(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Hubble's law may be written as

H0dL = z +(1/2)(1 - q_{0})z^{2}

Working to O(z) only, what is the redshift of a galaxy at a luminosity distance of 100 Mpc

from Earth?

What is the role of the constant q0? Given that observations show that q0 = -0.77,

calculate the luminosity distance (in Mpc) of a high redshift supernova with z = 0.5.

2. Relevant equations

the first question is what O(z) might mean and second if i make the substitution ,q0 which is given later i get a quadratic equation with imaginary solutions.The second part is just a metter of calculations i suppose ,but it seems that for the first question im missing something.

3. The attempt at a solution

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# Homework Help: Luminosity distance

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