*4.3. Classifying Standard Candles*

We above stressed that physical laws underlying a particular astronomical object permit one to know the luminosity of standard candles. Clearly, such rules are essentially based on thermodynamic or chemical processes of a given astrophysical object. Consequently, one can classify standard candles by means of these physical laws and, according to the simplest classification scheme, we can handle at least two kinds of standard candles summarized below [117].

