The good news is that in astronomy there are methods to find the luminosity or absolute magnitude of a star, which will enable us to calculate the distance. This is why we did develop the basic method above.
Celestial objects of which we (think we) know the luminosity or absolute magnitude are termed Standard Candles.
Any object that can be considered as a Standard Candle in astronomy needs to have the following properties:
- it must be easy to identify and not being confused with a different type of object
- it must have a known luminosity related to some physical property that we can measure
- it should preferably be very bright so we can use it to large distances.
Fortunately there are several ways in which we can find estimates for a star’s luminosity. These methods are generally deducted from particular physical processes in a star (or entire galaxy) that are indicative for the object’s luminosity. These techniques allow us to estimate distances, even at inter-galactic scale.
In our EBook Stellar Distance these and other methods in Astronomy are discussed in detail.
The particular methods that use the Distance Modulus method described above
are Spectroscopic Parallax and Main Sequence Fitting .