Measuring distances in astronomy.

We have seen that to understand our Galaxy and the rest of the universe, we need to know how far away things are. How do we do that?

For distances within our Galaxy and beyond, we have two main methods.

  1. The foundation of distance measurements is stellar parallax.
  2. Given the luminosity of a ``standard candle'', a measurement of its apparent brightness gives its distance.

Two kinds of standard candles

  1. There is a relation between surface temperature and luminosity for most stars -- those on the ``main sequence.''
  2. There is a relation between the period and luminosity for Cepheid variable stars.

Some history
