A standard candle is an object whose luminosity can be inferred from other observables (such as its spectrum or pulsation period). Once the luminosity is inferred, we need only measure its flux (or apparent magnitude) to determine the distance.wolram said:What is a standered candle ?
Chemical makeup is only one example of a parameter that might be used to infer an object's luminosity. The way that standard candles are calibrated is by observations of nearby objects for which distances can be obtained by other means. For example, if I measure the parallaxes of a bunch of stars near the sun and find their luminosities, I can look for trends between luminosity and other properties -- say, pulsation period and spectral type. If I then observe a much more distant object (for which there is no parallax), I can infer that object's luminosity by simply measuring the pulsation period and spectral type. Once I've inferred the luminosity, it's only a matter of plugging into the equation:a candle can burn with brightness according to its
chemical makeup, which do we know first ?