The Extragalactic Distance Scale
Many galaxies are
typically millions or billions of parsecs from our galaxy.
Typical distance
units:
Mpc = megaparsec = 1
million parsecs
Gpc = gigaparsec = 1
billion parsecs
Distances of Mpc or even
Gpc ó The light we see has left the galaxy millions or billions of
years ago!!
ó “Look-back times” of millions or billions of years
