,800 Mpc,how many years back into the past are we looking when we observe this galaxy?
A)500 million years
B)2 billion years
C)6 billion years
D)9 billion years
E)10 billion years

Question

Quizplus · Accepted Answer

The formula to calculate the age of the universe at a given redshift is t = (1/H0) x (1/z) x (1 - sqrt(Omega_m /(1+z))), where H0 is the Hubble constant, Omega_m is the density parameter of matter, and z is the redshift. Assuming H0 = 70 km/s/Mpc and Omega_m = 0.3, we can calculate the age of the universe at a redshift of 0.5 to be approximately 6 billion years. Therefore, when we observe this galaxy, we are looking back approximately 6 billion years into the past.

If the Distance of a Galaxy at a Redshift Z