Classified by appearance
Hubble ‘tuning fork’
Clusters of Galaxies
Properties of galaxies
How do you find the distance?
d = v/H0
H0 is the Hubble constant is 22km/sec/Mly
All this needs to be calibrated – The Distance Chain
Explanation of Hubble’s Law The universe is expanding.
Finite speed of light means we look back into the earlier universe
Cosmological horizon – since the universe has a beginning
Masses of galaxies from rotation curves
Brightness from distance and photometry