University Physics Notes: The Universe, Stars and Cosmology – The Cosmic Distance Scale
We can estimate the distance of the nearest objects to us in the Universe by measuring the shift in their position relative to the background stars as the Earth moves around the Sun (parallax),
The distance to more distant objects can be estimated using the
known relationship between luminosity and period for a class of stars
called cepheid variables, and more distant objects too can be placed
by using supernovae – a certain class of which explode with a
standard brightness and use the relationship
where
is
the intensity of the received light on Earth. Ultimately we can use
the redshift,
which
expresses the velocity of objects in terms of the a change in
wavelength due to the expansion of the Universe:
then
use Hubble's Law
to
find the distance.