Question

Suppose that you measure a galaxy's redshift, and from the redshift you determine that its recession velocity is 30,000 (3×10^4) kilometers per second. According to Hubble's law, approximately how far away is the galaxy?

Answer 1

Answer:

1.4 billion light years away

Explanation:

v = Recessional velocity = 30000 km/s[/tex]

$H_0$ = Hubble constant = $\frac{65}{3.2\times 10^6}\ ly$

D = Distance to the galaxy

According to Hubble's law

$v=H_0D\\\Rightarrow D=\frac{v}{H_0}\\\Rightarrow D=\frac{3\times 10^{4}}{65}\times 3.2\times 10^6\\\Rightarrow D=1476923076.92307\ ly\\\Rightarrow D=1.4\times 10^9\ ly$

The galaxy is 1.4 billion light years away