Quote:
Originally Posted by hobbit
Sometimes I see the distance to an object given as a redshift value. How does this correspond to the distance in lightyears? ie redshift of 1=100 lightyears.
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D = zc/H0
where
D = distance
Z = redshift cosmological value
c = speed of light
Ho = Hubble constant 71 Km s expansion per Mpc (per mega parsec).
You need to dimensional analysis to ensure values are the same like c = Kms
Because distance values get so large in metres, km parsecs or mega parsecs or lightyears, then redshift is often referred to as the distance z. The greater the cosmological redshift the greater the distance that object is.
Do not confuse cosmological redshift to wavelength redshift of local galaxies/objects. They have local motion/movement (as well as cosmological redshift movement expansion) that is perciliur to their cluster so their cosmological redshift is more difficult to determine. At high velocities the value of z becomes relativistic opening a whole world of hurt in obtaining their distances.