Finding Hubble’s Constant Joey Schmissrauter

Hubble’s Law v = H 0 d, where v is velocity in km/s, H 0 is a constant and d is a distance in Mpc. The units of H 0 are km*s -1 *Mpc -1

The Cepheid Distance Scale Leavitt’s Period-Luminosity relation M = -2.81log 10 P d Where M is the average absolute visual magnitude and P d is the pulsation period in days.

Expanding Universe and Redshift We can calculate the speed of recession using the redshift z. – Z = (λ obs -λ rest )/λ rest – Z = ((1+v r /c)/(1-v r /c)) 1/2 – 1 – V r /c = ((z+1) 2 – 1)/((z+1) 2 + 1) d ≅ (c/H 0 )*((z+1) 2 – 1)/((z+1) 2 + 1)

H 0 = 100*h km*s -1 *Mpc -1

Cosmic microwave background (CMB) [h] WMAP = 0.71 ± ~.03 [H 0 ] WMAP = 2.30 X s -1

Hubble time d = v*t H = H 0 *d*t H d = H 0 *d*t H 1 = H 0 *t H 1/H 0 = t H t H = 1/(3.24 X h -1 ) t H = 9.78 X 10 9 h -1 yr