A Question On Redshift

  • #1
elliottmarter
15
0
A redshift survey has identified a galaxy cluster for which it infers a di stance of 520 Mpc. At what redshift is this cluster observed to be? You may use H0 = 72 km s−1 Mpc−1

Now call me old fashioned but don't i need some kind of relativistic speed to calculate the redshift, i mean i have a distance of 520Mpc (=16.12x10^21m) and the hubble constant...but im sure i need a value for how fast its travelling away from me...

Thanks

EDIT i think i just realised that i times its distance by Ho to get its speed as its Kms-1 Mpc-1
 

Answers and Replies

  • #2
nickjer
674
2
Your edit is correct.
 
  • #3
mgb_phys
Science Advisor
Homework Helper
7,819
15
Then as long as this speed is much less than 'c' you can just use classical redshift.
When you get redshifts approaching (or larger than) 1 you need to take into account the expansion of the universe.
 
  • #4
elliottmarter
15
0
yeah the Lorentz factor was 1.00... so i just used z=v/c
 

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