Question

Imagine that you have obtained spectra for several galaxies and have measured the redshift of each galaxy to determine its speed away from us. Here are your results: Galaxy 1: Speed away from us is 15000 km/s. Galaxy 2: Speed away from us is 20000 km/s. Galaxy 3: Speed away from us is 25000 km/s. Estimate the distance to each galaxy from Hubble’s law. Assume that H0=22km/(sMly).

Answer 1

Distance of galaxy 1 = 681.82 Million light years.

Distance of galaxy 2 = 909.09 Million light years

Distance of galaxy 3 = 1136.36 Million light years.

Step-by-step explanation:

Given that Hubble constant is 22km/s/Mly

Galaxy 1 is speed away from us is 15000km/s

Galaxy 2 is speed away from us is 20000km/s

Galaxy 3 is speed away from us is 25000km/s

We have to find distance to each galaxy from Hubbles law.

According to Hubbles law , when galaxies move away from each other the velocity with which they recede ie the red shift in spectra of distant galaxies is proportional to the distance.

Distance=Velocity/Hubble constant

Distance of galaxy 1 =
`(15000 km/s)/(22km/(sMly).)` = 681.82 Million light years.

Distance of galaxy 2 =
`( 20000 km/s)/(22km/(sMly).)` = 909.09 Million light years.

Distance of galaxy 3 =
`( 25000 km/s)/(22km/(sMly))` = 1136.36 Million light years.